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Introduction to waterproof and water repellent textiles
Introduction to waterproof and water repellent textiles
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Carmen Loghin, Lumința Ciobanu, Dorin Ionesi, Emil Loghin, Irina Cristian “Gheorghe Asachi” Technical University of Ias¸i, Ias¸i, Romania
1.1
Introduction
Protection against environmental factors is the initial function of clothing. In a wet environment, the basic requirement for garments is to keep the wearer dry by being waterproof and or water repellent. The difference between the two terms is essential when characterizing the behaviour of textile materials in reference to liquid water. In contact with water, water repellent materials form drops that can be easily removed from the fabric surface but for longer contact with water or with a higher pressure difference, the material will absorb water. Water repellent textiles are often high density woven materials made of very fine yarns or common materials with hydrophobic surface treatment. Waterproofing is defined as the property of a material not to be penetrated by fluids. The waterproofness of a fabric can be measured using two testing methods: one that simulates raining and the other (more common) that subjects the fabric to hydrostatic pressure. The minimum value for the hydrostatic pressure without leaking at its surface, at which a fabric is considered rainproof is 5000 mm water column, while for waterproof materials the hydrostatic pressure can reach 10,000–15,000 mm water column (Loghin, 2003). For high quality waterproof materials designed for aggressive conditions, the hydrostatic pressure varies between 15,000 and 30,000 mm water column. Such fabrics are completely waterproof even under very high pressure. First historical mentions regarding the hydrophobization of textiles are in the 15th century, when sailors tried to obtain sea water protective clothing by impregnating it with linseed oil, animal fat or wax. The first bio-inspired waterproof clothing product (kamleika) belongs to Aleut American Indians who used dried seal or whale intestines; the seams have been sealed with animal glues to make the product totally waterproof (Lynch and Strauss, 2015). The first waterproof fabric was produced and patented by Charles Macintosh in 1823 in England (Shephard, 2012). The process to produce waterproof materials involves the spreading of a rubber layer between two woven fabrics. The problems related to the use of garments made of this material, caused by the unstable rubber, were eliminated by the process of rubber vulcanization that led to a textile material more stable in environmental conditions. The process was patented in 1844 by Charles Goodyear in the United States, and Thomas Hancock in England. For a long period, rubberized textile fabrics were the raw material for waterproof garments. The main problem with these garments is reduced comfort due to the Waterproof and Water Repellent Textiles and Clothing. https://doi.org/10.1016/B978-0-08-101212-3.00001-0 Copyright © 2018 Elsevier Ltd. All rights reserved.
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Waterproof and Water Repellent Textiles and Clothing
overheating of the wearer’s body and high resistance to vapour passing out through the clothing layers. The sweat vapours condense in contact with the interior surface of the clothing, humidifying the textile layers in direct contact with the skin and causing increased discomfort. Subsequent researches conducted in the production of waterproof textiles led to a new type of material, waterproof-breathable fabrics. Ventile fabrics are waterproof, breathable, densely woven materials developed in the UK during WWII to replace flax in garments for outdoor, military, medical and work wear applications. The first microporous membrane (polytetrafluoroethylene PTFE, also known as Teflon) was created in 1969 by W. L. Gore and Associates. The first GORE-TEX materials appeared on the market in 1976, starting a revolution in the concept of waterproof-breathable garments. Water repellent textiles are obtained using specific finishing surface treatments. A review by Schuyten et al. (1948) shows that these hydrophobic treatments were developed significantly starting with 1920s. Waterproof-breathable textiles represent a significant global market, with major players from the US, Europe and Asia. A press release for a report from Grand View Research Inc. (2016) indicates the value of the waterproof breathable textiles market in 2014 was $1.43 billion. Membrane waterproof-breathable products account for 71% of the overall demand, while garments remain the main application. The report anticipates a constant growth of this market, stimulated by the need for comfortable multifunctional products, the use of innovative technologies to produce biomimetic and smart textiles, and the focus on recyclable and eco-friendly products. With an estimated compound annual growth rate (CAGR) over 5% per annum, the market of waterproof-breathable textiles is expected to reach $2.18 billion by 2020.
1.2
Areas of application of waterproof and water repellent textiles
Waterproof and water repellent materials are currently used in the three major textile areas (clothing, home and outdoor products and technical textiles). There are a large number of possible applications, from rain garments to medical and military equipment (Singha, 2012). Regardless of the applications for which waterproofness is the determinant function, the complexity of the conditions during use requires the multicriterial design of the fabric structure and its testing to ensure a high number of functional characteristics such as: vapour permeability, tensile strength, abrasion resistance, flexural strength (repeated cycles), resistance to low and high temperatures, resistance to light, chemical resistance and more. Several standards are used for the evaluation of waterproof-breathable and water repellent textiles. Waterproofness is measured as the hydrostatic pressure needed to penetrate the waterproof-breathable fabrics. The standards used for determining waterproofness are: – ASTM D 3393-91 Standard Specification for Coated Fabrics—Waterproofness. – AATCC TM 127-water resistance: hydrostatic pressure test.
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– ISO 811 Textile fabrics—Determination of resistance to water penetration—Hydrostatic pressure test. – BS 3424-26 Testing coated fabrics. Methods 29A, 29B, 29C and 29D. Methods for determination of resistance to water penetration and surface wetting.
Breathability is evaluated based on water vapour transmission (WVT). There are several test methods, applicable to both coated and laminated fabrics: (1) The upright cup test—JIS L 1099, JIS Z 0208, ISO 2528, Desiccant Method of ASTM E96, JIS K 6328. (2) The inverted cup method—JIS L 1099, similar to ASTM E96-BW test method. (3) The sweating hot plate method (evaporative resistance)—ISO 11092, ASTM F 1868. (4) The dynamic moisture permeation cell—ASTM F 2298.
Water repellency is tested using the following standards: – – – –
AATCC TM 22-water repellency: spray test. ISO 9865-water repellency: Bundesmann rain shower test. AATCC TM 35-water resistance: rain test. ISO 22958:2005 Textiles—Water resistance—Rain tests: exposure to a horizontal water spray. – EN 14360-rain test (test method for ready-made garments). – AATCC TM 42-water resistance: impact penetration test.
1.2.1
Clothing design specifics according to the end use
Garments remain the most frequent use of waterproof and/or water repellent fabrics. Due to the complex requirements of the users (protection, comfort, aesthetic, identity, etc.), waterproof materials must have a sum of properties that ensure the multifunctional characteristics of the garment. The level of performance of the waterproof and water repellent materials used for garments is determined by two groups of factors: (i) subjective variables, defined by the requirements and the level of comfort of the final user and (ii) objective variables, defined by the environmental conditions, risk factors and specifics of the activities carried out by the user. A first level of classification for waterproof clothing contains: – – – –
conventional wet-weather clothing; work clothing and uniforms (including military); clothing for sport and leisure; and personal protective equipment (PPEs) (for risk conditions).
The main problem when using waterproof fabrics for garments is the comfort of the wearer. Usually, waterproof technologies consisted in covering and blocking the pores of the textile substrate so water absorption and transfer from the exterior towards the body are no longer possible. This way, the material acts like a barrier for the humidity in the environment, apparently satisfying the protection function of the garment. In the relationship between the human body, the garment and environment, the transfer of humidity must be analysed in both directions from and towards the body. Human skin sweats continuously, both at rest (insensible perspiration or perspiratio insensibilis),
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Waterproof and Water Repellent Textiles and Clothing
or in activity (sensible perspiration). For example, during intense effort the average human body (with a 1.8 m2 skin surface) produces approx. 1000 cm3 perspiration per hour to reach its thermal balance (Holmes, 2000). The humidity produced through perspiration must be eliminated as vapour in a process of mass transfer through the layers of the garment. This problem was solved in the 1980s by the production of waterproof-breathable textiles, which are materials waterproof for liquid water in the environment but permeable to sweat vapours from the body passing through clothing layers (Section 1.3.3.3).
1.2.1.1
Conventional wet-weather clothing
Conventional garments are used in wet environments (rain and snow) and their waterproofness is determined by special characteristics of the materials. The basic material can be water repellent for short periods of rain or snow, or waterproof and water repellent for long exposures to rain or snow. This type of garment includes: – waterproof garments (raincoats, jackets, trousers); – waterproof garments with high thermal insulating characteristics and low weight (e.g. equipment for winter sports); – waterproof bioactive garments (insect repellent, antiallergic, antibacterial) to be used in outdoor activities in insect-infested environments, and in medical applications where the risk for infections is very high; – waterproof UV garments for outdoor sports (fishing, camping, hiking, etc.), as well as work wear for workers exposed to UV; and – low maintenance products with increased cleaning characteristics (e.g. work wear, clothing for children, etc.).
Work clothing, including uniforms, can be considered conventional waterproof garments, used in similar conditions but only in the working period. The fundamental aspects that have to be taken into consideration when designing a waterproof garment and subsequently the selection criteria (Loghin and Ciobanu, 2008; Mukhopadhyay and Midha, 2008a; Chinta and Satis, 2014) are: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
waterproofness level; fabric weight; level of thermal physiological comfort; the capacity to allow the transfer of sweat vapour; aesthetics; durability (strength to repeated flexural cycles, tear, tensile, friction strength); launderability (washing/dry cleaning/tumble drying); resistance of the water repellent treatment to repeated laundering and cleaning; visibility (for work wear); identification/identity (for uniforms); and flame retardant (for work wear and uniforms), etc.
Waterproofness and air (wind) resistance/proofness of the materials are the most important issues in the case of weather protective outer garments. For such garments, water/airproofness must be considered at constructive, structural and technological levels, as illustrated in Fig. 1.1.
Simplified geometry of the patterns Reducing the section lines of the basic elements (front, back, sleeves)
Constructive Number of elements
Increasing the number of functional elements used for: • Bottom lines • Sectioning of the main eolements and their partial replacement with nets • Closure systems • Pockets
Membranes Raw materials
Water repellent finishing Multicomponent (sandwich) structures
Special finishing
Structural, depending on
Waterproofing Secondary raw materials
Coated with polymers
Simplified technological structure of the garment elements
Technological
Introduction to waterproof and water repellent textiles
Particularities
Textile aspect (the textile material is visible on the front) Coated or laminated
Welding or bonding
Compact aspect (the textile material act as support)
Joining methods Mixt (sewing-welding or sewing bonding)
Fig. 1.1 Design characteristics for waterproof clothing. 7
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Waterproof and Water Repellent Textiles and Clothing
Designing a waterproof garment requires certain constructive solutions (geometrical pieces, few cut lines, most sealed constructive variants for closures and/or pockets) and technological processing (welding or bonding/ sealing, sewing and welding, sewing and sealing). Replacing sewing with welding technologies or the use of seam sealing are decisions essential for the garment quality, because the holes produced by the needles during sewing lead to diminished waterproofness.
1.2.1.2
Sport and leisure garments
The requirements for sport and leisure garments are similar to the ones for conventional clothing, but the functional performance level of the waterproof materials needs to be higher due to increased sweating in intense effort, requiring a higher moisture transfer rate from the body towards the exterior. For example, for an effort rate of 500 watts, the perspiration rate is approximately 800 g/hour (Mukhopadhyay and Midha, 2008b). The main part of this humidity transfers through the garment, the rest representing losses through ventilation and respiration. The results of athletes are often influenced decisively by the performance level of the clothing. The potential of waterproof and/or water repellent materials to be used for multifunctional sport garments is illustrated in the examples below: – – – –
waterproof garments for winter sports; self-ventilating waterproof garments; waterproof garments with moisture control; and antimicrobial and antifungal waterproof garments.
The basic requirements for waterproof sportswear and leisurewear are as follows, ranked in this order: 1. good heat and mass transfer capacity; 2. good vapour permeability in relation to air proofness; and 3. moisture control, assured by: humidity absorption and its transport towards the exterior (environment); keeping the skin dry; and quick drying after humidity absorption; 4. good dimensional stability in wet state; 5. aesthetic aspect; 6. low weight; 7. pleasant touch; 8. low maintenance; and 9. durability, etc.
1.2.1.3
Personal protective equipment
PPE represent a set of individual protective means (clothing, footwear, head protection, gloves, masks, etc.). Protective clothing must ensure complete or almost complete insulation from the environmental factors (weather, hazards), some of these factors are harmful to human health. In the conditions of hazardous environments, waterproofness is a major requirement that most of the time must be correlated with
Introduction to waterproof and water repellent textiles
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other requirements for the protective garment in specific working conditions. The complex protection requirements for the working and protective equipment and/or working environment can be as follows: 1. For work that involves fluid flow: the possibility for self starting or self blocking, spill, immersion-waterproof fabric, seam sealing, resistance to dynamic loads. 2. For work that involves microbiological cultures, bacteria, physiological fluids: impervious fabric, seam sealing, mechanical strength, decontamination capacity. 3. Outdoor work environment with low temperatures: thermal insulation, waterproof fabric, seam sealing. 4. Work environments with high humidity, precipitations, air currents: waterproof fabric, seam sealing. 5. Work environments with dangerous powders or suspensions of microorganisms: impervious fabric, seam sealing, decontamination capacity. 6. Gaseous work environment, toxic vapours, aerosols: impervious fabric, seam sealing, specific chemical resistance. 7. Gaseous work environment, inflammable vapours or explosives: impervious fabric, seam sealing, specific chemical resistance, antistatic properties, flame retardant characteristics. 8. Sterile work environment, clean rooms: impervious fabric, seam sealing, antistatic properties.
In the case of conventional clothing, waterproofness is perceived as the property of the materials to oppose the passing of air and water and therefore a measure of protection against atmospheric factors while ensuring the wearer’s comfort. It therefore needs to be breathable, not impermeable. In the case of protective clothing, waterproofness (imperviousness or impermeability) has many aspects, depending on the system of factors and leading to a specialization of the waterproof materials. The following types of impervious textiles can be listed: – – – – –
impervious to impervious to impervious to impervious to impervious to
1.2.2
water/air and permeable to water vapours; chemical agents; biological agents (microorganisms, physiological fluids); radioactive contaminants; and micro-particles generated by the human body, e.g. for clean rooms.
Home and outdoor textiles
Waterproof and water repellent textiles become more and more common in products used at home, as well as for the outside. For home textiles, main applications are pillow protectors, bed covers, bed sheets and mattress covers. Shower curtains can also be made from waterproof textile materials. Decorative mobile walls can also be made from this type of material. If needed, further treatments can be applied to the textile-coated materials, like antifungal, antidust mites and antibacterial, halogen-free fire retardant treatments (Sen, 2008). Home outdoor applications include small shade structures and other decorative outside elements, covers for chairs and tables in the garden, etc. Apart from clothing
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Waterproof and Water Repellent Textiles and Clothing
for outdoor activities, waterproof/water repellent materials are also used for specific equipment such as tents, backpacks, hiking gear, insect repellent curtains, etc.
1.2.3
Technical applications
There is a wide range of technical/functional applications that use waterproof or water repellent textiles including agricultural, civil engineering, medical, industrial and packing applications. In agriculture, waterproof-breathable textiles are used for different cultures (breathable ground cover for weed control, waterproof sheeting, root protective bags for transporting, greenhouse covers, tree shelters), as well as structures with agricultural use (leak-proof sheeting for water and liquid fertilizer tanks and flexible water tanks) and packing for product transport. Architectural textiles are lightweight, flexible materials that can be used for temporary and permanent structures. Waterproof coated or impregnated textiles can save energy and decrease costs, while allowing for innovative creative approaches to architecture. Water repellent treatments are also applied to such materials, especially for outdoor applications, to improve their behaviour in wet weather. Temporary applications using textile membranes (woven fabrics with PVC) include tents, clear-span structures, tension fabric structures and air structures and commonly built for exhibition spaces, structure for leisure activities, short-term commercial spaces, social gatherings, storage facilities, etc. Such materials are high strength woven fabrics made of glass, fibres, PES or polyethylene coated with PVC, silicone, PTFE ref (Houtman, 2015). Textile membranes are suitable for roofs due to their lower weight, controlled mechanical strength including impact, resistance to weather, controlled translucence, sound insulation capacity, fire retardant characteristics and resistance to UV (Zerdzicki, 2015). To increase their behaviour, a hydrophobic top coating can be added to the materials, while titanium dioxide (TiO2) photo-catalyst provide self-cleaning properties. Another advantage is that textile membrane roofs can be fixed or retractable. Another domain of application refers to decorative waterproof textiles like canopies, awnings, marquees, shading structures and advertising structures that are placed on buildings or are in the immediate public space. Waterproof textiles are widely used in medical applications, for nonimplantable and healthcare and hygiene products. Literature presents examples of waterproof breathable textiles (woven, knitted) used for orthopaedic orthoses to improve the level of comfort for patients, replacing the neoprene commonly used. Another orthopedic end-use is a knitted breathable cast for upper or lower limbs (Sherif and Roedel, 2011). Modern multilayer wound dressings have an outer layer (mostly nonwoven) that is waterproof-breathable. Healthcare products include wheelchair cushions, mattress covers, pillow protectors, bed-stretchers, stretchers and hospital cases. Another application is for surgical gowns and drapes. Apart from their characteristics, these products must also ensure a clean environment around the patients and medical staff, so the coating must include antifungal and antibacterial substances. The coating can also be designed to ensure viral protection, an important issue in hospitals.
Introduction to waterproof and water repellent textiles
1.3
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Basic aspects regarding waterproof and water repellent textiles
1.3.1
Textile and water interaction mechanism
Because waterproofness is a requirement imposed mainly by the environment (weather conditions), the behaviour of textile materials towards liquid water must be commented upon. From this point of view, textile materials can be divided into: 1. materials with water absorption and retaining characteristics—hydrophilic materials; 2. materials that repel water—hydrophobic materials.
The capacity of the textile surface to absorb or repel liquid water is explained through the surface tension developed at the interface between the water drop and textile surface (see Fig. 1.2). The surface tension γ 12 generated at the interface depends on the fibrous composition of the textile material, the structural parameters of the yarn and material and the microstructure of the contact area (smooth, micro rough, continuous, discontinuous, etc.) (Park et al., 2016). Another factor influencing the balance of the superficial tensions is the material’s porosity, namely the state of the transversal pores after water repellent finishes (open, blocked uni- or bilaterally). Fig. 1.3 presents the simplified structure of a textile material, emphasizing the transversal (PT), longitudinal (PL) and superficial (PS) pores. The behaviour of a textile material towards liquid water is evaluated based on the value of the contact angle (θ), with the following formula (Young’s Equation): cos θ ¼
γ 13 λ12 γ 23
(1.1)
where γ 12, γ 13 and γ 23 represents the surface (interfacial) tensions of the fabric-water (γ 12), fabric-air (γ 13), and water-air (γ 23) contact. Theoretically, the value of the contact angle is placed in the interval 0 angle and 180 angle. The textile materials can be classified accordingly into (Gugliuzza and Drioli, 2013; Zimmermann et al., 2009): g23
g13
Air (3)
q
Water (2) g12 Fabric (1)
Fig. 1.2 Surface tensions at the contact between the fabric and the water drop theoretical model. From Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh.Asachi Publishing House, Iasi, pp. 50–60, ISBN 973-99209-4-2. Published with the author’s permission.
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.3 The porous structure of a textile surface (simplified model). From Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh.Asachi Publishing House, Iasi, pp. 50–60, ISBN 973-99209-4-2. Published with the author’s permission. -
superhydrophilic materials, θ ! 0 angle; hydrophilic materials (including textiles), 0 angle < θ < 90 angle; hydrophobic materials (including textiles), 90 angle θ < 150 angle; superhydrophobic materials (including textiles), 150 angle θ 180 angle.
1.3.2
Water repellent textiles
Hydrophobic textiles present the advantage of air permeability but offer less protection against water, being generally used for conventional garments or as an exterior layer for waterproof clothing. Based on the resistance to cleaning agents, the hydrophobicity can be permanent (durable water repellent, DWR) or temporary (Gibson, 2008). Depending on the way the water repellent effect is obtained, there are two groups of textile materials: 1. inherent water repellent textile materials; 2. textile materials with water repellent finishing.
Water repellent characteristics are specific to compact textile structures. Inherent water repellent materials are (i) high density woven fabrics, made of very fine yarns and filaments and (ii) nonwoven materials. Microfibres and microfilaments present a high technological potential, with a practically unlimited area of applications (garments, household, medical and technical textiles) due to their special surface properties. In this group are included fibres with fineness 0.3–1 dtex, with the interval 0.3–0.1 dtex for super-microfibres. These fibres are made of synthetic polymers—PTE, PA, PP, PAN or cellulose (Purane and Panigrahi, 2007). The specific properties and implicitly the end-use are determined by the morphological structure of the microfibres and their specific technology. The properties of the woven fabrics controlled through the particular characteristics of the microfibres refer to:
Introduction to waterproof and water repellent textiles
-
-
-
13
water repellency and air impermeability due to the high density of the fabrics made of microfilaments (e.g. a fabric made of 0.2 dtex microfilaments has a thread density of 7000 microfilaments/cm2) (Kaynak and Babaarslan, 2012); the vapour permeability varies in acceptable limits due to the interstitial porosity of the textile surface; increased filtering/absorption capacity of solid particles in reference to other fibres determined by the significantly higher specific surface, given by the number of microfibres per unit area and the cross section geometry (segmented, cross or island type structure); and increased liquid absorption capacity concurrent with an increased drying rate due to the same bigger specific surface, intensifying the capillary activities at textile surface level.
The hydrophobization of the textile materials is carried out with different chemicals that ensure high superficial tension in relation to water. These substances orient their hydrophobic groups towards the textile fibres thus forming a protective brush against water. The water hydrophobization agent forces are null, facilitating the water drop to maintain its spherical shape without spreading onto the fibres. In general, the limitations of the water repellent treatments refer to low surface energy and extended surface porosity. The technological variants for hydrophobization include: 1. Hydrophobization with additives (aluminium organic salts, aluminium soaps, paraffin emulsions with aluminium salts). 2. Hydrophobization with resin type reactive agents (perfluoro ester-aziridine , zirconium compounds, radical crosslinking of methyl or cyanoethyl silicones (Indu Shekar et al., 2001) fluorocarbon (FC) resin (Kuhr et al., 2016)). 3. Hydrophobization through chemical modification of the fibres (esterification or etherification reactions). 4. Textile finishing with nanoparticles that create an ultrahydrophobic surface with selfcleaning characteristics (lotus effect). Oleophobization techniques give textile materials the property of repelling oils and thus creating a protection against dirt and smudges, while increasing the hydrophobization effect. FC resins are used as oleophobization agents—water emulsions or solutions in solvents (Kuhr et al., 2016). 5. Plasma treatment of the textile materials (Colleoni et al., 2015), plasma polymerization or plasma depositing of organic-silicone polymers (Kale and Palaskar, 2010) can give a hydrophobic character to materials that are typically not hydrophobic, like 100% cotton.
1.3.3
Waterproof textiles
An initial example of this type of materials is the high-density woven fabric VENTILE, made of 100% cotton, thread density up to 95 yarns/cm and waterproofness corresponding to 500–750 mm water column hydrostatic pressure (Mukhopadhyay and Midha, 2008a, 2008b). Due to the vapour permeability given by its structural porosity (transversal pores), VENTILE can be considered the first textile breathablewaterproof material. Generally, conventional waterproofing treatments lead to the impossibility of fluids passing through textile materials due to the closing of the pores by covering them with a layer of polymer or a membrane (Ahn et al., 2010).
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Waterproof and Water Repellent Textiles and Clothing
Considering their morphological structure and/or their technology, waterproof materials can be classified as follows: 1. inherent waterproof materials; 2. textile materials with waterproofing finishing treatments (coated and laminated).
W.L. Gore’s expanded PTFE membrane is often regarded as the starting point of commercially available high performance waterproof breathable membranes. Initially an expanded PTFE membrane claiming 90% void volume was laminated to a support fabric, however, the pores became contaminated by sweat or detergents thus reducing the overall waterproofness (now used in windstopper fabrics). To overcome this drawback a thin hydrophilic polyurethane coating was applied to the body side of the membrane to prevent contamination (know as 2nd generation GoreTex).
1.3.3.1
Inherent waterproof materials
Inherent waterproof materials include materials with compact, nonporous structures that are completely impermeable to liquid or vapour water, namely: 1. polymeric foils; 2. textile materials laminated with polymeric foils.
Polymeric foils present a continuous compact and nonporous structure. With the development of plastics, polymeric foils became raw materials for weather protective garments, the so-called raincoats. Low density polyethylene (LDPE) and polyvinyl chloride (PVC) are the thermoplastic polymers most used for foils and films, the production technology requiring the planar extrusion of the melted polymers. Polymeric foils are suited for waterproof clothing due to their isotropic and compact structure, the low thickness (0.25–0.5 mm) and specific mass, the pieces being joined using adequate welding techniques. The use of PE and PVC foils presents the following major disadvantages: -
-
low mechanical strength, limiting the possibilities of using these waterproof materials to common applications, even if they exhibit good resistance to chemical or biological agents that recommend such materials for protective garments and high resistance to vapour transfer caused by the compact structure, generating discomfort due to the lack of ventilation within the microenvironment of the clothing system (overheating, perspiration at skin level, etc.).
The mechanical strength of the foils can be improved by laminating them to textile substrates (frequently nonwoven materials) extending their applications to technical and decorative textiles (Uludag et al., 2011).
1.3.3.2
Textile materials with waterproofing finishes
Waterproof materials are generally obtained using covering techniques that are considered surface finishing treatments. Covering is a general term referring to the placement on one or both sides of a textile material of one or more layers of adherent polymeric products that in the end form a film.
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There are two technologies for this type of material that have different ways for the application of the polymer: -
-
Coating technology, where the polymer is applied by direct layering and superficial impregnation, usually in the final stage of obtaining the waterproof material. The polymer can be applied as a paste or a high viscosity liquid. Such coatings are superthin, in the range of 10–100 μm. Laminating technology that involves in a first stage the formation of a laminating layer (membrane or foam) that is subsequently spread on the surface/surfaces of the textile material. The membrane is extremely thin (e.g. around 10 μm for PTFE) so the final thickness of the film remains also in the range of 10–100 μm.
Coated waterproof textiles Impregnation is a particular case where the polymer is deposited uniformly on the entire textile surface as a solution or a low- or high-viscosity dispersion using different processes that require the following technological phases: impregnation, drying and consolidation of the pellicle. A general characteristic of the impregnated materials is that the components cannot be clearly separated because the polymer is dispersed among the structural elements of the textile surface (see Fig. 1.4). The finishing technologies used cover either sides of the material (total impregnation) or just one side.
Laminated waterproof textiles The general characteristic of laminated materials is that the components are clearly delimited and in some cases they can even be detached (see Fig. 1.5). Such multicomponent products (two or more layers, one of which being the textile fabric) require bonding by the use of: -
a special adhesive added to the polymer (solutions in organic solvents, powders, granules, fibres) and the adhesive properties of one or more component layers (membranes, foams, expanded foils).
Fig. 1.4 Coated waterproof textile (SEM image 600) (Loghin, 1998).
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.5 Laminate waterproof textile (SEM image 600) (Loghin, 1998).
Natural or synthetic polymers are suitable for laminating textile materials. They present layering and adhesive characteristics, as well as properties determined by the application. Rubber is the only suitable natural polymer, while the range of synthetic polymers is much wider. An analysis of the consumption of synthetic polymers shows that 90% represent polyurethanes. Table 1.1 shows the most common polymers used for coating textile materials and the pellicle/film characteristics (Loghin, 2003). The morphological structure of the coated and laminated materials and the nature of the polymers are important from the garment manufacturing point of view, as they are key factors in obtaining a perfectly sealed waterproof product.
Table 1.1
Coating polymers used for waterproof textiles
No.
Polymers
Pellicle/film properties
Observations
1.
Synthetic rubbers
Are applied as dispersions or solutions in organic solvents, require vulcanization
2.
Polyolefins
3.
Polyvinyl chloride
- abrasion resistance - flexibility and elasticity - waterproofness - resistance to chemical agents - flexibility - waterproofness - resistance to frosting - resistance to chemical agents - stability to chemical agents - stability to light
Low pressure PE and PTFE are used, especially as compact membrane or foam
Is applied as solutions in solvents and thermoplastic films
Introduction to waterproof and water repellent textiles
Table 1.1
17
Continued
No.
Polymers
Pellicle/film properties
Observations
4.
Acrylic derivatives
Are applied as solutions/aqueous dispersions or solutions in organic solvents
5.
Polyurethanes
- stability to chemical agents - waterproofness - flexibility - elasticity - resistance to ageing - mechanical strength - resistance to ageing - elasticity - flexibility - waterproofness - noncreasing
Are applied as solutions in organic solvents or as foams
The morphological structure of these materials contains the components of the solid–gas ensemble that define the covering polymer and of the polymer-textile substrate system that characterizes the product at macroscopic level. When presenting the components, most authors recommend the macroscopic towards microscopic system. This way, the morphological structure includes: 1. The number of layers that make the coated or laminated waterproof material and their relative position in the garment. 2. The type of solid–gas system for the covering layer, meaning the absence or the presence of the pores (compact or porous layer) and the absence or the presence of other added substances. 3. The structure of the textile substrate; woven, knitted or nonwoven fabrics that can have different finishing treatments.
Considering their position in the garment, the coated or laminated waterproof materials can be: – With the covering layer towards the exterior; most representative are materials covered with elastomers and some materials laminated with compact foils. These materials have a high decontamination and/or cleaning capacity, being recommended for chemical protection and protection against particles. – With the covering layer towards the interior—especially used for wet weather protection. This variant is used for laminated materials (e.g. Gore-Tex) with a membrane or film with low mechanical strength. For increased durability, the polymeric film is covered with a hydrophilic polyurethane (PU) layer and/or a thin textile fabric (2.5L and 3L).
Based on the number of layers, there are: – materials with two layers (made of two layers, one of which is the textile substrate). The group includes most coated materials and 2L laminated materials. Fig. 1.6 illustrates graphically some structural variants for garments made of 2L laminated materials. The laminated
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Waterproof and Water Repellent Textiles and Clothing
1 2
a
3 1 2 4
b
3 1 c
2 3
Fig. 1.6 Structural variants of laminated materials. 1, outer fabric; 2, laminated polymer; 3, lining; and 4, support material (knitted or nonwoven fabric).
1 2 3
Fig. 1.7 Laminated material 3L. 1, textile fabric (exterior layer); 2, laminating polymer; and 3, lining.
structures can be used as outer materials (A), as an intermediary layer between the outer material and the lining (B) or as lining (C). The presented structural variants are typical for garments for weather protection for which the outer layer presents hydrophobic and/or oleophobic characteristics. – multilayer materials are made of at least 2.5 and 3 different layers, most representative being the sandwich 3L laminated materials (Fig. 1.7) used especially for protective clothing (protective equipment for fire fighters) and work clothing (industrial, police or military uniforms).
Another characterization of waterproof materials based on the solid–gas system of the covering layer refers to the presence or absence of the pores (compact or porous layer): – waterproof textiles with compact coating polymer (nonporous structure) applied as solution, dispersion (Fig. 1.8) or laminated with compact foils, that are in the same measure impermeable to water liquid and vapour water and – laminated textiles with microporous layers, considered to belong to the group of breathable materials, characterized by waterproofness and vapour permeability and used at large scale for manufacturing waterproof garments.
Ease of sealing and durability determine use of 2, 2.5 or 3 layer materials. The film is the weakest point
Introduction to waterproof and water repellent textiles
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Fig. 1.8 Compact coated waterproof textile (SEM image 600) (Loghin, 1998).
1.3.3.3 Breathable-waterproof textiles As mentioned before, the main problem in using waterproof textile materials for garment manufacturing is the need to ensure to a satisfactory degree the wearer’s comfort, as this function is affected by the decrease in ventilation in the clothing layers. Humidity absorption and transfer towards the external environment are determined by five physical mechanisms, as follow (Loghin and Ciobanu, 2008): – diffusion of the water vapour through the pores of the textile materials, determined by the partial pressure difference created between the outer and inner surface; – vapour adsorption and migration at fibre or yarn surface, determined by the surface tension generated in contact with water; – humidity adsorption and desorption in gas and/or liquid state in and from the fibres, generally with hysteresis that sometimes can lead to fibre swelling; – condensation followed by evaporation through free spaces, determined by simultaneously reaching the negativity condition for the difference in partial pressure, respectively temperature; and – convection from the internal microclimate (caused by the movement of the clothed human body) is mainly a phenomenon of thermal exchange, but it also involves the displacement of humid air through the fabric structure/layers. Garment endings (like cuffs, collar, bottom end) intensify the convection rate.
To produce coated and laminated waterproof-breathable textiles, the vapour transfer through the clothing layers towards the external environment is ensured by: 1. Materials with compact hydrophilic outer layer (Fig. 1.9). This layer is made of polymers with hydrophilic groups (dOH, dCOOH, dNH2, dCOOd, dCONH) (Loghin et al., 2009), in which case the vapours are eliminated through an absorption–desorption mechanism. An example is the SYMPATEX membrane (Akzo Nobel) made of a co-polyester obtained by grafting the polyester with polyether (Loghin et al., 2008). 2. Materials with porous outer layer, in which case the vapours are transferred by diffusion. This porous outer layer (hydrophilic PU film) is added to prevent the PTFE membrane becoming contaminated with different agents (oil, dirt, detergents, etc.). The hydrophilic PU layer insures the mechanical strength of the material.
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.9 Compact hydrophilic layer (SYMPATEX membrane) (Loghin, 1998).
To describe the different behaviour in relation to liquid water and vapours (the principle of membranes waterproof-breathable), there are certain considerations regarding the type, average diameter, form and distribution of the pores. Considering their type, the pores can be (i) individual; closed, partially closed or open (see Fig. 1.10); (ii) distributed in a net, communicating between them and with both sides of the membrane, this being the typical structure of materials coated with microporous PU. Considering the average diameter, the pores can be divided into (Colleoni et al., 2015): (i) macropores, with diameter over 50 nm and specific surface 0.5–2 m2 g1; (ii) mesopores, with diameter between 2 nm and 50 nm and specific surface 20–150 m2 g1; and (iii) micropores, with diameter under 2 nm (comparable to small molecules) and specific surface 400–900 m2 g1. The structures with pore dimensions less than 103 nm are considered microporous, while the ones with dimensions exceeding 103 nm are considered foams.
Fig. 1.10 Porous coating polymer (SEM image 600) (Loghin, 1998).
Introduction to waterproof and water repellent textiles
21
Environment Fog
Light rain
Rain
Downpour
100 µm 500 µm 2000 µm 3000 µm
25 µm 20 nm
Water vapor
0.1 nm
Body surface
Fig. 1.11 The principle of microporous membranes.
Fig. 1.11 presents the principle of microporous membranes (Loghin, 1998). Laminated and coated microporous materials have pores with much lower dimensions (2–50 nm) than the smallest rain drop (fog 100 μm), but bigger than the water molecules (0.1–10 nm) (Ahn et al., 2010). Taking into consideration the dimensions and density, the pore distribution can be uniform or nonuniform. Analysis of the porosity of the outer layer is determinant in evaluating the level to which the garment will respond to the requirements during use.
1.3.3.4 Multifunctional waterproof fabrics Recent developments in the field of multifunctional materials refer to waterproof textiles with multiple functions. Apart from common repellent finishes (often c8-fluorocarbon giving both oil and water repellency while maintaining high breathability), such materials require other specific treatments to create multifunctionality. The outer layers of the coated and laminated waterproof textiles can be produced as a matrix-dispersed phase composite, the additional substances enlarging the range of possible applications where multiple functionality is required: – Waterproof-breathable and electrostatic shielding. The multifunctional material is manufactured by coating or laminating a multilayer knitted fabric made of carbon core filaments and PES/stainless steel spun yarns with microporous PU. The resulting material is waterproof-breathable, and water and oil repellent, while ensuring electrostatic shielding (Varnaite-Zuravliova et al., 2016). The antistatic characteristics of the waterproof-breathable material are given by adding Ag nanoparticles in the polymer mass (Shyr et al., 2011). – Water repellent and flame retardant. Cellulosic materials used for tent manufacturing are covered with hexagonal boron nitrite nanosheets; this treatment creates hydrophobic (θ > 90 angle) and flame retardant characteristics (Yaras et al., 2016).
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Waterproof and Water Repellent Textiles and Clothing
– Waterproof-breathable and UV barrier, antimicrobial and antistatic properties. The anti-UV, antimicrobial and antistatic properties of the waterproof materials are obtained by adding to the polymer mass nanoparticles like nano-silver, TiO2, ZnO, SiO2, Al2O3 and UV blockers (Gowri et al., 2010). – Waterproof-breathable with enhanced vapour transfer properties obtained by laminating with layers of electrospun nanowebs. The resulting materials have waterproof characteristics similar to materials laminated with Polytetrafluorethylene (PTFE, GoreTex) but also improved vapour permeability, making these materials suited for outdoor clothing (Ahn et al., 2010).
1.3.3.5
Ecological issues regarding waterproof-breathable and water repellent fabrics
A significant issue is the recycling and environmental impact of these materials. Some of the polymers or finishing agents are not biodegradable, certain chemicals used are toxic, and the manufacturing processes are energy-intensive. There are materials that have components of a common nature (like SYMPATEX that has PES substrate and hydrophilic polyester membrane) and can be recycled simultaneously. In most cases, the components have different chemical structures and their recycling requires separation and selection. Extracting, collecting and/or removing chemical substances from the macrostructure of the waterproof and water repellent materials represents a great challenge for the future.
1.4
Conclusions
In a wet environment, the basic requirement for garments is to keep the wearer dry by being waterproof and/or water repellent. Waterproof and water repellent materials have a large range of applications, being widely used for garment manufacturing in conventional garments for weather protection, uniforms and work wear, and clothing for sport and leisure. In contact with water, water repellent materials form drops that can be easily removed from the fabric surface. A water repellent fabric is resistant to wetting by water droplets and to the spreading of water over its surface. The water repellency of a fabric prevents the water absorption into the macrostructure of the fabric, with good influence on garment weight and fabric breathability. Waterproof materials for clothing must also ensure the wearer’s comfort, presenting the capacity to transfer water vapour from the microclimate through the garment system. Waterproof-breathable materials coated or laminated with microporous polymers or hydrophilic membranes are commonly used for this basic function. The materials with a compact outer layer are used for technical applications, and home and outdoor textiles, because their design includes specific requirements such as mechanical strength, biodegradability, resistance to biological agents or low weight.
References Ahn, H.W., Park, C.H., Chung, S.E., 2010. Waterproof and breathable properties of nanoweb applied clothing. Text. Res. J. 81 (14), 1438–1447.
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Chinta, S.K., Satis, D., 2014. Studies in waterproof breathable textiles. Int. J. Rec. Dev. Eng. Technol. 3 (2), 16–20. Colleoni, C., Guido, E., Migani, V., Rosace, G., 2015. Hydrophobic behavior of non-fluorinated sol-gel based cotton and polyester fabric coatings. J. Ind. Text. 44 (6), 815–834. Gibson, P., 2008. Water-repellent treatment on military uniform fabrics: physiological and comfort implications. J. Ind. Text. 38 (1), 43–53. Gowri, S.S., Almeida, L., Amorim, T., et al., 2010. Polymer nanocomposites for multifunctional finishing of textiles: a review. Text. Res. J. 80 (13), 1290–1306. Grand View Research Inc., 2016. Waterproof Breathable Textiles Market Size, WBT Industry Report 2024, 250 pp., Report ID: 978-1-68038-316-4. Gugliuzza, A., Drioli, E., 2013. A review on membrane engineering for innovation in wearable fabrics and protective textiles. J. Membr. Sci. 446, 350–375. Holmes, D., 2000. Performance characteristics of waterproof breathable fabrics. J. Ind. Text. 29 (4), 306–316. Houtman, R., 2015. Materials used for architectural fabric structures. In: Llorens, J. (Ed.), Fabric Structures in Architecture. first ed. Woodhead Publishing Series in Textiles. ISBN: 9781782422402, pp. 101–121. Indu Shekar, R., Kasturiya, N., Raj, H., Mathur, G.N., 2001. Studies on effect of water repellent treatment on flame retardant properties of fabric. J. Ind. Text. 30 (3), 222–254. Kale, K.H., Palaskar, S., 2010. Atmospheric pressure plasma polymerization of hexamethyldisiloxane for imparting water repellency to cotton fabric. Text. Res. J. 81 (6), 608–620. Kaynak, H.K., Babaarslan, O., 2012. Polyester microfilament woven fabrics. In: Jeon, H.-Y. (Ed.), Woven Fabrics. InTech Publisher, ISBN: 978-953-51-0607-4, pp. 155–178. Kuhr, M., Aibibu, D., Cherif, C., 2016. Targeted partial finishing of barrier textiles with microparticles, and their effects on barrier properties and comfort. J. Ind. Text. 45 (5), 853–878. Loghin, C., 2003. Sudarea materialelor textile (Welding of Textile Materials). Performantica Publishing House, Iaşi, ISBN: 973-7994-35-3. Loghin, C., Ciobanu, L. (Eds.), 2008. Iˆmbra˘ca˘minte funcționala˘—Modelarea și simularea funcțiilor de protecție. PIM Publishing House, Iasi, ISBN: 978-606-520-128-6, pp. 45–60. Loghin, C., Nicolaiov, P., Ionescu, I., Hoblea, Z., 2009. Functional design of equipments for individual protection. In: Proceedings of International Conference Management of Technological Changes. 2, ISBN: 978-960-89832-8-1, pp. 693–696. Loghin, C., 1998. Cerceta˘ri privind aplicarea procedeelor neconvenționale de asamblare la realizarea subansamblelor și produselor vestimentare (Research on the application of unconventional assembly processes for garments producing). Ph.D. Thesis, “Gheorghe Asachi” Technical University of Iasi, Doctoral School. Lynch, A., Strauss, M.D. (Eds.), 2015. Ethnic Dress in the United Stated: A Cultural Encyclopedia. Rowman & Littlefield Publishing Group Inc, USA, ISBN: 978-0-7591-2148-5. Mukhopadhyay, A., Midha, V.K., 2008a. A review on designing the waterproof breathable fabrics. Part I. Fundamental principles and designing aspects of breathable fabrics. J. Ind. Text. 37 (3), 225–262. Mukhopadhyay, A., Midha, V.K., 2008b. A review on designing the waterproof breathable fabrics. Part II. Construction and suitability of breathable fabrics for different uses. J. Ind. Text. 38 (1), 17–40. Park, S., Kim, J., Park, C.H., 2016. Influence of micro and nano-scale roughness on hydrophobicity of a plasma-treated woven fabric. Text. Res. J. (00), 1–15. https://doi.org/ 10.1177/0040517515627169.
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Purane, S.V., Panigrahi, N.R., 2007. Microfibres, microfilaments & their applications. AUTEX Res. J. 7 (3), 148–158. Sen, A.K., 2008. Coated Textiles: Principles and Applications. CRC Press, Taylor & Francis, ISBN: 9781420053456. pp. 175–200. Schuyten, H.A., David Reid, J., Weaver, J.W., 1948. Imparting water-repellency to textiles by chemical methods—a review of the literature. Text. Res. J. 18 (7), 396–398. Shephard, A., 2012. Waterproof dress: patents as evidence of design and function from 1880 through 1895. Cloth. Text. Res. J. 30 (3), 183–199. Sherif, F., Roedel, H., 2011. Technical textiles as a new route to enhance orthopedic casts’ properties. Int. J. Cloth. Sci. Technol. 23 (1), 25–33. https://doi.org/ 10.1108/09556221111096714. Singha, K., 2012. A review on coating & lamination in textiles: processes and applications. Am. J. Polym. Sci. 2 (3), 39–49. https://doi.org/10.5923/j.ajps.20120203.04. Shyr, T.W., Lien, C.H., Lin, A.J., 2011. Coexisting antistatic and water-repellent properties of polyester fabric. Text. Res. J. 81 (3), 254–263. Uludag, M.O., Ozcan, G., Unal, H., 2011. Disposable hydrophilic antimicrobial laminated nonwoven bed sheet. Int. J. Cloth. Sci. Technol. 23 (4), 222–231. Varnaite-Zuravliova, S., Sankauskaite, A., Stygiene, L., et al., 2016. The investigation of barrier and comfort properties of multifunctional coated conductive knitted fabrics. J. Ind. Text. 45 (4), 585–610. Yaras, A., Er, E., et al., 2016. Cellulosic tent fabric coated with boron nitride nanosheets. J. Ind. Text. 45 (6), 1689–1700. Zerdzicki, K., 2015. Durability evaluation of textile hanging roofs materials. Mechanical engineering [physics.class-ph]. Ph.D. Thesis, Universite d’Orleans. Zimmermann, J., Seeger, S., Reifler, F.A., 2009. Water shedding angle: a new technique to evaluate the water-repellent properties of superhydrophobic surfaces. Text. Res. J. 79 (17), 1565–1570.
Further reading Global Market Insights, 2012. Waterproof breathable textiles market, https://www.gminsights. com/pressrelease/waterproof-breathable-textiles-wbt-market. Hes, L., Loghin, C., 2009. Heat, moisture and air transfer properties of selected woven fabrics in wet state. J. Fiber Bioeng. Inform. 2 (3), 141–149. Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh. Asachi Publishing House, Iasi, ISBN: 973-99209-4-2, pp. 50–60. Lee, K., Cho, G., 2014. The optimum coating condition by response surface methodology for maximizing vapor-permeable water resistance and minimizing frictional sound of combat uniform fabric. Text. Res. J. 84 (7), 684–693. Loghin, C., 2013. Some aspects regarding the radio frequency welding of textile composites, bulletin of the polytechnic institute. Mech. Eng. 59 (1), 125–133. Loghin, C., Ursache, M., Mureșan, R., Mureșan, A., 2010. Surface treatments applied to textile materials and implications on their behaviour in wet conditions. Ind. Textila˘ 61 (6), 284–290.
1
Carmen Loghin, Lumința Ciobanu, Dorin Ionesi, Emil Loghin, Irina Cristian “Gheorghe Asachi” Technical University of Ias¸i, Ias¸i, Romania
1.1
Introduction
Protection against environmental factors is the initial function of clothing. In a wet environment, the basic requirement for garments is to keep the wearer dry by being waterproof and or water repellent. The difference between the two terms is essential when characterizing the behaviour of textile materials in reference to liquid water. In contact with water, water repellent materials form drops that can be easily removed from the fabric surface but for longer contact with water or with a higher pressure difference, the material will absorb water. Water repellent textiles are often high density woven materials made of very fine yarns or common materials with hydrophobic surface treatment. Waterproofing is defined as the property of a material not to be penetrated by fluids. The waterproofness of a fabric can be measured using two testing methods: one that simulates raining and the other (more common) that subjects the fabric to hydrostatic pressure. The minimum value for the hydrostatic pressure without leaking at its surface, at which a fabric is considered rainproof is 5000 mm water column, while for waterproof materials the hydrostatic pressure can reach 10,000–15,000 mm water column (Loghin, 2003). For high quality waterproof materials designed for aggressive conditions, the hydrostatic pressure varies between 15,000 and 30,000 mm water column. Such fabrics are completely waterproof even under very high pressure. First historical mentions regarding the hydrophobization of textiles are in the 15th century, when sailors tried to obtain sea water protective clothing by impregnating it with linseed oil, animal fat or wax. The first bio-inspired waterproof clothing product (kamleika) belongs to Aleut American Indians who used dried seal or whale intestines; the seams have been sealed with animal glues to make the product totally waterproof (Lynch and Strauss, 2015). The first waterproof fabric was produced and patented by Charles Macintosh in 1823 in England (Shephard, 2012). The process to produce waterproof materials involves the spreading of a rubber layer between two woven fabrics. The problems related to the use of garments made of this material, caused by the unstable rubber, were eliminated by the process of rubber vulcanization that led to a textile material more stable in environmental conditions. The process was patented in 1844 by Charles Goodyear in the United States, and Thomas Hancock in England. For a long period, rubberized textile fabrics were the raw material for waterproof garments. The main problem with these garments is reduced comfort due to the Waterproof and Water Repellent Textiles and Clothing. https://doi.org/10.1016/B978-0-08-101212-3.00001-0 Copyright © 2018 Elsevier Ltd. All rights reserved.
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overheating of the wearer’s body and high resistance to vapour passing out through the clothing layers. The sweat vapours condense in contact with the interior surface of the clothing, humidifying the textile layers in direct contact with the skin and causing increased discomfort. Subsequent researches conducted in the production of waterproof textiles led to a new type of material, waterproof-breathable fabrics. Ventile fabrics are waterproof, breathable, densely woven materials developed in the UK during WWII to replace flax in garments for outdoor, military, medical and work wear applications. The first microporous membrane (polytetrafluoroethylene PTFE, also known as Teflon) was created in 1969 by W. L. Gore and Associates. The first GORE-TEX materials appeared on the market in 1976, starting a revolution in the concept of waterproof-breathable garments. Water repellent textiles are obtained using specific finishing surface treatments. A review by Schuyten et al. (1948) shows that these hydrophobic treatments were developed significantly starting with 1920s. Waterproof-breathable textiles represent a significant global market, with major players from the US, Europe and Asia. A press release for a report from Grand View Research Inc. (2016) indicates the value of the waterproof breathable textiles market in 2014 was $1.43 billion. Membrane waterproof-breathable products account for 71% of the overall demand, while garments remain the main application. The report anticipates a constant growth of this market, stimulated by the need for comfortable multifunctional products, the use of innovative technologies to produce biomimetic and smart textiles, and the focus on recyclable and eco-friendly products. With an estimated compound annual growth rate (CAGR) over 5% per annum, the market of waterproof-breathable textiles is expected to reach $2.18 billion by 2020.
1.2
Areas of application of waterproof and water repellent textiles
Waterproof and water repellent materials are currently used in the three major textile areas (clothing, home and outdoor products and technical textiles). There are a large number of possible applications, from rain garments to medical and military equipment (Singha, 2012). Regardless of the applications for which waterproofness is the determinant function, the complexity of the conditions during use requires the multicriterial design of the fabric structure and its testing to ensure a high number of functional characteristics such as: vapour permeability, tensile strength, abrasion resistance, flexural strength (repeated cycles), resistance to low and high temperatures, resistance to light, chemical resistance and more. Several standards are used for the evaluation of waterproof-breathable and water repellent textiles. Waterproofness is measured as the hydrostatic pressure needed to penetrate the waterproof-breathable fabrics. The standards used for determining waterproofness are: – ASTM D 3393-91 Standard Specification for Coated Fabrics—Waterproofness. – AATCC TM 127-water resistance: hydrostatic pressure test.
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– ISO 811 Textile fabrics—Determination of resistance to water penetration—Hydrostatic pressure test. – BS 3424-26 Testing coated fabrics. Methods 29A, 29B, 29C and 29D. Methods for determination of resistance to water penetration and surface wetting.
Breathability is evaluated based on water vapour transmission (WVT). There are several test methods, applicable to both coated and laminated fabrics: (1) The upright cup test—JIS L 1099, JIS Z 0208, ISO 2528, Desiccant Method of ASTM E96, JIS K 6328. (2) The inverted cup method—JIS L 1099, similar to ASTM E96-BW test method. (3) The sweating hot plate method (evaporative resistance)—ISO 11092, ASTM F 1868. (4) The dynamic moisture permeation cell—ASTM F 2298.
Water repellency is tested using the following standards: – – – –
AATCC TM 22-water repellency: spray test. ISO 9865-water repellency: Bundesmann rain shower test. AATCC TM 35-water resistance: rain test. ISO 22958:2005 Textiles—Water resistance—Rain tests: exposure to a horizontal water spray. – EN 14360-rain test (test method for ready-made garments). – AATCC TM 42-water resistance: impact penetration test.
1.2.1
Clothing design specifics according to the end use
Garments remain the most frequent use of waterproof and/or water repellent fabrics. Due to the complex requirements of the users (protection, comfort, aesthetic, identity, etc.), waterproof materials must have a sum of properties that ensure the multifunctional characteristics of the garment. The level of performance of the waterproof and water repellent materials used for garments is determined by two groups of factors: (i) subjective variables, defined by the requirements and the level of comfort of the final user and (ii) objective variables, defined by the environmental conditions, risk factors and specifics of the activities carried out by the user. A first level of classification for waterproof clothing contains: – – – –
conventional wet-weather clothing; work clothing and uniforms (including military); clothing for sport and leisure; and personal protective equipment (PPEs) (for risk conditions).
The main problem when using waterproof fabrics for garments is the comfort of the wearer. Usually, waterproof technologies consisted in covering and blocking the pores of the textile substrate so water absorption and transfer from the exterior towards the body are no longer possible. This way, the material acts like a barrier for the humidity in the environment, apparently satisfying the protection function of the garment. In the relationship between the human body, the garment and environment, the transfer of humidity must be analysed in both directions from and towards the body. Human skin sweats continuously, both at rest (insensible perspiration or perspiratio insensibilis),
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Waterproof and Water Repellent Textiles and Clothing
or in activity (sensible perspiration). For example, during intense effort the average human body (with a 1.8 m2 skin surface) produces approx. 1000 cm3 perspiration per hour to reach its thermal balance (Holmes, 2000). The humidity produced through perspiration must be eliminated as vapour in a process of mass transfer through the layers of the garment. This problem was solved in the 1980s by the production of waterproof-breathable textiles, which are materials waterproof for liquid water in the environment but permeable to sweat vapours from the body passing through clothing layers (Section 1.3.3.3).
1.2.1.1
Conventional wet-weather clothing
Conventional garments are used in wet environments (rain and snow) and their waterproofness is determined by special characteristics of the materials. The basic material can be water repellent for short periods of rain or snow, or waterproof and water repellent for long exposures to rain or snow. This type of garment includes: – waterproof garments (raincoats, jackets, trousers); – waterproof garments with high thermal insulating characteristics and low weight (e.g. equipment for winter sports); – waterproof bioactive garments (insect repellent, antiallergic, antibacterial) to be used in outdoor activities in insect-infested environments, and in medical applications where the risk for infections is very high; – waterproof UV garments for outdoor sports (fishing, camping, hiking, etc.), as well as work wear for workers exposed to UV; and – low maintenance products with increased cleaning characteristics (e.g. work wear, clothing for children, etc.).
Work clothing, including uniforms, can be considered conventional waterproof garments, used in similar conditions but only in the working period. The fundamental aspects that have to be taken into consideration when designing a waterproof garment and subsequently the selection criteria (Loghin and Ciobanu, 2008; Mukhopadhyay and Midha, 2008a; Chinta and Satis, 2014) are: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
waterproofness level; fabric weight; level of thermal physiological comfort; the capacity to allow the transfer of sweat vapour; aesthetics; durability (strength to repeated flexural cycles, tear, tensile, friction strength); launderability (washing/dry cleaning/tumble drying); resistance of the water repellent treatment to repeated laundering and cleaning; visibility (for work wear); identification/identity (for uniforms); and flame retardant (for work wear and uniforms), etc.
Waterproofness and air (wind) resistance/proofness of the materials are the most important issues in the case of weather protective outer garments. For such garments, water/airproofness must be considered at constructive, structural and technological levels, as illustrated in Fig. 1.1.
Simplified geometry of the patterns Reducing the section lines of the basic elements (front, back, sleeves)
Constructive Number of elements
Increasing the number of functional elements used for: • Bottom lines • Sectioning of the main eolements and their partial replacement with nets • Closure systems • Pockets
Membranes Raw materials
Water repellent finishing Multicomponent (sandwich) structures
Special finishing
Structural, depending on
Waterproofing Secondary raw materials
Coated with polymers
Simplified technological structure of the garment elements
Technological
Introduction to waterproof and water repellent textiles
Particularities
Textile aspect (the textile material is visible on the front) Coated or laminated
Welding or bonding
Compact aspect (the textile material act as support)
Joining methods Mixt (sewing-welding or sewing bonding)
Fig. 1.1 Design characteristics for waterproof clothing. 7
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Waterproof and Water Repellent Textiles and Clothing
Designing a waterproof garment requires certain constructive solutions (geometrical pieces, few cut lines, most sealed constructive variants for closures and/or pockets) and technological processing (welding or bonding/ sealing, sewing and welding, sewing and sealing). Replacing sewing with welding technologies or the use of seam sealing are decisions essential for the garment quality, because the holes produced by the needles during sewing lead to diminished waterproofness.
1.2.1.2
Sport and leisure garments
The requirements for sport and leisure garments are similar to the ones for conventional clothing, but the functional performance level of the waterproof materials needs to be higher due to increased sweating in intense effort, requiring a higher moisture transfer rate from the body towards the exterior. For example, for an effort rate of 500 watts, the perspiration rate is approximately 800 g/hour (Mukhopadhyay and Midha, 2008b). The main part of this humidity transfers through the garment, the rest representing losses through ventilation and respiration. The results of athletes are often influenced decisively by the performance level of the clothing. The potential of waterproof and/or water repellent materials to be used for multifunctional sport garments is illustrated in the examples below: – – – –
waterproof garments for winter sports; self-ventilating waterproof garments; waterproof garments with moisture control; and antimicrobial and antifungal waterproof garments.
The basic requirements for waterproof sportswear and leisurewear are as follows, ranked in this order: 1. good heat and mass transfer capacity; 2. good vapour permeability in relation to air proofness; and 3. moisture control, assured by: humidity absorption and its transport towards the exterior (environment); keeping the skin dry; and quick drying after humidity absorption; 4. good dimensional stability in wet state; 5. aesthetic aspect; 6. low weight; 7. pleasant touch; 8. low maintenance; and 9. durability, etc.
1.2.1.3
Personal protective equipment
PPE represent a set of individual protective means (clothing, footwear, head protection, gloves, masks, etc.). Protective clothing must ensure complete or almost complete insulation from the environmental factors (weather, hazards), some of these factors are harmful to human health. In the conditions of hazardous environments, waterproofness is a major requirement that most of the time must be correlated with
Introduction to waterproof and water repellent textiles
9
other requirements for the protective garment in specific working conditions. The complex protection requirements for the working and protective equipment and/or working environment can be as follows: 1. For work that involves fluid flow: the possibility for self starting or self blocking, spill, immersion-waterproof fabric, seam sealing, resistance to dynamic loads. 2. For work that involves microbiological cultures, bacteria, physiological fluids: impervious fabric, seam sealing, mechanical strength, decontamination capacity. 3. Outdoor work environment with low temperatures: thermal insulation, waterproof fabric, seam sealing. 4. Work environments with high humidity, precipitations, air currents: waterproof fabric, seam sealing. 5. Work environments with dangerous powders or suspensions of microorganisms: impervious fabric, seam sealing, decontamination capacity. 6. Gaseous work environment, toxic vapours, aerosols: impervious fabric, seam sealing, specific chemical resistance. 7. Gaseous work environment, inflammable vapours or explosives: impervious fabric, seam sealing, specific chemical resistance, antistatic properties, flame retardant characteristics. 8. Sterile work environment, clean rooms: impervious fabric, seam sealing, antistatic properties.
In the case of conventional clothing, waterproofness is perceived as the property of the materials to oppose the passing of air and water and therefore a measure of protection against atmospheric factors while ensuring the wearer’s comfort. It therefore needs to be breathable, not impermeable. In the case of protective clothing, waterproofness (imperviousness or impermeability) has many aspects, depending on the system of factors and leading to a specialization of the waterproof materials. The following types of impervious textiles can be listed: – – – – –
impervious to impervious to impervious to impervious to impervious to
1.2.2
water/air and permeable to water vapours; chemical agents; biological agents (microorganisms, physiological fluids); radioactive contaminants; and micro-particles generated by the human body, e.g. for clean rooms.
Home and outdoor textiles
Waterproof and water repellent textiles become more and more common in products used at home, as well as for the outside. For home textiles, main applications are pillow protectors, bed covers, bed sheets and mattress covers. Shower curtains can also be made from waterproof textile materials. Decorative mobile walls can also be made from this type of material. If needed, further treatments can be applied to the textile-coated materials, like antifungal, antidust mites and antibacterial, halogen-free fire retardant treatments (Sen, 2008). Home outdoor applications include small shade structures and other decorative outside elements, covers for chairs and tables in the garden, etc. Apart from clothing
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Waterproof and Water Repellent Textiles and Clothing
for outdoor activities, waterproof/water repellent materials are also used for specific equipment such as tents, backpacks, hiking gear, insect repellent curtains, etc.
1.2.3
Technical applications
There is a wide range of technical/functional applications that use waterproof or water repellent textiles including agricultural, civil engineering, medical, industrial and packing applications. In agriculture, waterproof-breathable textiles are used for different cultures (breathable ground cover for weed control, waterproof sheeting, root protective bags for transporting, greenhouse covers, tree shelters), as well as structures with agricultural use (leak-proof sheeting for water and liquid fertilizer tanks and flexible water tanks) and packing for product transport. Architectural textiles are lightweight, flexible materials that can be used for temporary and permanent structures. Waterproof coated or impregnated textiles can save energy and decrease costs, while allowing for innovative creative approaches to architecture. Water repellent treatments are also applied to such materials, especially for outdoor applications, to improve their behaviour in wet weather. Temporary applications using textile membranes (woven fabrics with PVC) include tents, clear-span structures, tension fabric structures and air structures and commonly built for exhibition spaces, structure for leisure activities, short-term commercial spaces, social gatherings, storage facilities, etc. Such materials are high strength woven fabrics made of glass, fibres, PES or polyethylene coated with PVC, silicone, PTFE ref (Houtman, 2015). Textile membranes are suitable for roofs due to their lower weight, controlled mechanical strength including impact, resistance to weather, controlled translucence, sound insulation capacity, fire retardant characteristics and resistance to UV (Zerdzicki, 2015). To increase their behaviour, a hydrophobic top coating can be added to the materials, while titanium dioxide (TiO2) photo-catalyst provide self-cleaning properties. Another advantage is that textile membrane roofs can be fixed or retractable. Another domain of application refers to decorative waterproof textiles like canopies, awnings, marquees, shading structures and advertising structures that are placed on buildings or are in the immediate public space. Waterproof textiles are widely used in medical applications, for nonimplantable and healthcare and hygiene products. Literature presents examples of waterproof breathable textiles (woven, knitted) used for orthopaedic orthoses to improve the level of comfort for patients, replacing the neoprene commonly used. Another orthopedic end-use is a knitted breathable cast for upper or lower limbs (Sherif and Roedel, 2011). Modern multilayer wound dressings have an outer layer (mostly nonwoven) that is waterproof-breathable. Healthcare products include wheelchair cushions, mattress covers, pillow protectors, bed-stretchers, stretchers and hospital cases. Another application is for surgical gowns and drapes. Apart from their characteristics, these products must also ensure a clean environment around the patients and medical staff, so the coating must include antifungal and antibacterial substances. The coating can also be designed to ensure viral protection, an important issue in hospitals.
Introduction to waterproof and water repellent textiles
1.3
11
Basic aspects regarding waterproof and water repellent textiles
1.3.1
Textile and water interaction mechanism
Because waterproofness is a requirement imposed mainly by the environment (weather conditions), the behaviour of textile materials towards liquid water must be commented upon. From this point of view, textile materials can be divided into: 1. materials with water absorption and retaining characteristics—hydrophilic materials; 2. materials that repel water—hydrophobic materials.
The capacity of the textile surface to absorb or repel liquid water is explained through the surface tension developed at the interface between the water drop and textile surface (see Fig. 1.2). The surface tension γ 12 generated at the interface depends on the fibrous composition of the textile material, the structural parameters of the yarn and material and the microstructure of the contact area (smooth, micro rough, continuous, discontinuous, etc.) (Park et al., 2016). Another factor influencing the balance of the superficial tensions is the material’s porosity, namely the state of the transversal pores after water repellent finishes (open, blocked uni- or bilaterally). Fig. 1.3 presents the simplified structure of a textile material, emphasizing the transversal (PT), longitudinal (PL) and superficial (PS) pores. The behaviour of a textile material towards liquid water is evaluated based on the value of the contact angle (θ), with the following formula (Young’s Equation): cos θ ¼
γ 13 λ12 γ 23
(1.1)
where γ 12, γ 13 and γ 23 represents the surface (interfacial) tensions of the fabric-water (γ 12), fabric-air (γ 13), and water-air (γ 23) contact. Theoretically, the value of the contact angle is placed in the interval 0 angle and 180 angle. The textile materials can be classified accordingly into (Gugliuzza and Drioli, 2013; Zimmermann et al., 2009): g23
g13
Air (3)
q
Water (2) g12 Fabric (1)
Fig. 1.2 Surface tensions at the contact between the fabric and the water drop theoretical model. From Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh.Asachi Publishing House, Iasi, pp. 50–60, ISBN 973-99209-4-2. Published with the author’s permission.
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.3 The porous structure of a textile surface (simplified model). From Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh.Asachi Publishing House, Iasi, pp. 50–60, ISBN 973-99209-4-2. Published with the author’s permission. -
superhydrophilic materials, θ ! 0 angle; hydrophilic materials (including textiles), 0 angle < θ < 90 angle; hydrophobic materials (including textiles), 90 angle θ < 150 angle; superhydrophobic materials (including textiles), 150 angle θ 180 angle.
1.3.2
Water repellent textiles
Hydrophobic textiles present the advantage of air permeability but offer less protection against water, being generally used for conventional garments or as an exterior layer for waterproof clothing. Based on the resistance to cleaning agents, the hydrophobicity can be permanent (durable water repellent, DWR) or temporary (Gibson, 2008). Depending on the way the water repellent effect is obtained, there are two groups of textile materials: 1. inherent water repellent textile materials; 2. textile materials with water repellent finishing.
Water repellent characteristics are specific to compact textile structures. Inherent water repellent materials are (i) high density woven fabrics, made of very fine yarns and filaments and (ii) nonwoven materials. Microfibres and microfilaments present a high technological potential, with a practically unlimited area of applications (garments, household, medical and technical textiles) due to their special surface properties. In this group are included fibres with fineness 0.3–1 dtex, with the interval 0.3–0.1 dtex for super-microfibres. These fibres are made of synthetic polymers—PTE, PA, PP, PAN or cellulose (Purane and Panigrahi, 2007). The specific properties and implicitly the end-use are determined by the morphological structure of the microfibres and their specific technology. The properties of the woven fabrics controlled through the particular characteristics of the microfibres refer to:
Introduction to waterproof and water repellent textiles
-
-
-
13
water repellency and air impermeability due to the high density of the fabrics made of microfilaments (e.g. a fabric made of 0.2 dtex microfilaments has a thread density of 7000 microfilaments/cm2) (Kaynak and Babaarslan, 2012); the vapour permeability varies in acceptable limits due to the interstitial porosity of the textile surface; increased filtering/absorption capacity of solid particles in reference to other fibres determined by the significantly higher specific surface, given by the number of microfibres per unit area and the cross section geometry (segmented, cross or island type structure); and increased liquid absorption capacity concurrent with an increased drying rate due to the same bigger specific surface, intensifying the capillary activities at textile surface level.
The hydrophobization of the textile materials is carried out with different chemicals that ensure high superficial tension in relation to water. These substances orient their hydrophobic groups towards the textile fibres thus forming a protective brush against water. The water hydrophobization agent forces are null, facilitating the water drop to maintain its spherical shape without spreading onto the fibres. In general, the limitations of the water repellent treatments refer to low surface energy and extended surface porosity. The technological variants for hydrophobization include: 1. Hydrophobization with additives (aluminium organic salts, aluminium soaps, paraffin emulsions with aluminium salts). 2. Hydrophobization with resin type reactive agents (perfluoro ester-aziridine , zirconium compounds, radical crosslinking of methyl or cyanoethyl silicones (Indu Shekar et al., 2001) fluorocarbon (FC) resin (Kuhr et al., 2016)). 3. Hydrophobization through chemical modification of the fibres (esterification or etherification reactions). 4. Textile finishing with nanoparticles that create an ultrahydrophobic surface with selfcleaning characteristics (lotus effect). Oleophobization techniques give textile materials the property of repelling oils and thus creating a protection against dirt and smudges, while increasing the hydrophobization effect. FC resins are used as oleophobization agents—water emulsions or solutions in solvents (Kuhr et al., 2016). 5. Plasma treatment of the textile materials (Colleoni et al., 2015), plasma polymerization or plasma depositing of organic-silicone polymers (Kale and Palaskar, 2010) can give a hydrophobic character to materials that are typically not hydrophobic, like 100% cotton.
1.3.3
Waterproof textiles
An initial example of this type of materials is the high-density woven fabric VENTILE, made of 100% cotton, thread density up to 95 yarns/cm and waterproofness corresponding to 500–750 mm water column hydrostatic pressure (Mukhopadhyay and Midha, 2008a, 2008b). Due to the vapour permeability given by its structural porosity (transversal pores), VENTILE can be considered the first textile breathablewaterproof material. Generally, conventional waterproofing treatments lead to the impossibility of fluids passing through textile materials due to the closing of the pores by covering them with a layer of polymer or a membrane (Ahn et al., 2010).
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Waterproof and Water Repellent Textiles and Clothing
Considering their morphological structure and/or their technology, waterproof materials can be classified as follows: 1. inherent waterproof materials; 2. textile materials with waterproofing finishing treatments (coated and laminated).
W.L. Gore’s expanded PTFE membrane is often regarded as the starting point of commercially available high performance waterproof breathable membranes. Initially an expanded PTFE membrane claiming 90% void volume was laminated to a support fabric, however, the pores became contaminated by sweat or detergents thus reducing the overall waterproofness (now used in windstopper fabrics). To overcome this drawback a thin hydrophilic polyurethane coating was applied to the body side of the membrane to prevent contamination (know as 2nd generation GoreTex).
1.3.3.1
Inherent waterproof materials
Inherent waterproof materials include materials with compact, nonporous structures that are completely impermeable to liquid or vapour water, namely: 1. polymeric foils; 2. textile materials laminated with polymeric foils.
Polymeric foils present a continuous compact and nonporous structure. With the development of plastics, polymeric foils became raw materials for weather protective garments, the so-called raincoats. Low density polyethylene (LDPE) and polyvinyl chloride (PVC) are the thermoplastic polymers most used for foils and films, the production technology requiring the planar extrusion of the melted polymers. Polymeric foils are suited for waterproof clothing due to their isotropic and compact structure, the low thickness (0.25–0.5 mm) and specific mass, the pieces being joined using adequate welding techniques. The use of PE and PVC foils presents the following major disadvantages: -
-
low mechanical strength, limiting the possibilities of using these waterproof materials to common applications, even if they exhibit good resistance to chemical or biological agents that recommend such materials for protective garments and high resistance to vapour transfer caused by the compact structure, generating discomfort due to the lack of ventilation within the microenvironment of the clothing system (overheating, perspiration at skin level, etc.).
The mechanical strength of the foils can be improved by laminating them to textile substrates (frequently nonwoven materials) extending their applications to technical and decorative textiles (Uludag et al., 2011).
1.3.3.2
Textile materials with waterproofing finishes
Waterproof materials are generally obtained using covering techniques that are considered surface finishing treatments. Covering is a general term referring to the placement on one or both sides of a textile material of one or more layers of adherent polymeric products that in the end form a film.
Introduction to waterproof and water repellent textiles
15
There are two technologies for this type of material that have different ways for the application of the polymer: -
-
Coating technology, where the polymer is applied by direct layering and superficial impregnation, usually in the final stage of obtaining the waterproof material. The polymer can be applied as a paste or a high viscosity liquid. Such coatings are superthin, in the range of 10–100 μm. Laminating technology that involves in a first stage the formation of a laminating layer (membrane or foam) that is subsequently spread on the surface/surfaces of the textile material. The membrane is extremely thin (e.g. around 10 μm for PTFE) so the final thickness of the film remains also in the range of 10–100 μm.
Coated waterproof textiles Impregnation is a particular case where the polymer is deposited uniformly on the entire textile surface as a solution or a low- or high-viscosity dispersion using different processes that require the following technological phases: impregnation, drying and consolidation of the pellicle. A general characteristic of the impregnated materials is that the components cannot be clearly separated because the polymer is dispersed among the structural elements of the textile surface (see Fig. 1.4). The finishing technologies used cover either sides of the material (total impregnation) or just one side.
Laminated waterproof textiles The general characteristic of laminated materials is that the components are clearly delimited and in some cases they can even be detached (see Fig. 1.5). Such multicomponent products (two or more layers, one of which being the textile fabric) require bonding by the use of: -
a special adhesive added to the polymer (solutions in organic solvents, powders, granules, fibres) and the adhesive properties of one or more component layers (membranes, foams, expanded foils).
Fig. 1.4 Coated waterproof textile (SEM image 600) (Loghin, 1998).
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.5 Laminate waterproof textile (SEM image 600) (Loghin, 1998).
Natural or synthetic polymers are suitable for laminating textile materials. They present layering and adhesive characteristics, as well as properties determined by the application. Rubber is the only suitable natural polymer, while the range of synthetic polymers is much wider. An analysis of the consumption of synthetic polymers shows that 90% represent polyurethanes. Table 1.1 shows the most common polymers used for coating textile materials and the pellicle/film characteristics (Loghin, 2003). The morphological structure of the coated and laminated materials and the nature of the polymers are important from the garment manufacturing point of view, as they are key factors in obtaining a perfectly sealed waterproof product.
Table 1.1
Coating polymers used for waterproof textiles
No.
Polymers
Pellicle/film properties
Observations
1.
Synthetic rubbers
Are applied as dispersions or solutions in organic solvents, require vulcanization
2.
Polyolefins
3.
Polyvinyl chloride
- abrasion resistance - flexibility and elasticity - waterproofness - resistance to chemical agents - flexibility - waterproofness - resistance to frosting - resistance to chemical agents - stability to chemical agents - stability to light
Low pressure PE and PTFE are used, especially as compact membrane or foam
Is applied as solutions in solvents and thermoplastic films
Introduction to waterproof and water repellent textiles
Table 1.1
17
Continued
No.
Polymers
Pellicle/film properties
Observations
4.
Acrylic derivatives
Are applied as solutions/aqueous dispersions or solutions in organic solvents
5.
Polyurethanes
- stability to chemical agents - waterproofness - flexibility - elasticity - resistance to ageing - mechanical strength - resistance to ageing - elasticity - flexibility - waterproofness - noncreasing
Are applied as solutions in organic solvents or as foams
The morphological structure of these materials contains the components of the solid–gas ensemble that define the covering polymer and of the polymer-textile substrate system that characterizes the product at macroscopic level. When presenting the components, most authors recommend the macroscopic towards microscopic system. This way, the morphological structure includes: 1. The number of layers that make the coated or laminated waterproof material and their relative position in the garment. 2. The type of solid–gas system for the covering layer, meaning the absence or the presence of the pores (compact or porous layer) and the absence or the presence of other added substances. 3. The structure of the textile substrate; woven, knitted or nonwoven fabrics that can have different finishing treatments.
Considering their position in the garment, the coated or laminated waterproof materials can be: – With the covering layer towards the exterior; most representative are materials covered with elastomers and some materials laminated with compact foils. These materials have a high decontamination and/or cleaning capacity, being recommended for chemical protection and protection against particles. – With the covering layer towards the interior—especially used for wet weather protection. This variant is used for laminated materials (e.g. Gore-Tex) with a membrane or film with low mechanical strength. For increased durability, the polymeric film is covered with a hydrophilic polyurethane (PU) layer and/or a thin textile fabric (2.5L and 3L).
Based on the number of layers, there are: – materials with two layers (made of two layers, one of which is the textile substrate). The group includes most coated materials and 2L laminated materials. Fig. 1.6 illustrates graphically some structural variants for garments made of 2L laminated materials. The laminated
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Waterproof and Water Repellent Textiles and Clothing
1 2
a
3 1 2 4
b
3 1 c
2 3
Fig. 1.6 Structural variants of laminated materials. 1, outer fabric; 2, laminated polymer; 3, lining; and 4, support material (knitted or nonwoven fabric).
1 2 3
Fig. 1.7 Laminated material 3L. 1, textile fabric (exterior layer); 2, laminating polymer; and 3, lining.
structures can be used as outer materials (A), as an intermediary layer between the outer material and the lining (B) or as lining (C). The presented structural variants are typical for garments for weather protection for which the outer layer presents hydrophobic and/or oleophobic characteristics. – multilayer materials are made of at least 2.5 and 3 different layers, most representative being the sandwich 3L laminated materials (Fig. 1.7) used especially for protective clothing (protective equipment for fire fighters) and work clothing (industrial, police or military uniforms).
Another characterization of waterproof materials based on the solid–gas system of the covering layer refers to the presence or absence of the pores (compact or porous layer): – waterproof textiles with compact coating polymer (nonporous structure) applied as solution, dispersion (Fig. 1.8) or laminated with compact foils, that are in the same measure impermeable to water liquid and vapour water and – laminated textiles with microporous layers, considered to belong to the group of breathable materials, characterized by waterproofness and vapour permeability and used at large scale for manufacturing waterproof garments.
Ease of sealing and durability determine use of 2, 2.5 or 3 layer materials. The film is the weakest point
Introduction to waterproof and water repellent textiles
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Fig. 1.8 Compact coated waterproof textile (SEM image 600) (Loghin, 1998).
1.3.3.3 Breathable-waterproof textiles As mentioned before, the main problem in using waterproof textile materials for garment manufacturing is the need to ensure to a satisfactory degree the wearer’s comfort, as this function is affected by the decrease in ventilation in the clothing layers. Humidity absorption and transfer towards the external environment are determined by five physical mechanisms, as follow (Loghin and Ciobanu, 2008): – diffusion of the water vapour through the pores of the textile materials, determined by the partial pressure difference created between the outer and inner surface; – vapour adsorption and migration at fibre or yarn surface, determined by the surface tension generated in contact with water; – humidity adsorption and desorption in gas and/or liquid state in and from the fibres, generally with hysteresis that sometimes can lead to fibre swelling; – condensation followed by evaporation through free spaces, determined by simultaneously reaching the negativity condition for the difference in partial pressure, respectively temperature; and – convection from the internal microclimate (caused by the movement of the clothed human body) is mainly a phenomenon of thermal exchange, but it also involves the displacement of humid air through the fabric structure/layers. Garment endings (like cuffs, collar, bottom end) intensify the convection rate.
To produce coated and laminated waterproof-breathable textiles, the vapour transfer through the clothing layers towards the external environment is ensured by: 1. Materials with compact hydrophilic outer layer (Fig. 1.9). This layer is made of polymers with hydrophilic groups (dOH, dCOOH, dNH2, dCOOd, dCONH) (Loghin et al., 2009), in which case the vapours are eliminated through an absorption–desorption mechanism. An example is the SYMPATEX membrane (Akzo Nobel) made of a co-polyester obtained by grafting the polyester with polyether (Loghin et al., 2008). 2. Materials with porous outer layer, in which case the vapours are transferred by diffusion. This porous outer layer (hydrophilic PU film) is added to prevent the PTFE membrane becoming contaminated with different agents (oil, dirt, detergents, etc.). The hydrophilic PU layer insures the mechanical strength of the material.
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Waterproof and Water Repellent Textiles and Clothing
Fig. 1.9 Compact hydrophilic layer (SYMPATEX membrane) (Loghin, 1998).
To describe the different behaviour in relation to liquid water and vapours (the principle of membranes waterproof-breathable), there are certain considerations regarding the type, average diameter, form and distribution of the pores. Considering their type, the pores can be (i) individual; closed, partially closed or open (see Fig. 1.10); (ii) distributed in a net, communicating between them and with both sides of the membrane, this being the typical structure of materials coated with microporous PU. Considering the average diameter, the pores can be divided into (Colleoni et al., 2015): (i) macropores, with diameter over 50 nm and specific surface 0.5–2 m2 g1; (ii) mesopores, with diameter between 2 nm and 50 nm and specific surface 20–150 m2 g1; and (iii) micropores, with diameter under 2 nm (comparable to small molecules) and specific surface 400–900 m2 g1. The structures with pore dimensions less than 103 nm are considered microporous, while the ones with dimensions exceeding 103 nm are considered foams.
Fig. 1.10 Porous coating polymer (SEM image 600) (Loghin, 1998).
Introduction to waterproof and water repellent textiles
21
Environment Fog
Light rain
Rain
Downpour
100 µm 500 µm 2000 µm 3000 µm
25 µm 20 nm
Water vapor
0.1 nm
Body surface
Fig. 1.11 The principle of microporous membranes.
Fig. 1.11 presents the principle of microporous membranes (Loghin, 1998). Laminated and coated microporous materials have pores with much lower dimensions (2–50 nm) than the smallest rain drop (fog 100 μm), but bigger than the water molecules (0.1–10 nm) (Ahn et al., 2010). Taking into consideration the dimensions and density, the pore distribution can be uniform or nonuniform. Analysis of the porosity of the outer layer is determinant in evaluating the level to which the garment will respond to the requirements during use.
1.3.3.4 Multifunctional waterproof fabrics Recent developments in the field of multifunctional materials refer to waterproof textiles with multiple functions. Apart from common repellent finishes (often c8-fluorocarbon giving both oil and water repellency while maintaining high breathability), such materials require other specific treatments to create multifunctionality. The outer layers of the coated and laminated waterproof textiles can be produced as a matrix-dispersed phase composite, the additional substances enlarging the range of possible applications where multiple functionality is required: – Waterproof-breathable and electrostatic shielding. The multifunctional material is manufactured by coating or laminating a multilayer knitted fabric made of carbon core filaments and PES/stainless steel spun yarns with microporous PU. The resulting material is waterproof-breathable, and water and oil repellent, while ensuring electrostatic shielding (Varnaite-Zuravliova et al., 2016). The antistatic characteristics of the waterproof-breathable material are given by adding Ag nanoparticles in the polymer mass (Shyr et al., 2011). – Water repellent and flame retardant. Cellulosic materials used for tent manufacturing are covered with hexagonal boron nitrite nanosheets; this treatment creates hydrophobic (θ > 90 angle) and flame retardant characteristics (Yaras et al., 2016).
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Waterproof and Water Repellent Textiles and Clothing
– Waterproof-breathable and UV barrier, antimicrobial and antistatic properties. The anti-UV, antimicrobial and antistatic properties of the waterproof materials are obtained by adding to the polymer mass nanoparticles like nano-silver, TiO2, ZnO, SiO2, Al2O3 and UV blockers (Gowri et al., 2010). – Waterproof-breathable with enhanced vapour transfer properties obtained by laminating with layers of electrospun nanowebs. The resulting materials have waterproof characteristics similar to materials laminated with Polytetrafluorethylene (PTFE, GoreTex) but also improved vapour permeability, making these materials suited for outdoor clothing (Ahn et al., 2010).
1.3.3.5
Ecological issues regarding waterproof-breathable and water repellent fabrics
A significant issue is the recycling and environmental impact of these materials. Some of the polymers or finishing agents are not biodegradable, certain chemicals used are toxic, and the manufacturing processes are energy-intensive. There are materials that have components of a common nature (like SYMPATEX that has PES substrate and hydrophilic polyester membrane) and can be recycled simultaneously. In most cases, the components have different chemical structures and their recycling requires separation and selection. Extracting, collecting and/or removing chemical substances from the macrostructure of the waterproof and water repellent materials represents a great challenge for the future.
1.4
Conclusions
In a wet environment, the basic requirement for garments is to keep the wearer dry by being waterproof and/or water repellent. Waterproof and water repellent materials have a large range of applications, being widely used for garment manufacturing in conventional garments for weather protection, uniforms and work wear, and clothing for sport and leisure. In contact with water, water repellent materials form drops that can be easily removed from the fabric surface. A water repellent fabric is resistant to wetting by water droplets and to the spreading of water over its surface. The water repellency of a fabric prevents the water absorption into the macrostructure of the fabric, with good influence on garment weight and fabric breathability. Waterproof materials for clothing must also ensure the wearer’s comfort, presenting the capacity to transfer water vapour from the microclimate through the garment system. Waterproof-breathable materials coated or laminated with microporous polymers or hydrophilic membranes are commonly used for this basic function. The materials with a compact outer layer are used for technical applications, and home and outdoor textiles, because their design includes specific requirements such as mechanical strength, biodegradability, resistance to biological agents or low weight.
References Ahn, H.W., Park, C.H., Chung, S.E., 2010. Waterproof and breathable properties of nanoweb applied clothing. Text. Res. J. 81 (14), 1438–1447.
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Chinta, S.K., Satis, D., 2014. Studies in waterproof breathable textiles. Int. J. Rec. Dev. Eng. Technol. 3 (2), 16–20. Colleoni, C., Guido, E., Migani, V., Rosace, G., 2015. Hydrophobic behavior of non-fluorinated sol-gel based cotton and polyester fabric coatings. J. Ind. Text. 44 (6), 815–834. Gibson, P., 2008. Water-repellent treatment on military uniform fabrics: physiological and comfort implications. J. Ind. Text. 38 (1), 43–53. Gowri, S.S., Almeida, L., Amorim, T., et al., 2010. Polymer nanocomposites for multifunctional finishing of textiles: a review. Text. Res. J. 80 (13), 1290–1306. Grand View Research Inc., 2016. Waterproof Breathable Textiles Market Size, WBT Industry Report 2024, 250 pp., Report ID: 978-1-68038-316-4. Gugliuzza, A., Drioli, E., 2013. A review on membrane engineering for innovation in wearable fabrics and protective textiles. J. Membr. Sci. 446, 350–375. Holmes, D., 2000. Performance characteristics of waterproof breathable fabrics. J. Ind. Text. 29 (4), 306–316. Houtman, R., 2015. Materials used for architectural fabric structures. In: Llorens, J. (Ed.), Fabric Structures in Architecture. first ed. Woodhead Publishing Series in Textiles. ISBN: 9781782422402, pp. 101–121. Indu Shekar, R., Kasturiya, N., Raj, H., Mathur, G.N., 2001. Studies on effect of water repellent treatment on flame retardant properties of fabric. J. Ind. Text. 30 (3), 222–254. Kale, K.H., Palaskar, S., 2010. Atmospheric pressure plasma polymerization of hexamethyldisiloxane for imparting water repellency to cotton fabric. Text. Res. J. 81 (6), 608–620. Kaynak, H.K., Babaarslan, O., 2012. Polyester microfilament woven fabrics. In: Jeon, H.-Y. (Ed.), Woven Fabrics. InTech Publisher, ISBN: 978-953-51-0607-4, pp. 155–178. Kuhr, M., Aibibu, D., Cherif, C., 2016. Targeted partial finishing of barrier textiles with microparticles, and their effects on barrier properties and comfort. J. Ind. Text. 45 (5), 853–878. Loghin, C., 2003. Sudarea materialelor textile (Welding of Textile Materials). Performantica Publishing House, Iaşi, ISBN: 973-7994-35-3. Loghin, C., Ciobanu, L. (Eds.), 2008. Iˆmbra˘ca˘minte funcționala˘—Modelarea și simularea funcțiilor de protecție. PIM Publishing House, Iasi, ISBN: 978-606-520-128-6, pp. 45–60. Loghin, C., Nicolaiov, P., Ionescu, I., Hoblea, Z., 2009. Functional design of equipments for individual protection. In: Proceedings of International Conference Management of Technological Changes. 2, ISBN: 978-960-89832-8-1, pp. 693–696. Loghin, C., 1998. Cerceta˘ri privind aplicarea procedeelor neconvenționale de asamblare la realizarea subansamblelor și produselor vestimentare (Research on the application of unconventional assembly processes for garments producing). Ph.D. Thesis, “Gheorghe Asachi” Technical University of Iasi, Doctoral School. Lynch, A., Strauss, M.D. (Eds.), 2015. Ethnic Dress in the United Stated: A Cultural Encyclopedia. Rowman & Littlefield Publishing Group Inc, USA, ISBN: 978-0-7591-2148-5. Mukhopadhyay, A., Midha, V.K., 2008a. A review on designing the waterproof breathable fabrics. Part I. Fundamental principles and designing aspects of breathable fabrics. J. Ind. Text. 37 (3), 225–262. Mukhopadhyay, A., Midha, V.K., 2008b. A review on designing the waterproof breathable fabrics. Part II. Construction and suitability of breathable fabrics for different uses. J. Ind. Text. 38 (1), 17–40. Park, S., Kim, J., Park, C.H., 2016. Influence of micro and nano-scale roughness on hydrophobicity of a plasma-treated woven fabric. Text. Res. J. (00), 1–15. https://doi.org/ 10.1177/0040517515627169.
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Waterproof and Water Repellent Textiles and Clothing
Purane, S.V., Panigrahi, N.R., 2007. Microfibres, microfilaments & their applications. AUTEX Res. J. 7 (3), 148–158. Sen, A.K., 2008. Coated Textiles: Principles and Applications. CRC Press, Taylor & Francis, ISBN: 9781420053456. pp. 175–200. Schuyten, H.A., David Reid, J., Weaver, J.W., 1948. Imparting water-repellency to textiles by chemical methods—a review of the literature. Text. Res. J. 18 (7), 396–398. Shephard, A., 2012. Waterproof dress: patents as evidence of design and function from 1880 through 1895. Cloth. Text. Res. J. 30 (3), 183–199. Sherif, F., Roedel, H., 2011. Technical textiles as a new route to enhance orthopedic casts’ properties. Int. J. Cloth. Sci. Technol. 23 (1), 25–33. https://doi.org/ 10.1108/09556221111096714. Singha, K., 2012. A review on coating & lamination in textiles: processes and applications. Am. J. Polym. Sci. 2 (3), 39–49. https://doi.org/10.5923/j.ajps.20120203.04. Shyr, T.W., Lien, C.H., Lin, A.J., 2011. Coexisting antistatic and water-repellent properties of polyester fabric. Text. Res. J. 81 (3), 254–263. Uludag, M.O., Ozcan, G., Unal, H., 2011. Disposable hydrophilic antimicrobial laminated nonwoven bed sheet. Int. J. Cloth. Sci. Technol. 23 (4), 222–231. Varnaite-Zuravliova, S., Sankauskaite, A., Stygiene, L., et al., 2016. The investigation of barrier and comfort properties of multifunctional coated conductive knitted fabrics. J. Ind. Text. 45 (4), 585–610. Yaras, A., Er, E., et al., 2016. Cellulosic tent fabric coated with boron nitride nanosheets. J. Ind. Text. 45 (6), 1689–1700. Zerdzicki, K., 2015. Durability evaluation of textile hanging roofs materials. Mechanical engineering [physics.class-ph]. Ph.D. Thesis, Universite d’Orleans. Zimmermann, J., Seeger, S., Reifler, F.A., 2009. Water shedding angle: a new technique to evaluate the water-repellent properties of superhydrophobic surfaces. Text. Res. J. 79 (17), 1565–1570.
Further reading Global Market Insights, 2012. Waterproof breathable textiles market, https://www.gminsights. com/pressrelease/waterproof-breathable-textiles-wbt-market. Hes, L., Loghin, C., 2009. Heat, moisture and air transfer properties of selected woven fabrics in wet state. J. Fiber Bioeng. Inform. 2 (3), 141–149. Hoblea, Z., 1999. Structuri textile—Structura și proiectarea ˆımbra˘ca˘mintei (Textile Structures—Garment Structure and Design). Gh. Asachi Publishing House, Iasi, ISBN: 973-99209-4-2, pp. 50–60. Lee, K., Cho, G., 2014. The optimum coating condition by response surface methodology for maximizing vapor-permeable water resistance and minimizing frictional sound of combat uniform fabric. Text. Res. J. 84 (7), 684–693. Loghin, C., 2013. Some aspects regarding the radio frequency welding of textile composites, bulletin of the polytechnic institute. Mech. Eng. 59 (1), 125–133. Loghin, C., Ursache, M., Mureșan, R., Mureșan, A., 2010. Surface treatments applied to textile materials and implications on their behaviour in wet conditions. Ind. Textila˘ 61 (6), 284–290.