Polymer blends

Polymer blends: state of art

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G. Markovic1, P.M. Visakh2 1Technical Rubber Goods, Pirot, Serbia; 2Tomsk Polytechnic University, Tomsk, Russia

1.1  General background on polymer blend/nanofiller composites Organic/inorganic composite materials have been extensively studied for a long time. When inorganic phases in organic/inorganic composites become nanosized, they are called nanocomposites. Organic/inorganic nanocomposites are generally organic polymer composites with inorganic nanoscale building blocks. They combine the advantages of the inorganic material (eg, rigidity, thermal stability) and the organic polymer (eg, flexibility, dielectric, ductility, and processability). Moreover, they usually also contain special properties of nanofillers leading to materials with improved properties. A defining feature of polymer nanocomposites is that the small size of the fillers leads to a dramatic increase in interfacial area as compared with traditional composites. This interfacial area creates a significant volume fraction of interfacial polymer with properties different from the bulk polymer even at low loadings [1]. A polymer blend is a mixture of two or more polymers that have been blended together to create a new material with different physical properties. Polymer blending has attracted much attention as an easy and cost-effective method of developing polymeric materials that have versatility for commercial applications. In other words, the properties of the blends can be manipulated according to their end use by correct selection of the component polymers [2]. Polymer blends have been intensively studied because of their theoretical and practical importance. In general, polymer blends are classified into either homogeneous (miscible on a molecular level) or heterogeneous (immiscible) blends. For example, poly(styrene) (PS)–poly(phenylene oxide) and poly(styrene-acrylonitrile)– poly(methyl methacrylate) (PMMA) are miscible blends, whereas poly(propylene) (PP)–PS and PP–poly(ethylene) (PE) are immiscible blends. Miscible (single-phase) blends are usually optically transparent and are homogeneous to the polymer segmental level. Single-phase blends also undergo phase separation that is usually brought about by variations in temperature, pressure, or in the composition of the mixture. Fillers are typically used to enhance specific properties of polymers, and the polymer/ nanocomposites based on nanoclays have gained attention because of their ability to improve the mechanical, thermal, barrier, and fire-retardant properties of polymers [3]. Nanosized fillers have been introduced in a wide spectrum of applications ranging from providing photocatalyst activation and conductivity to improve melting Recent Developments in Polymer Macro, Micro and Nano Blends. http://dx.doi.org/10.1016/B978-0-08-100408-1.00001-7 Copyright © 2017 Elsevier Ltd. All rights reserved.

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Recent Developments in Polymer Macro, Micro and Nano Blends

processability and moisture barrier properties. The special properties of nanoparticles are due to their size and high relative surface area-to-volume ratio. The optical clarity of a spherical nanosize particle is better than that of its equivalent conventional-size filler because the diameter is smaller than the wavelengths of light. Because a nanosize filler particle has a larger specific surface area than its analogous traditional-size filler particle, it interacts more with its surroundings [4]. Polymer blend/nanocomposites have been shown at lower or equal loadings to have properties that are equal or better than those of polymer composites with conventional filler. Inorganic nanoscale building blocks include nanotubes, layered silicates (eg, montmorillonite, saponite), nanoparticles of metals (eg, Au, Ag), metal oxides (eg, TiO2, Al2O3), semiconductors (eg, PbS, CdS), and so forth, among which SiO2 is viewed as being very important. The nanofillers featuring antibacterial properties, such as nanoscale titanium- and silver-based particles, could be applicable in filtration, hygiene, and hospital disposables applications or in consumer products. Thermodynamic stability of the polymer blend nanocomposite, which is due to the large interfacial phase between the matrix and the nanoparticle, yields the physical properties of the composite [5]. A polymer blend/nanocomposite can be defined as a polymer-nanofiller system in which the inorganic filler is on a nanometric scale at least in one dimension and it can be a polymer/nanoparticle blend or a hybrid. The composite interconnection can be based on a secondary force or physical entanglement [6]. In turn, the polymer/nanofiller hybrid is formed when the polymer and the nanoparticle are covalently bonded. The covalent bond can be formed during the in situ polymerization (the monomer or the growing polymer chain can react with the filler particle) or during the composite processing. Uniform filler distribution in the polymer blend matrix is desired. It can be a challenge to create a favorable interaction between the polymer and the nanofiller, and thus avoid phase separation and agglomeration of the filler particles. An example is the natural layered clay; it delaminates completely in water and in some polar polymer melts or solutions such as in polyamide, but it does not spontaneously disperse in nonpolar polyolefin melts such as PP melt. Two possible options for improving the compatibility of the components will be examined here: chemically modifying one or more of the components or introducing a suitable compatibilizer.

1.2  Nanoparticles of the polymer composites Nanoparticles exist in spherical, tube and whisker, and plate-like shapes and at least one of the three dimensions is required to be on a nanometric scale. Nanostructures of layered clays are further categorized as intercalated, in which the polymer chains have penetrated between the clay layers in a well-ordered multilayer morphology, and exfoliated, in which the clay layers have dispersed along the matrix and have no organized structure [7]. Carbon nanotubes also exhibit two nanostructures: single-walled nanotube and multiwalled nanotube, which is composed of several tubes within each other. Similar to the conventional filler particles, nanoparticles can be prepared by breaking up a large particle (nanoclays and other minerals) or by building them from the bottom up (carbon nanotubes and metal oxides). Regardless of the preparation method,

Polymer blends: state of art

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it is important to inhibit agglomeration of the nanoparticles and ensure good adhesion to the matrix. It is possible to coat or surface treat the nanosize particles [8] as done with microsize particles. A wide spectrum of polar agents (such as silanes and polyalcohols) and nonpolar agents (such as stearic acid and fatty acids) are commercially available coating agents for inorganic particles [9]. In contrast, layered nanoclays [10] and carbon nanotubes are surface treated. Surface treatment of nanoclays, which typically involves cation exchange, promotes delamination of the clay sheets in the matrix. The cation, or alternatively the intercalated media between the clay layers, determines the interlayer space, the gallery, and the cation exchange capacity [11].

1.3  Functionalized polymer with nanoparticles Polymer blends are utilized in various applications based on their properties. PP is used for its mechanical strength in consumer packages; poly(vinyl alcohol) is widely used for its water solubility and transparency in film applications on various paper and textile surfaces; and polyamide, in turn, is used for its good dimensional stability and chemical resistance in yarn applications [12]. Changes in a polymer’s structure can have a dramatic effect on its behavior, which is not always desired. Structure–property relationships can be illustrated by the following two examples: the solubility of poly(vinyl alcohol) is influenced by the degree of hydrolysis [13], and the moisture resistance of polyamide is dependent on the number of carbon atoms of the monomer used. The structure of a polymer can be modified by introducing functional groups to the polymer backbone and/or to the side chains [14] in various ways such as grafting [15] and using various different monomers in the polymerization reaction [16]. However, unwanted cross-linking and polymer degradation reactions can also be observed when postmodifying by melt-free radical grafting, which could be avoided by using polymerization techniques such as atomic transfer radical polymerization [17] and reversible-addition fragmentation chain transfer. For example, these offer intriguing new possibilities to produce the polymers and thereby polymer nanocomposites, such as initiating polymerization on the hydroxyl groups on the surface of a clay sheet. The monomers could be styrene, methyl methacrylate, or vinyl acetate [18]. In addition, developments in catalyst technology such as metallocene polyolefin polymerizations enable production of an excellent controlled comonomer distribution and stereospecificity along the polymer backbone or chain end [19]. If chemical treatment of the matrix polymer blend or the filler needs to be avoided or the interaction between the components is insufficient, then a third component, such as a polymer compatibilizer [20], can be added to the composite. Compatibilizers are added especially to polyolefin/nanoclay composites prepared by melt blending because the organo modification of the clay is seldom sufficient to create a favorable interaction between polymer chains and the clay sheets [21]. The interfacial adhesion between the compatibilizer and clay galleries is influenced by the functionality and its concentration, molecular weight and molecular weight distribution of the compatibilizer, and the mass ratio of the compatibilizer to the clay [22].

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Recent Developments in Polymer Macro, Micro and Nano Blends

1.4  Composite material It is necessary to make clear the terms hybrids and nanocomposites before the discussion of the nanocomposites because it is somewhat ambiguous to identify whether materials fall into nanocomposites or not. The most wide-ranging definition of a hybrid is a material that includes two moieties blended on the molecular scale. Commonly the term hybrids is more often used if the inorganic units are formed in situ by the sol–gel process. Meanwhile, use of the word nanocomposites implies that materials consist of various phases with different compositions, and at least one constituent phase (for polymer/silica nanocomposites, that phase is generally silica) has one dimension less than 100 nm. A gradual transition is implied by the fact that there is no clear borderline between hybrids and nanocomposites. Expressions of nanocomposites seem to be very trendy, and although the size of silica particles is greater than 100 nm, the composites are often called nanocomposites in some literature. Composites can be classified as particle-reinforced composites, in which particles are used as the reinforced phase, and fiber-reinforced composites, in which the reinforcing phase is in the form of fiber (Fig. 1.1). Fig. 1.1 illustrates the correlation among particle diameter, distance, and volume content. The particle-reinforced composites can be further classified into large-particle composites and dispersion-strengthened composites on the basis of particle size [23]. In polymer blend matrix composites, the matrix phase is polymer blend and the reinforcing phase can be metals, fibers, or ceramic particles. They are being used in various medical applications and sensing applications. The polymer blend composites can be classified into three categories: 1. Macrocomposites (10−2 m): Polymer macrocomposites are heterogeneous composites of polymers and macrosized fillers. The macroscopic characteristics of the composite often reflect its own microstructure. 2. Microcomposites (10−6 m): Composites using micron size fibers with high aspect ratio or fine hollow spheres or fibers as reinforcement are called microcomposites. The matrix can be any polymer. The reinforcing phase will be a continuous fiber or short fiber or micron sized fillers such as metal particles. The main advantage of using fibers is to improve strength, stiffness, and thermal stability of composites. 3. Nanocomposites (10−9 m): Polymer nanocomposites usually comprise the composites of polymers with dispersed inorganic nanofillers. The nanofiller can be an insulator, a semiconductor, or a metal, and it can have spherical, cylindrical, or flake shapes. The polymer (matrix) can be conductive or nonconductive in nature. 0DWUL[PDFURPROHFXOHV )LEHU &RPSRVLWH

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Figure 1.1  Length scales involved in multiscale modeling.

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The macroscopic characteristics of the composite often reflect its own microstructure. The properties of composites depend on the unique filler properties and on the morphology and interface features of the composite [24]. Such composites will exhibit interesting electric, optical, and magnetic properties. The characteristics of these systems depend on the compatibility of the constituents and the sizes of their contact surfaces. One of the challenges in preparing nanocomposite materials is to mix compatible and homogeneous nanofillers in a polymer matrix, guaranteeing or improving the matrix performance. With respect to manufacturing of polymeric nanocomposites, direct incorporation of inorganic nanoscale building blocks into polymers represents a typical way. However, because of the strong tendency of nanoparticles to agglomerate, nanosize fillers are hard to be uniformly dispersed in polymers by conventional techniques. The most important issue for producing nanocomposites lies in surface modification of the nanofillers. An ideal measure should be able to increase the hydrophobicity of the fillers, enhance the interfacial adhesion via physical interaction or chemical bonding, and eliminate the loose structure of filler agglomerates. In addition, the fragile nanoparticle agglomerates become stronger because they turn into a nanocomposite microstructure comprising the nanoparticles and the grafted and ungrafted (homopolymerized) polymer (Fig. 1.2). A series of works has been done in this field of growing interest for the purposes of improving the dispersibility of nanoparticles in solvents and their compatibility in polymers [25]. Mostly, the graft polymerization is conducted via two routes: (1) monomers are polymerized from active compounds (initiators or comonomers). PMMA is a commonly used thermoplastic matrix for fibers, sheets, and particles. There have been several studies on PMMA-fiber composites prepared by in situ polymerization [26], solution mixing [27], or melt blending [28]. The last one is already an industrial process for fabricating carbon fiber-reinforced thermoplastic composites. A combination of solvent casting and melt mixing allowed building composites with enhanced mechanical and electrical properties and exceptional fiber alignment [29]. Platelets and sheets also influence the composite’s thermal and mechanical

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Figure 1.2  Schematic drawing of the structural change of nanoparticle agglomerates before and after graft polymerization treatment.

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Recent Developments in Polymer Macro, Micro and Nano Blends

properties in relation to the material’s composition and dispersion state within the matrix [30]. Musbah et al. [31] discovered that nanopowders of phosphors Y2O3 (Eu3+) embedded in a PMMA matrix, prepared using a laboratory mixing molder, influence almost linearly the optical and dynamic mechanical properties of the nanocomposites. In fact, transmission electron microscopy (TEM) observation showed that the size of the dispersed phases increases with increasing filler content in the nanocomposites (Fig. 1.3). It should be noted here that the dispersed phases in the nanocomposites illustrated in Fig. 1.3(b)–(e) are clearly smaller than the untreated SiO2 (Fig. 1.3(a)), but they are still much larger than the size of the primary nano-SiO2 particles (7 nm). Therefore these dispersed phases are actually microcomposite agglomerates consisting of primary particles, grafting polymer, homopolymer, and a certain amount of matrix. These results contribute to a further understanding of the modified nanoparticles and their role in the composites.

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Figure 1.3  Transmission electron micrographs of poly(propylene)-based nanocomposites (MFI = 6.7g/10 mm) filled with (a) SiO2 as received (content of SiO2 = 1.96 vol%), (b) SiO2-g-poly(styrene) (PS; content of SiO2 = 1.96 vol%), (e) SiO2-g-PS (content of SiO2 = 6.38 vol%), (d) SiO2-g-poly(methyl methacrylate) (content of SiO2 = 1.96 vol%), and (e) (content of SiO2 = 6.38 vol%). Magnification = 2 × 104 [31].

Polymer blends: state of art

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Scheme 1.1  Three general approaches to prepare polymer/silica nanocomposites.

1.5  Preparation of polymer blend/nanofiller composites As pointed out by Hajji et al. [32], polymer blend nanocomposite systems can be prepared by various synthesis routes because of their ability to combine in different ways to introduce each phase. The organic component can be introduced as (1) a precursor, which can be a monomer or an oligomer; (2) a preformed linear polymer (in molten, solution, or emulsion states); or (3) a polymer network, physically (eg, semicrystalline linear polymer) or chemically (eg, thermosets, elastomers) cross-linked. The mineral part can be introduced as (1) a precursor (eg, tetraethyl orthosilicate) or (2) preformed nanoparticles. Organic or inorganic polymerization generally becomes necessary if at least one of the starting moieties is a precursor. Regardless of the preparation method of the polymer nanocomposite, a good compatibility between the components is essential to produce a homogenous polymer nanocomposite [33]. Compatibility can be improved by selecting suitable external blending conditions, such as by adjusting the temperature and the mixing intensity [34] or by chemical modifications of the filler and/or the polymer, as mentioned earlier. For example, Scheme 1.1 shows the three general preparative methods of polymer/ silica nanocomposites.

1.6  Characterization of polymer blend/nanocomposites The characterization methods used in the analysis of the chemical structure, microstructure, and morphology as well as the physical properties of the nanocomposites are varied. Many of these techniques are specific for characterization of particular properties of nanocomposites, and the properties of nanocomposites are also correspondingly discussed. To fully understand the structure–property relationships, several characterization techniques are often used. The properties of the polymer blend nanocomposites strongly depend on their composition, size of the particles, interfacial interaction, etc [35]. Chemical structure: The chemical structure of polymer/filler nanocomposites is generally identified by Fourier transform infrared and solid-state spectroscopy [36]. Microstructure and morphology: Crystallization behaviors of the polymer nanoparticlefilled composites are usually studied by differential scanning calorimetry (DSC).

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Recent Developments in Polymer Macro, Micro and Nano Blends

Mechanical properties: Because one of the primary reasons for adding inorganic fillers to polymers is to improve their mechanical performance, the mechanical properties of polymer nanocomposites are most concerned [37]. It is well known that one of the major requirements of polymer nanocomposites is to optimize the balance between the strength/stiffness and the toughness as much as possible. Therefore it is usually necessary to characterize the mechanical properties of nanocomposites from different viewpoints. Several criteria, including tensile strength, impact strength, flexural strength, hardness, fracture toughness, and so forth, have been used to evaluate the nanocomposites. Tensile, impact, and flexural properties: Tensile test is the most widely used method to evaluate the mechanical properties of the resultant nanocomposites, accordingly. Young’s modulus, tensile strength, and elongation at break are the three main parameters obtained. These vary with the silica content, but the variation trends are different. Furthermore, the impact test is also widely used for mechanical property characterization. Hardness: Hardness refers to the properties of a material resistant to various kinds of shape changes when force is applied. It is fundamental for many applications and is an important mechanical parameter of materials. There are three principal types of hardness: scratch hardness (resistance to fracture or plastic deformation due to friction from a sharp object), indentation hardness (resistance to plastic deformation due to impact from a sharp object), and rebound hardness (height of the bounce of an object dropped on the material). There are several different definitions of hardness, including Brinell hardness, Knoop hardness, Vickers hardness, Shore hardness, etc. Fracture toughness: Fracture toughness is a property that describes the ability of a material containing a crack to resist fracture. It is also one of the most important properties of materials. A parameter called stress intensity factor is used to determine the fracture toughness of most materials. As the stress intensity factor reaches a critical value (KIc), unstable fracture occurs. This critical value of the stress intensity factor is known as the fracture toughness of the material. Fracture toughness can be measured by different methods, such as single-edge notch bend and indentation fracture toughness. Friction and wear properties: Both friction and wear belong to the discipline of tribology. Friction is the force of two surfaces in contact or the force of a medium acting on a moving object, and wear is the erosion of material from a solid surface by the action of another solid. Factors that exert influence on friction and wear characteristics of polymer composites are the particle size, morphology, and concentration of the filler [38]. Thermal properties: Thermal properties are the properties of materials that change with temperature. They are studied by thermal analysis techniques, which include DSC, thermogravimetric analysis (TGA), differential thermal analysis (DTA), thermomechanical analysis (TMA), dynamic mechanical analysis (DMA)/dynamic mechanical thermal analysis (DMTA), dielectric thermal analysis, etc. As is well known, TGA/DTA and DSC are the two most widely used methods to determine the thermal properties of polymer nanocomposites. TGA can demonstrate the thermal stability, the onset of degradation, and the percentage of silica incorporated in the polymer matrix. DSC can be

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efficiently used to determine the thermal transition behavior of polymer/silica nanocomposites. Furthermore, the coefficient of thermal expansion (CTE), which is the criterion for the dimensional stability of materials, can be measured with TMA. In addition, thermal mechanical properties measured by DMA/DMTA are very important to understand the viscoelastic behavior of the nanocomposites. The storage modulus (G′), loss modulus (G″), and tan δ (G″/G′) are three important parameters of dynamic mechanical properties that can be used to determine the occurrence of molecular mobility transitions, such as the Tg. Dielectric thermal analysis is also useful to understand the viscoelastic behavior of the nanocomposites. In general, the incorporation of nanometer-sized inorganic particles into the polymer matrix can enhance the thermal stability by acting as a superior insulator and mass transport barrier to the volatile products generated during decomposition [39]. Meanwhile, the incorporation of nanometer-sized inorganic particles such as silica is very effective in decreasing the CTE of the polymer matrix. Flame-retardant properties: A fire retardant is used to make materials harder to ignite by slowing decomposition and increasing the ignition temperature. It functions by various methods such as absorbing energy away from the fire or preventing oxygen from reaching the fuel. Polymer nanocomposites for flame-retardant applications are attractive, and the nanoscale silica particle is a new type of nanoparticle for flameretardant nanocomposites [40]. The flammability behavior of polymer is defined on the basis of several processes or parameters, such as burning rates, spread rates, ignition characteristics, etc. Meanwhile, the flame-retardant characteristics of the nanocomposites are generally studied by measuring their limiting oxygen index (LOI). The LOI is defined as the minimum fraction of O2 in a mixture of O2 and N2 that will just support flaming combustion. Furthermore, the UL-94 test (Underwriter’s Laboratory Test #94) is conducted to quantify and rank the flame retardance of the materials. The UL-94 covers two types of testing: vertical burn and horizontal burn. The vertical burning test uses a Bunsen burner as the ignition source, and specimens are classified according to their burning times as V0 (best), V1, V2, or nonclassifiable (fail). The horizontal burning test is less severe, and specimens are classified as HB or fail accordingly. The horizontal burning test is also used to evaluate the fire-spread rate of materials by giving fire travel information on the horizontal surface, including fire-spread rate, burning behavior, and ease of extinction if the material burns without dripping. In addition, the cone calorimeter is one of the most effective bench-scale methods for studying the fire-retardant properties of polymeric materials such as the heat release rate, heat peak release rate, etc. Optical properties: The most important optical properties of a material are its transparency and refractive index. Transparency is the physical property allowing the transmission of light through a material. It is important for many practical applications of polymer nanocomposites. The refractive index is the ratio of speed of the light in vacuum to the speed of light in the medium. It is the most important property of optical systems that use refraction, and its can be measured by a refractometer. Gas transport properties: Gas transport properties include solubility, diffusivity, permeability, and permselectivity; detailed definitions of them can be found in the literature [41].

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Recent Developments in Polymer Macro, Micro and Nano Blends

Gas transport in nonporous polymer membranes typically proceeds by a solutiondiffusion mechanism in which the permeability (P) is given by S × D, where S and D denote the solubility and diffusivity of the permeating species, respectively. The solubility provides a measure of interaction between the polymer matrix and penetrant molecules, whereas the diffusivity describes molecule mobility, which is normally governed by the size of the penetrant molecule as it winds its way through the permanent and transient voids afforded by the free volume of the membrane [42]. Therefore gas transport has to be strongly dependent on the amount of free volume in the polymer matrix. In general, incorporating inert, nonporous fillers into a polymer membrane results in a decrease in its gas permeability because filler particles typically lower gas solubility and gas diffusivity within the polymer. For example, the permeability studies of thermally sprayed coatings measured using the permeability cup method (ASTM D1653-93) showed that the water vapor transmission rate through nanoreinforced coatings decreased by up to 50% compared with pure polymer coatings [43]. The aqueous permeability of coatings produced from smaller particle size polymers (D-30) was lower than the permeability of coatings produced from larger particles because of the lower porosities and higher densities achieved in D-30 coatings. Good permeability and selectivity of a membrane are commonly required in practical applications. Rheological properties: Rheology is the study of the deformation and flow of matter under the influence of an applied stress. The measurement of rheological properties is helpful to predict the physical properties of polymer nanocomposites during and after processing. Oberdisse [44] studied the rheological properties of a special nanocomposite material obtained by film formation of mixtures of colloidal silica and nanolatex solutions by means of uniaxial strain experiments. Electrical properties: Electrical properties of polymers include several electrical characteristics that are commonly associated with dielectric and conductivity properties. Electrical properties of nanofilled polymers are expected to be different when the fillers get to the nanoscale for several reasons. First, quantum effects begin to become important because the electrical properties of nanoparticles can change compared with the bulk. Second, as the particle size decreases, the interparticle spacing decreases for the same volume fraction. Therefore percolation can occur at lower volume fractions. In addition, the rate of resistivity decrease is lower than in micrometer-scale fillers. This is probably due to the large interfacial area and high interfacial resistance. Other characterization techniques: The particle size distributions of the colloidal nanocomposites can be assessed using two techniques: dynamic light scattering (DLS) and disk centrifuge photosedimentometry (DCP). The former technique reports an intensity-average diameter (based on the Stokes–Einstein equation), and the latter reports a weight-average diameter. Given the different biases of these two techniques, it is expected that the DLS diameters would always exceed the DCP diameters [45]. The size of the nanocomposite particles can also be estimated from the microscopy diagrams. X-ray photoelectron spectroscopy (XPS, also called electron spectroscopy for chemical analysis) is a surface analytical technique for assessing surface

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compositions. The sample is placed under high vacuum and is bombarded with X-rays, which penetrate into the top layer of the sample (approximately nanometers) and excite electrons (referred to as photoelectrons). Some of these electrons from the upper layer are emitted from the sample and can be detected. The electron binding energy is dependent on the chemical environment of the atom, making XPS useful to identify the elemental composition of the surface region. XPS is especially suitable to assess the surface compositions of colloidal particles because its typical sampling depth is only 2–5 nm. The XPS data combined with TEM studies of the ultramicrotomed particles can shed further light on the particle morphology. Armes et al. [46] reported a detailed XPS study of the surface compositions of selected vinyl polymer/ silica nanocomposites.

1.7  Applications of polymer blend/nanocomposites Polymer blend nanocomposites (Fig. 1.4) received significant attention because of the new and superior properties (eg, electrical, thermal, and mechanical) compared with conventional composites of these materials, and they may be synthesized using surprisingly simple and inexpensive techniques [47]. Various aspects can control the physicochemical properties of nanocomposites, such as the particle separation, the interphase interactions, the character of the polymer molecular structure, the method of the nanocomposite preparation, and so on [48]. )XWXUHRIQDQRWHFKQRORJ\

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Figure 1.4  The future of nanotechnology.








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Recent Developments in Polymer Macro, Micro and Nano Blends

As compared with neat polymers or microparticulate-filled polymer blend composites, polymer blend nanocomposites exhibit markedly improved properties, including modulus, strength, impact performance, and heat resistance at low concentration of the inorganic components (1–10 wt%). In this context, the nanocomposites are much lighter in weight and easier to be processed. Only the major structural applications areas are highlighted here and include the packaging industry; gas-sensing applications; the oil, aircraft, space, automotive, furniture, sporting goods, and marine industries; in infrastructure, electronics, and building construction; in the power and medical industries (eg, bone plates, implants); and in many other industrial products [49]. Coatings: In the past decade, scientists have paid attention to new types of coating— hybrid organic/inorganic coatings. These coatings combine the flexibility and easy processing of polymers with the hardness of inorganic materials and have been successfully applied on various substrates. In general, these hybrid coatings are transparent, show a good adhesion, and enhance the scratch and abrasion resistance of a polymeric substrate. Proton exchange membranes: The proton exchange membrane (PEM) is one of the major components in solid-type fuel cells, such as in PEM and direct methanol fuel cells. Up to now many research groups have reported the fabrication of polymer/silica nanocomposites as a PEM. Pervaporation membranes: In the pervaporation separation process, a liquid mixture is brought in direct contact with the feed side of the membrane, and the permeate is removed as vapor from the other side of the membrane. The mass flux is driven by maintaining the downstream partial pressure below the saturation pressure of the liquid feed solution. The transport of liquids through the membranes differs from other membrane processes such as gas separation because the permeants in pervaporation usually show high solubility in polymeric membranes. Encapsulation of organic light-emitting devices: Direct encapsulation of organic light-emitting devices (OLEDs) is realized by using highly transparent, photocurable, co-polyacrylate/silica nanocomposite resin. The feasibility of such a resin for OLED encapsulation was evaluated by physical/electrical property analysis of resins and driving voltage/luminance/lifetime measurement of OLEDs. Electrical property analysis revealed a higher electrical insulation of photocured nanocomposite resin film at 3.20 × 1012 Ù in comparison with that of oligomer film at 1.18 × 1012 Ù at 6.15 V to drive the bare OLED. Chemosensors: An approach for preparing polydiacetylene/silica nanocomposite for use as a chemosensor was reported. Metal uptake: The nanocomposites of electroactive polymers polyaniline (PANI) or polypyrrole (PPy) with ultrafine SiO2 particles have potential commercial applications for metal uptake because they possess a surface area substantially higher than that estimated from the particle size; hence they can aid the process of metal uptake. The progress in doing things much smaller, lighter, and faster than before, but it already been existed and already been going on for many years. This enhanced exactness could facilitate existing products and processes to be more effective/ cost-effective, hence requiring less raw materials and energy. This is especially true in fields such as information technology; electronics and energy industry; and space, medical, military, and security fields.

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