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Improving the wettability of polyester fabric with using direct fluorination
Journal of Fluorine Chemistry 219 (2019) 115–122
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Improving the wettability of polyester fabric with using direct fluorination N.P. Prorokova , T.Y. Kumeeva, S.Y. Vavilova ⁎
T
G.A. Krestov Institute of Solution Chemistry of Russian Academy of Science, Ivanovo, Akademicheskaya Str., 1, 153045, Russia
ARTICLE INFO
ABSTRACT
Keywords: Polyester fabric Direct fluorination Wettability Surface energy Water absorption Capillarity Tensile strength Antimicrobial properties
The ability to impart an improved wettability to polyester fabric as a result of direct fluorination has been demonstrated. A surface energy of the fluorinated polyester material was calculated; its specific surface area and porosity was measured. The change in water absorption and capillarity of the fluorinated fabric was analyzed. The effect of direct fluoridation on the tensile strength of the fabric and its barrier antimicrobial properties was evaluated.
1. Introduction Fibers based on polyethylene terephthalate (polyester) are the most popular textile materials. In 2014, the world demand for them was USD 73.5 billion, and in 2020 it is expected to be USD 115.0 billion [1]. Polyester (PL) fibers and fabrics have a complex of good consumer properties - high strength, wear resistance, heat resistance, low deformability, etc. However, they have some drawbacks. In particular, a serious drawback, which reduces the comfort of wearing products made of PL fibers, is their low wettability. Improving the wettability of the PL fibrous materials can be achieved by modifying them. There are two main groups of methods for increasing the hydrophilicity of PL fabrics. These include plasma treatment (plasma method) [2–4] and surface hydrolysis under the action of alkalis (chemical method) [5,6]. These methods have major drawbacks (high energy consumption, large mass loss, reduced fabric strength, etc.). Therefore, the problem of increasing hydrophilicity of PL fabric still remains relevant. One of the promising methods of surface modification of polymeric materials is a direct gas fluorination [7–15]. Its main advantage is low energy consumption: the process can take place at a room temperature without use of initiators. Environmental safety of the process is achieved through fluoridation in hermetically sealed reactors. Direct fluorination is the process of heterogeneous interaction of gaseous molecular fluorine or its mixtures with an inert gas and / or oxygen with a surface of a polymer material. The process is based on the sub-
⁎
stitution reaction of hydrogen atoms to fluorine atoms in macromolecules of polymers. The direct fluorination of polymers is a chainradical process [7,13]. As a result, a very thin (0.01–10 μm), partially fluorinated layer is formed on the surface of the polymer material [7,16,17]. Fluorination can improve a number of properties of polymer products. Although fluoridation is mainly used to reduce surface energy, methods for using it to increase the surface energy (and wettability) of polymers [18] are also known. In our work [19] it was shown that as a result of fluorination the polymeric material can also acquire antimicrobial properties. Along with the main reaction during the fluorination of polymeric materials indirect reactions can occur. These include the crosslinking, destruction and oxidation of polymer macromolecules [7,13]. These processes can affect the strength of polymer materials. The conditions of the fluorination process (the composition of the gas mixture, the fluorine pressure, the duration of the process, etc.) largely determine the characteristics of the fluorinated polymer [20]. Fluorination can be used to modify a wide range of polymer products [12–17]. In particular, a number of papers [19,21] are devoted to the direct fluorination of fibrous materials based on polypropylene. However, the fluorination of PL fibrous materials has not yet been studied. The purpose of this paper was to assess the possibility of using direct fluorination for improved wettability and imparting of antimicrobial properties of PL fibrous materials with maintaining their strength at the initial level.
Corresponding author. E-mail address: [email protected] (N.P. Prorokova).
https://doi.org/10.1016/j.jfluchem.2019.01.002 Received 4 November 2018; Received in revised form 5 January 2019; Accepted 7 January 2019 Available online 11 January 2019 0022-1139/ © 2019 Elsevier B.V. All rights reserved.
Journal of Fluorine Chemistry 219 (2019) 115–122
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2. Materials and methods 2.1. Fluorination procedure We carried out the direct fluorination in static conditions in closed vessels. The fluorination equipment was fabricated from low-carbon steel, stainless steel and Teflon. We placed the polymer sample inside the vessel, rarefy (residual vapor pressure was less than 0.05 Pa) and the vessel was filled with fluorinating mixture. Fluorine consumption was always less than 20% during fluorination. After evacuation of fluorinating mixture we removed the sample from the vessel and tested the sample. Fluorination was carried out at room temperature (20 ± 2) o C. The duration of the fluoridation process was 3–15 minutes. To prevent destruction of the polymer during fluorination, we limited the amount of fluorine to 10% and used it in a mixture with nitrogen. Fig. 1. MATR FTIR spectra of PL film: 1 - untreated; 2 - treated with gas mixture (10% F2 + 90% N2) at a total pressure of the mixture of 0.002 MPa, a temperature of 20 °C during 15 min., and 3 - the difference spectrum calculated by the formula: spectrum (3) = spectrum (2) - 0.55 • spectrum (1).
2.2. Materials Amount of impurities in F2 was less than 0.1 vol % (mainly oxygen). N2 and O2 were of 99.999 – 99.99% purity. As the objects of study we used a PL fabric with a mass of 175 g / m2, a surface density of 180 ± 10 g / m2 and a number of threads of 216 ± 4 per 10 cm in the warp and 203 ± 4 per 10 cm in the weft ("Y.R.C. Textile Co., Ltd", Bangkok, Thailand) and PL sewing thread of linear density 25 tex ("Euronit", Moscow, Russia). In some experiments we used a PL film with a thickness of 15 μm ("Pak-Trade", Ivanovo, Russia) as a model of fibrous material.
characterize the change in the chemical composition of the near-surface layer of the polymer material. Fig. 1 shows the spectra of the untreated (1), fluorinated (2) PL film and the difference spectrum (3). A diffuse band of 1140–1210 см−1 is observed in the spectra (2) and (3). This indicates the formation of C-Fn groups, where n = 1, 2 and 3 [24]. A diffuse band of 1760 - 1780 cm-1 was also detected. This band is corresponded to the absorption of the C]O (OH) groups with different surroundings. In the spectra of fluorine-treated polymers, the absorption of the -FC = O groups is usually recorded. These groups quickly undergo hydrolysis under the influence of atmospheric moisture. Within several tens of minutes, they are converted into the groups -C = O (OH) [13,15]:
2.3. Testing equipment Infrared spectra we measured by FTIR spectrometer “Nicollet” type “Avatar ESP 360″ equipped with MATR ZnSe accessory (45°) at 4 cm−1 resolution. Water contact angles we measured by conventional OwensWendt method [22]. Surface texture wе studied by atomic force microscope Solver P 47-PRO (“NT-MDT”). The specific surface area and pore sizes we determined using a device for measuring the sorption of gases "NOVA 4200e" ("Quantacrome"). For measurements we used nitrogen as an adsorbate. The water absorption and the capillarity of fabric we determined in accordance with GOST 3816-81 (ISO 811-81). Mechanical tests (tensile and elongation strength) we carried out using the test equipment 2099-P-5 (“Tochpribor”). Threads we tested in accordance with GOST 6611.2-73 (ISO 2062-72, ISO 6939-88). The length of the threads was 250 mm, the used stretching rate was 300 mm / min. Fabrics we tested in accordance with GOST R 53226-2008 (ISO 9073, ISO 10319). The samples of fabric were 200 mm long and 50 mm wide. The used stretching rate was 300 mm / min. The antimicrobial properties of PL fabric were determined using typical test cultures: Staphylococcus aurous (Gram-positive bacteria), Escherichia coli strain M17 (Gram-negative bacteria) and Candida albicans (conditionally pathogenic microfungi). We used the modified microbiological test ASTM E 2149 [23]. Within this test we placed chopped PL fabric in physiological solution contained appropriate microbes. In 24 h the amount of grown microbes’ colonies should have been counted. To avoid mistakes of counting we measured the amount of grown colonies by changing in turbidity of the solution (method of nephelometry). It is known that radicals with a short lifetime can form during fluorination [7,12–17]. Their presence affects all the performance characteristics of the polymer material. Therefore, we determined the characteristics of fluorinated PL materials no earlier than 30 days after fluorination, after the full recombination of short-lived radicals.
-FC = O + H2O→ -C = O(OH) + HF. In connection with the appearance of strongly polar groups -C = O (OH), we assumed that as a result of fluorination the polar component of the surface energy will increase, the adhesive capacity will improve and the wettability will increase. The water contact angle is one of the main characteristics of wettability of surfaces (Θ). We measured it using the traditional OwensWendt method [22]. To exclude the influence on the wetting process of the capillary-porous structure of the sample, the water contact angles of the modified PL material we determined on the film. The results are shown in Table 1. From the table it follows that as a result of fluorination of the PL film with a gas mixture without oxygen, the water contact angle of the film increases. Treatment with a gas mixture containing oxygen results in a reduction in the water contact angle of the film. A more complete picture of the trends in the changes of the wettability and adhesion properties of the PL materials after fluorination was obtained on the basis of the calculation of the total surface energy Table 1 The water contact angle of a PL film modified by method of direct fluorination at a total pressure of the gas mixture of 0.002 Mpa.
3. Results and discussion The formation of fluorine-containing groups on the surface of the PL material was confirmed by IR spectroscopy. We used the Multiple Attenuated Total Refection (MATR) FTIR spectrum, which allows us to 116
Fluorinating mixture and treatment duration
Water contact angle, degrees
Untreated PL film Gas mixture (10 % Gas mixture (10 % Gas mixture (10 % 3 min. Gas mixture (10 % 15 min.
F2 + 90 % N2), 3 min. F2 + 90 % N2), 15 min. F2 + 80 % N2 + 10 % O2),
72 81 82 66
F2 + 80 % N2 + 10 % O2),
67 ± 3
± ± ± ±
3 3 3 3
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(γ) of the modified PL film and its polar (γp) and dispersive (γd) components. A successful choice of fluorination parameters can provide conditions for a significant increase of a surface energy. As a result, the adhesion of the modified material will increase, including the ability to adsorb water molecules. To obtain the correct results, we used a PL film with a smooth surface. We measured wetting contact angles of the film surface with two liquids with different values of the dispersion and polar components of the surface tension: water (surface tension 72.8 mJ / m2) and α-bromonaphthalene (surface tension 44.6 mJ / m2 [25]). The following system of equations was solved:
1 + cos
2
(
sol 1/2 liq 1/2 (d ) d ) liq
+
(
sol 1/2 liq 1/2 ( p ) p ) liq
takes place. This indicates deceleration of the fluorination process and the formation of a fewer fluorine-containing groups in the presence of oxygen. This conclusion is confirmed by the results of fluorine mapping in EDX analysis (Fig. 4). It can be seen from the figure that PL fabrics fluorinated without oxygen contain more fluorine than fabrics fluorinated in the presence of oxygen. The ability of the fluorinated PL fabric to absorb and retain liquid was evaluated by the value of its water absorption. Water absorption is the amount of liquid absorbed by a sample when it is completely immersed in water for 1 h. Measurement results of the water absorption are shown in Table 3. It follows from the table that the water absorption of the modified fabric increases by 6–26 %, and it increases with the duration of fluorination. This is due to the formation of an additional amount of OH groups as a result of the destruction of polyethylene terephthalate molecules by the ester bond. Their presence may lead to an increase in the adsorption of water. In addition, the composition of the fluorinating mixture has a significant effect on the value of water absorption. It can be seen from the table that the water absorption of the PL fabric becomes significantly higher after fluorination in the presence of oxygen. The maximum water absorption has a PL fabric, fluorinated with a gas mixture of composition (10% F2 + 10% O2 + 80% N2) during 15 min. If the value of water absorption gives an idea of the total amount of liquid that the fabric can hold, then the intensity of absorption of liquid by the fabric is described by capillarity. Capillarity is also one of the most important qualitative characteristics of fibrous material and it is determined by the height of lifting of the colored liquid on the sample [28,29]. In fabrics, made of natural fibers, the liquid rise inside the pores and in the inter-fiber space. Polyester fibers do not have pores. Therefore, the capillarity of the PL fabric is characterized only by the rise of liquid between the fibers that form the fabric. The capillarity of the fluorinated PL fabric is shown in Fig. 5. To clarify the reasons for this phenomenon, we estimated the influence of the fluorination on the value of the inter-fiber space of the PL fabric. For this purpose we determined the specific surface area and the sizes of inter-fiber capillaries by capillary nitrogen condensation. A typical isotherm of nitrogen adsorption by the example of a sample fluorinated with a gas mixture of composition (10% F2 + 90% N2) is shown in Fig. 6. The specific surface area and the size of inter-fiber capillaries of fluorinated PL fabrics are presented in Table 4. It follows from the table that there is no increase in the diameter of inter-fiber capillaries of the PL fabric after fluoridation. Apparently, the water molecules are adsorbed by the hydrophilic groups, additionally formed on the PL fibers as a result of fluorination. It can be assumed that this process causes a decrease in the rate of liquid rising along the longitudinal capillaries of fluorinated PL fabric. The high water absorption of the fabric proves good sorption properties of PL fabric modified by the direct gas fluorination. The good wetting of the fluorinated fabric is proved by the increase in the water contact angles and the increase in the surface energy of the samples fluorinated with an oxygen-containing gas mixture. We checked whether the destruction and the oxidation of the polymer macromolecules [7,13], have not a negative effect on the tensile strength and elongation at break of the PL sewing thread and fabric. The data are presented in Tables 5 and 6, respectively. It follows from the tables that fluorination leads to some decrease in the tensile strength and elongation at break of the PL materials. After fluorination of the PL sewing thread the decrease in tensile strength is stronger. Apparently, this is due to the high anisotropy of the structure of highly twisted PL sewing threads. This assumption is confirmed by a high variation coefficient for the ultimate tensile strength and the elongation at break of the PL sewing threads. The tensile strength and
,
where dsol is the dispersion component of the surface energy of a solid, liq sol d is the dispersion component of the surface energy of a liquid, p is the polar component of the surface energy of a solid,
liq p
is the polar
component of the surface energy of a liquid, and is the surface energy of a liquid. The unknowns in the equation are the polar and dispersion components of the surface energy of the solid ( dsol , psol ). When solving the system of equations, we obtained their values and the value of the surface energy of the solid phase: sol = dsol + psol . We determined the values of the total surface energy, its polar and dispersion components for the PL film, fluorinated under various conditions. We also estimated the effect of the duration of holding of the modified film in the air to the surface energy of the film and its components. The results are shown in Fig. 2. As can be seen from Fig. 2, in the fluorination of the PL material the values of its total surface energy and its polar component substantially increase. The dispersion component increases in a les degree. With an increase of the duration of fluoridation from 1 to 3 minutes to 15 min, this tendency is more pronounced. The addition of oxygen into the fluorinating mixture leads to a more significant increase in a surface energy compared to the use of mixtures without oxygen. This effect is associated with a formation of oxygencontaining functional groups on the surface of the polymer, which are characterized by a high surface energy. The trend identified for the PL coincides with the regularities for polypropylene and polyphenylene oxide [8,26] described in the literature. Fig. 2 shows that the PL film is characterized by a maximum high total surface energy immediately after the fluorination with an oxygencontaining mixture. When the fluorinated film is held in air, the total surface energy and its polar component slightly decrease. The dispersion component slightly increases when the film is stored in air. The surface energy is the main factor that determines the wettability of materials. The morphology of the surface has also a significant effect on wettability. The wetting of the surface of a smooth non-porous PL film proceeds in a homogeneous mode. In this case, the liquid contact with the entire surface of the solid and completely fills the hollows on it. As the PL film is hydrophilic (Θ < 90°), increasing the roughness will increase the wettability [27]. To assess how fluorination affects the roughness of the surface of PL materials, we investigated the morphology of the surface of fluorinated PL films by atomic force microscopy. The results are shown in Fig. 3. The figure reflects the visualized understanding of the surface of PL films and profile lines of their surfaces. We characterized the roughness using the root mean square - RMS, maximum (Hmax) and average (Hav) values. These data are presented in Table 2. It follows from the figure and table that the fluorinated PL film has a higher roughness than the untreated film. Consequently, the wettability of such film will be additionally increased. Besides, we can see that when processing with a fluorine-containing mixture without oxygen, a more significant, profound change in the morphology of the surface liq
117
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Fig. 2. The effect on the (a) total surface energy, (b) polar and (c) dispersion components of the surface energy of the PL film, the duration of its fluorination and the time of storage in air. 1 - untreated film; 2, 2', 2” - fluorination with a gas mixture (10 % F2 + 90% N2); 3, 3', 3” - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2). Duration of fluoridation: circle - 1 min.; triangle - 3 min.; square - 15 min.
elongation at break of the PL fabric after fluorination decrease slightly. The use of an oxygen-containing gas mixture for the fluorination of PL fibrous materials leads to a higher loss of the tensile strength. This is due to the low resistance of polyethylene terephthalate to the effects of oxidation. Thus, the maximum decrease in tensile strength of the fabric after fluorination is about 10%, the decrease in tensile strength of thread is about 15%. This decrease in strength is small, while the use of chemical and plasma methods of increasing hydrophilicity leads to a decrease in the strength of PL fabric by 30–40% [3–6]. In [19] we showed that a polypropylene fibrous material at the direct gas fluorination acquires the ability to inhibit the vital activity of either pathogenic bacteria or microfungi, depending on the composition of the gas mixture. In this paper we evaluated the effect of direct fluorination on the barrier antimicrobial properties of the PL fibrous material. Table 7 presents data about growth or inhibition of typical test cultures in contact with fluorinated PL fabric: Staphylococcus aureus and Escherichia coli strain M-17 - respectively gram-positive and gram -negative bacterial cultures, Candida albicans - yeast-like microscopic fungi. It follows from the table that as a result of fluorination the PL fabric acquires barrier antibacterial properties. They are weakly expressed after fluorination with a gas mixture without oxygen. The PL fabric acquires a sufficiently high antibacterial activity when treated with an oxygen-containing gas mixture. PL fabric after fluorination does not
have anti-fungal properties. The cause of the antibacterial action of the fluorinated surface of the PL fabric is apparently, a toxic effect on pathogenic microorganisms occurs when they come into direct contact with the surface of the modified material. The biochemical mechanism of the barrier antimicrobial action of fluorinated PL fabrics requires additional study. 4. Conclusions We have established that the fluorination of PL fibrous materials by a periodic method at room temperature and a pressure of 0.001 0.002 MPa with gas mixtures containing 10% fluorine leads to a significant change in the surface energy of the polymer material. Addition into the fluorinating mixture of 10% of oxygen leads to the formation on the surface of the PL material of an additional amount of oxygencontaining groups that provide an increase in the surface energy of the fiber and its wettability. As a result of fluorination the water absorption of the PL fiber material increases substantially. The maximum increase in water absorption (by 26%) is achieved using an oxygen-containing mixture for fluorination. In spite of increase of the number of oxygen-containing groups on the modified fibers, the rate of water rise along the longitudinal capillaries of the fabric slightly reduced. This is due to the adsorption of water molecules on the additional formed functional groups. The specific surface area of the PL fabric, as well as the size of inter-fiber capillaries, practically does not change. 118
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Fig. 3. Morphology of the PL film (1) and surface profiles (2): а - untreated; b - fluorination with a gas mixture (10% F2 + 90% N2) during 15 min.; c - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 15 min. Method of atomic force microscopy.
Table 2 Roughness characteristics of fluorinated PL films. Fluorinating mixture and treatment duration
RMS, nm
Hmax, nm
Hav, нм
Untreated PL film Gas mixture (10 % F2 + 90 % N2), 15 min. Gas mixture (10 % F2 + 80 % N2 + 10 % O2), 15 min.
2.1 ± 0.4 6.5 ± 1.3 3,5 ± 0,7
28.9 ± 1.3 76.9 ± 5.8 58.5 ± 2.8
13.1 ± 0.5 30.4 ± 2.9 22.9 ± 1.2
119
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Fig. 4. Fluorine mapping of PL fabric after fluorination within 15 min. Gas mixture: a - (10% F2 + 90% N2); b - (10% F2 + 80% N2 + 10% O2). EDX method. Table 3 Water absorption of a PL fabric modified by the direct fluorination at a total pressure of the gas mixture of 0.002 Mpa. Fluorinating mixture and treatment duration
Water absorption, %
Untreated PL fabric Gas mixture (10 % F2 Gas mixture (10 % F2 Gas mixture (10 % F2 Gas mixture (10 % F2
49.5 52.6 56.0 57.9 62.3
+ + + +
90 90 80 80
% % % %
N2), 3 min. N2), 15 min. N2 + 10 % O2), 3 min. N2 + 10 % O2), 15 min.
± ± ± ± ±
1.5 1.6 1.8 1.7 1.9
The tensile strength of the PL fabric after fluorination changes insignificantly. As a result of fluorination the PL fabric acquires barrier antibacterial properties. They are weakly expressed in the case of fluorination of the PL fabric with a gas mixture without oxygen and are sufficiently high when the PL fabric treated with an oxygen-containing gas mixture. Modified by direct fluorination PL fibrous material with improved wettability and high water adsorption can be used to produce a wide range of household products, upholstery materials and materials for the interior of vehicles.
Fig. 6. Isotherm of nitrogen adsorption by PL fabric, fluorinated with gas mixture (10% F2 + 90% N2) during 15 min. at a total pressure of the mixture 0.002 Mpa.
Fig. 5. Dependence of the liquid rise height by the warp (a) and by the weft (b) on the duration of the raising of the liquid for the PL fabric: 1 - untreated; 2 fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 3 min.; 3 - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 15 min. It follows from the figure that the rate of water rising along the longitudinal capillaries of the fabric decreases as a result of fluorination.
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Table 4 The specific surface area and the size of inter-fiber capillaries of the PL fabric modified by the direct fluorination at a total pressure of the gas mixture 0.002 MPa (method of capillary condensation of nitrogen). VALUE
Fluorinating mixture and treatment duration
Specific surface area, m2 / g Inter-fiber capillaries volume, cm3 / g Diameter of inter-fiber capillaries, nm
UNTREATED PL FABRIC
GAS MIXTURE (10 % F2 + 90 % N2), 15 min.
GAS MIXTURE (10 % F2 + 80 % N2 + 10 % O2), 15 min.
10.541 0.016 3.176
10.333 0.017 3.170
10.821 0.017 3.173
Table 5 The fluorination conditions influence on tensile strength and elongation at break of PL sewing thread. Fluorinating mixture and treatment duration
Ultimate tensile strength, MPa (cN/tex)
Variation coefficient for the ultimate tensile strength, %
Elongation at break, %
Variation coefficient for the elongation at break, %
Untreated PL sewing thread Gas mixture (10 % F2 + 80 % N2 + 10 % O2) 3 min. 15 min. Gas mixture (10 % F2 + 90 % N2) 3 min. 15 min.
39.0 ± 1.6
5.7
25.6 ± 0.7
3.7
25.3 ± 1.8 22.9 ± 2.0
10.0 12.3
22.0 ± 0.6 21.8 ± 1.1
4.0 7.0
26.8 ± 3.6 26.2 ± 2.7
14.6 18.8
25.3 ± 1.8 22.8 ± 0.9
5.4 10.1
Table 6 The fluorination conditions influence on tensile strength and elongation at break of PL fabric. Fluorinating mixture and treatment duration
Tensile strength, N
Variation coefficient for the tensile strength, %
Elongation at break, %
Variation coefficient for the elongation at break, %
Untreated PL fabric Gas mixture (10 % F2 + 80 % N2 + 10 % O2) 3 min. 15 min. Gas mixture (10 % F2 + 90 % N2) 3 min. 15 min.
366.4 ± 25.6
7.0
27.5 ± 1.1
3.3
332.6 ± 11.6 328.1 ± 24.3
3.5 5.4
23.5 ± 1.7 22.7 ± 0.8
5.8 3.0
352.5 ± 8.1 333.6 ± 13.3
2.3 4.1
24.3 ± 1.3 24.2 ± 1.9
4.4 6.2
Growth (+) or inhibition (-) of test pathogenic microorganisms,%
of Chemistry and Technology), O.Yu. Kuznetsov (Ivanovo State Medical Academy). The work was carried out using the equipment of the Centre for joint use of scientific equipment “The upper Volga region centre of physical and chemical research”.
bacteria
References
Table 7 The effect of fluorination on the barrier antimicrobial properties of PL fabric. Fluorinating mixture and treatment duration
Untreated PL fabric Gas mixture (10 % F2 + 80 % N2 + 10 % O2), 15 min. Gas mixture (10 % F2 + 90 % N2), 15 min.
microfungi Candida albicans
Escherichia coli
Staphylococcus aurous
0 −50
0 −90
0 +47
−28
−6
0
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Acknowledgements The work was carried out within the framework of the state contract with FASO of Russia № 01201260484. In the implementation of the study participated A.P. Kharitonov (Institute of Energy Problems of Chemical Physics (Division), Russian Academy of Sciences). The authors also thank for the participation in the experimental work A.S. Kraev, V.A. Istratkin (G.A. Krestov Institute of Solution Chemistry of Russian Academy of Science), I.V. Kholodkov (Ivanovo State University 121
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via direct fluorination, Surf. Coat. Technol. 292 (2016) 144–154. [19] N.P. Prorokova, V.A. Istratkin, T.Yu. Kumeeva, S.Yu. Vavilova, A.P. Kharitonov, V.M. Bouznik, Improvement of polypropylene nonwoven fabric antibacterial properties by the direct fluorination, RSC Adv. 5 (2015) 44545–44549. [20] A.P. Kharitonov, Improvement of performance characteristics of polymer materials by direct fluorination, Chem. Sust. Dev. 12 (2004) 625–630. [21] V. Vargha, A. Chetty, Z. Sulyok, J. Mihaґly, Z. Keresztes, A. Toґth, I. Sajoґ, L. Korecz, R. Anandjiwala, L. Boguslavsky, Functionalisation of polypropylene nonwoven fabrics (NWFs), J. Therm. Anal. Calorim. 109 (2012) 1019–1032. [22] D.K. Owens, R.C. Wendt, Estimation of the surface free energy of polymers, J. Appl. Polym. Sci. Symp. 13 (1969) 1741–1747. [23] ASTM E2149 - 10 Standard Test Method for Determining the Antimicrobial Activity of Immobilized Antimicrobial Agents Under Dynamic Contact Conditions. USA, (2001). [24] J. Dechant, R. Danz, W. Kimmer, R. Schmolke, Ultrarotspektroskopische Untersuchungen an Polymeren, Akademie-Verlag, Berlin, 1972. [25] D.W. van Krevelen, Properties of Polymers, Correlations With Chemical Structure, Von Elsevier Publication Company, Amsterdam-London-New York, 1972. [26] J.D. Le Roux, Surface fluorination of poly (phenylene oxide) composite membranes: part II. Characterization of the fluorinated layer, J. Membrane Sci. 90 (1994) 37–53. [27] L.B. Boinovich, A.M. Emelyanenko, Hydrophobic materials and coatings: principles of design, properties and applications, Russ. Chem. Rev. 77 (2008) 583–600. [28] Y.L. Hsieh, Liquid transport in fabric structures, Text. Res. J. 65 (1995) 299–307. [29] D. Rajagopalan, A.P. Aneja, J.M. Marchal, Modeling capillary flow in complex geometries, Text. Res. J. 71 (2001) 813–821.
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Improving the wettability of polyester fabric with using direct fluorination N.P. Prorokova , T.Y. Kumeeva, S.Y. Vavilova ⁎
T
G.A. Krestov Institute of Solution Chemistry of Russian Academy of Science, Ivanovo, Akademicheskaya Str., 1, 153045, Russia
ARTICLE INFO
ABSTRACT
Keywords: Polyester fabric Direct fluorination Wettability Surface energy Water absorption Capillarity Tensile strength Antimicrobial properties
The ability to impart an improved wettability to polyester fabric as a result of direct fluorination has been demonstrated. A surface energy of the fluorinated polyester material was calculated; its specific surface area and porosity was measured. The change in water absorption and capillarity of the fluorinated fabric was analyzed. The effect of direct fluoridation on the tensile strength of the fabric and its barrier antimicrobial properties was evaluated.
1. Introduction Fibers based on polyethylene terephthalate (polyester) are the most popular textile materials. In 2014, the world demand for them was USD 73.5 billion, and in 2020 it is expected to be USD 115.0 billion [1]. Polyester (PL) fibers and fabrics have a complex of good consumer properties - high strength, wear resistance, heat resistance, low deformability, etc. However, they have some drawbacks. In particular, a serious drawback, which reduces the comfort of wearing products made of PL fibers, is their low wettability. Improving the wettability of the PL fibrous materials can be achieved by modifying them. There are two main groups of methods for increasing the hydrophilicity of PL fabrics. These include plasma treatment (plasma method) [2–4] and surface hydrolysis under the action of alkalis (chemical method) [5,6]. These methods have major drawbacks (high energy consumption, large mass loss, reduced fabric strength, etc.). Therefore, the problem of increasing hydrophilicity of PL fabric still remains relevant. One of the promising methods of surface modification of polymeric materials is a direct gas fluorination [7–15]. Its main advantage is low energy consumption: the process can take place at a room temperature without use of initiators. Environmental safety of the process is achieved through fluoridation in hermetically sealed reactors. Direct fluorination is the process of heterogeneous interaction of gaseous molecular fluorine or its mixtures with an inert gas and / or oxygen with a surface of a polymer material. The process is based on the sub-
⁎
stitution reaction of hydrogen atoms to fluorine atoms in macromolecules of polymers. The direct fluorination of polymers is a chainradical process [7,13]. As a result, a very thin (0.01–10 μm), partially fluorinated layer is formed on the surface of the polymer material [7,16,17]. Fluorination can improve a number of properties of polymer products. Although fluoridation is mainly used to reduce surface energy, methods for using it to increase the surface energy (and wettability) of polymers [18] are also known. In our work [19] it was shown that as a result of fluorination the polymeric material can also acquire antimicrobial properties. Along with the main reaction during the fluorination of polymeric materials indirect reactions can occur. These include the crosslinking, destruction and oxidation of polymer macromolecules [7,13]. These processes can affect the strength of polymer materials. The conditions of the fluorination process (the composition of the gas mixture, the fluorine pressure, the duration of the process, etc.) largely determine the characteristics of the fluorinated polymer [20]. Fluorination can be used to modify a wide range of polymer products [12–17]. In particular, a number of papers [19,21] are devoted to the direct fluorination of fibrous materials based on polypropylene. However, the fluorination of PL fibrous materials has not yet been studied. The purpose of this paper was to assess the possibility of using direct fluorination for improved wettability and imparting of antimicrobial properties of PL fibrous materials with maintaining their strength at the initial level.
Corresponding author. E-mail address: [email protected] (N.P. Prorokova).
https://doi.org/10.1016/j.jfluchem.2019.01.002 Received 4 November 2018; Received in revised form 5 January 2019; Accepted 7 January 2019 Available online 11 January 2019 0022-1139/ © 2019 Elsevier B.V. All rights reserved.
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2. Materials and methods 2.1. Fluorination procedure We carried out the direct fluorination in static conditions in closed vessels. The fluorination equipment was fabricated from low-carbon steel, stainless steel and Teflon. We placed the polymer sample inside the vessel, rarefy (residual vapor pressure was less than 0.05 Pa) and the vessel was filled with fluorinating mixture. Fluorine consumption was always less than 20% during fluorination. After evacuation of fluorinating mixture we removed the sample from the vessel and tested the sample. Fluorination was carried out at room temperature (20 ± 2) o C. The duration of the fluoridation process was 3–15 minutes. To prevent destruction of the polymer during fluorination, we limited the amount of fluorine to 10% and used it in a mixture with nitrogen. Fig. 1. MATR FTIR spectra of PL film: 1 - untreated; 2 - treated with gas mixture (10% F2 + 90% N2) at a total pressure of the mixture of 0.002 MPa, a temperature of 20 °C during 15 min., and 3 - the difference spectrum calculated by the formula: spectrum (3) = spectrum (2) - 0.55 • spectrum (1).
2.2. Materials Amount of impurities in F2 was less than 0.1 vol % (mainly oxygen). N2 and O2 were of 99.999 – 99.99% purity. As the objects of study we used a PL fabric with a mass of 175 g / m2, a surface density of 180 ± 10 g / m2 and a number of threads of 216 ± 4 per 10 cm in the warp and 203 ± 4 per 10 cm in the weft ("Y.R.C. Textile Co., Ltd", Bangkok, Thailand) and PL sewing thread of linear density 25 tex ("Euronit", Moscow, Russia). In some experiments we used a PL film with a thickness of 15 μm ("Pak-Trade", Ivanovo, Russia) as a model of fibrous material.
characterize the change in the chemical composition of the near-surface layer of the polymer material. Fig. 1 shows the spectra of the untreated (1), fluorinated (2) PL film and the difference spectrum (3). A diffuse band of 1140–1210 см−1 is observed in the spectra (2) and (3). This indicates the formation of C-Fn groups, where n = 1, 2 and 3 [24]. A diffuse band of 1760 - 1780 cm-1 was also detected. This band is corresponded to the absorption of the C]O (OH) groups with different surroundings. In the spectra of fluorine-treated polymers, the absorption of the -FC = O groups is usually recorded. These groups quickly undergo hydrolysis under the influence of atmospheric moisture. Within several tens of minutes, they are converted into the groups -C = O (OH) [13,15]:
2.3. Testing equipment Infrared spectra we measured by FTIR spectrometer “Nicollet” type “Avatar ESP 360″ equipped with MATR ZnSe accessory (45°) at 4 cm−1 resolution. Water contact angles we measured by conventional OwensWendt method [22]. Surface texture wе studied by atomic force microscope Solver P 47-PRO (“NT-MDT”). The specific surface area and pore sizes we determined using a device for measuring the sorption of gases "NOVA 4200e" ("Quantacrome"). For measurements we used nitrogen as an adsorbate. The water absorption and the capillarity of fabric we determined in accordance with GOST 3816-81 (ISO 811-81). Mechanical tests (tensile and elongation strength) we carried out using the test equipment 2099-P-5 (“Tochpribor”). Threads we tested in accordance with GOST 6611.2-73 (ISO 2062-72, ISO 6939-88). The length of the threads was 250 mm, the used stretching rate was 300 mm / min. Fabrics we tested in accordance with GOST R 53226-2008 (ISO 9073, ISO 10319). The samples of fabric were 200 mm long and 50 mm wide. The used stretching rate was 300 mm / min. The antimicrobial properties of PL fabric were determined using typical test cultures: Staphylococcus aurous (Gram-positive bacteria), Escherichia coli strain M17 (Gram-negative bacteria) and Candida albicans (conditionally pathogenic microfungi). We used the modified microbiological test ASTM E 2149 [23]. Within this test we placed chopped PL fabric in physiological solution contained appropriate microbes. In 24 h the amount of grown microbes’ colonies should have been counted. To avoid mistakes of counting we measured the amount of grown colonies by changing in turbidity of the solution (method of nephelometry). It is known that radicals with a short lifetime can form during fluorination [7,12–17]. Their presence affects all the performance characteristics of the polymer material. Therefore, we determined the characteristics of fluorinated PL materials no earlier than 30 days after fluorination, after the full recombination of short-lived radicals.
-FC = O + H2O→ -C = O(OH) + HF. In connection with the appearance of strongly polar groups -C = O (OH), we assumed that as a result of fluorination the polar component of the surface energy will increase, the adhesive capacity will improve and the wettability will increase. The water contact angle is one of the main characteristics of wettability of surfaces (Θ). We measured it using the traditional OwensWendt method [22]. To exclude the influence on the wetting process of the capillary-porous structure of the sample, the water contact angles of the modified PL material we determined on the film. The results are shown in Table 1. From the table it follows that as a result of fluorination of the PL film with a gas mixture without oxygen, the water contact angle of the film increases. Treatment with a gas mixture containing oxygen results in a reduction in the water contact angle of the film. A more complete picture of the trends in the changes of the wettability and adhesion properties of the PL materials after fluorination was obtained on the basis of the calculation of the total surface energy Table 1 The water contact angle of a PL film modified by method of direct fluorination at a total pressure of the gas mixture of 0.002 Mpa.
3. Results and discussion The formation of fluorine-containing groups on the surface of the PL material was confirmed by IR spectroscopy. We used the Multiple Attenuated Total Refection (MATR) FTIR spectrum, which allows us to 116
Fluorinating mixture and treatment duration
Water contact angle, degrees
Untreated PL film Gas mixture (10 % Gas mixture (10 % Gas mixture (10 % 3 min. Gas mixture (10 % 15 min.
F2 + 90 % N2), 3 min. F2 + 90 % N2), 15 min. F2 + 80 % N2 + 10 % O2),
72 81 82 66
F2 + 80 % N2 + 10 % O2),
67 ± 3
± ± ± ±
3 3 3 3
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(γ) of the modified PL film and its polar (γp) and dispersive (γd) components. A successful choice of fluorination parameters can provide conditions for a significant increase of a surface energy. As a result, the adhesion of the modified material will increase, including the ability to adsorb water molecules. To obtain the correct results, we used a PL film with a smooth surface. We measured wetting contact angles of the film surface with two liquids with different values of the dispersion and polar components of the surface tension: water (surface tension 72.8 mJ / m2) and α-bromonaphthalene (surface tension 44.6 mJ / m2 [25]). The following system of equations was solved:
1 + cos
2
(
sol 1/2 liq 1/2 (d ) d ) liq
+
(
sol 1/2 liq 1/2 ( p ) p ) liq
takes place. This indicates deceleration of the fluorination process and the formation of a fewer fluorine-containing groups in the presence of oxygen. This conclusion is confirmed by the results of fluorine mapping in EDX analysis (Fig. 4). It can be seen from the figure that PL fabrics fluorinated without oxygen contain more fluorine than fabrics fluorinated in the presence of oxygen. The ability of the fluorinated PL fabric to absorb and retain liquid was evaluated by the value of its water absorption. Water absorption is the amount of liquid absorbed by a sample when it is completely immersed in water for 1 h. Measurement results of the water absorption are shown in Table 3. It follows from the table that the water absorption of the modified fabric increases by 6–26 %, and it increases with the duration of fluorination. This is due to the formation of an additional amount of OH groups as a result of the destruction of polyethylene terephthalate molecules by the ester bond. Their presence may lead to an increase in the adsorption of water. In addition, the composition of the fluorinating mixture has a significant effect on the value of water absorption. It can be seen from the table that the water absorption of the PL fabric becomes significantly higher after fluorination in the presence of oxygen. The maximum water absorption has a PL fabric, fluorinated with a gas mixture of composition (10% F2 + 10% O2 + 80% N2) during 15 min. If the value of water absorption gives an idea of the total amount of liquid that the fabric can hold, then the intensity of absorption of liquid by the fabric is described by capillarity. Capillarity is also one of the most important qualitative characteristics of fibrous material and it is determined by the height of lifting of the colored liquid on the sample [28,29]. In fabrics, made of natural fibers, the liquid rise inside the pores and in the inter-fiber space. Polyester fibers do not have pores. Therefore, the capillarity of the PL fabric is characterized only by the rise of liquid between the fibers that form the fabric. The capillarity of the fluorinated PL fabric is shown in Fig. 5. To clarify the reasons for this phenomenon, we estimated the influence of the fluorination on the value of the inter-fiber space of the PL fabric. For this purpose we determined the specific surface area and the sizes of inter-fiber capillaries by capillary nitrogen condensation. A typical isotherm of nitrogen adsorption by the example of a sample fluorinated with a gas mixture of composition (10% F2 + 90% N2) is shown in Fig. 6. The specific surface area and the size of inter-fiber capillaries of fluorinated PL fabrics are presented in Table 4. It follows from the table that there is no increase in the diameter of inter-fiber capillaries of the PL fabric after fluoridation. Apparently, the water molecules are adsorbed by the hydrophilic groups, additionally formed on the PL fibers as a result of fluorination. It can be assumed that this process causes a decrease in the rate of liquid rising along the longitudinal capillaries of fluorinated PL fabric. The high water absorption of the fabric proves good sorption properties of PL fabric modified by the direct gas fluorination. The good wetting of the fluorinated fabric is proved by the increase in the water contact angles and the increase in the surface energy of the samples fluorinated with an oxygen-containing gas mixture. We checked whether the destruction and the oxidation of the polymer macromolecules [7,13], have not a negative effect on the tensile strength and elongation at break of the PL sewing thread and fabric. The data are presented in Tables 5 and 6, respectively. It follows from the tables that fluorination leads to some decrease in the tensile strength and elongation at break of the PL materials. After fluorination of the PL sewing thread the decrease in tensile strength is stronger. Apparently, this is due to the high anisotropy of the structure of highly twisted PL sewing threads. This assumption is confirmed by a high variation coefficient for the ultimate tensile strength and the elongation at break of the PL sewing threads. The tensile strength and
,
where dsol is the dispersion component of the surface energy of a solid, liq sol d is the dispersion component of the surface energy of a liquid, p is the polar component of the surface energy of a solid,
liq p
is the polar
component of the surface energy of a liquid, and is the surface energy of a liquid. The unknowns in the equation are the polar and dispersion components of the surface energy of the solid ( dsol , psol ). When solving the system of equations, we obtained their values and the value of the surface energy of the solid phase: sol = dsol + psol . We determined the values of the total surface energy, its polar and dispersion components for the PL film, fluorinated under various conditions. We also estimated the effect of the duration of holding of the modified film in the air to the surface energy of the film and its components. The results are shown in Fig. 2. As can be seen from Fig. 2, in the fluorination of the PL material the values of its total surface energy and its polar component substantially increase. The dispersion component increases in a les degree. With an increase of the duration of fluoridation from 1 to 3 minutes to 15 min, this tendency is more pronounced. The addition of oxygen into the fluorinating mixture leads to a more significant increase in a surface energy compared to the use of mixtures without oxygen. This effect is associated with a formation of oxygencontaining functional groups on the surface of the polymer, which are characterized by a high surface energy. The trend identified for the PL coincides with the regularities for polypropylene and polyphenylene oxide [8,26] described in the literature. Fig. 2 shows that the PL film is characterized by a maximum high total surface energy immediately after the fluorination with an oxygencontaining mixture. When the fluorinated film is held in air, the total surface energy and its polar component slightly decrease. The dispersion component slightly increases when the film is stored in air. The surface energy is the main factor that determines the wettability of materials. The morphology of the surface has also a significant effect on wettability. The wetting of the surface of a smooth non-porous PL film proceeds in a homogeneous mode. In this case, the liquid contact with the entire surface of the solid and completely fills the hollows on it. As the PL film is hydrophilic (Θ < 90°), increasing the roughness will increase the wettability [27]. To assess how fluorination affects the roughness of the surface of PL materials, we investigated the morphology of the surface of fluorinated PL films by atomic force microscopy. The results are shown in Fig. 3. The figure reflects the visualized understanding of the surface of PL films and profile lines of their surfaces. We characterized the roughness using the root mean square - RMS, maximum (Hmax) and average (Hav) values. These data are presented in Table 2. It follows from the figure and table that the fluorinated PL film has a higher roughness than the untreated film. Consequently, the wettability of such film will be additionally increased. Besides, we can see that when processing with a fluorine-containing mixture without oxygen, a more significant, profound change in the morphology of the surface liq
117
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Fig. 2. The effect on the (a) total surface energy, (b) polar and (c) dispersion components of the surface energy of the PL film, the duration of its fluorination and the time of storage in air. 1 - untreated film; 2, 2', 2” - fluorination with a gas mixture (10 % F2 + 90% N2); 3, 3', 3” - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2). Duration of fluoridation: circle - 1 min.; triangle - 3 min.; square - 15 min.
elongation at break of the PL fabric after fluorination decrease slightly. The use of an oxygen-containing gas mixture for the fluorination of PL fibrous materials leads to a higher loss of the tensile strength. This is due to the low resistance of polyethylene terephthalate to the effects of oxidation. Thus, the maximum decrease in tensile strength of the fabric after fluorination is about 10%, the decrease in tensile strength of thread is about 15%. This decrease in strength is small, while the use of chemical and plasma methods of increasing hydrophilicity leads to a decrease in the strength of PL fabric by 30–40% [3–6]. In [19] we showed that a polypropylene fibrous material at the direct gas fluorination acquires the ability to inhibit the vital activity of either pathogenic bacteria or microfungi, depending on the composition of the gas mixture. In this paper we evaluated the effect of direct fluorination on the barrier antimicrobial properties of the PL fibrous material. Table 7 presents data about growth or inhibition of typical test cultures in contact with fluorinated PL fabric: Staphylococcus aureus and Escherichia coli strain M-17 - respectively gram-positive and gram -negative bacterial cultures, Candida albicans - yeast-like microscopic fungi. It follows from the table that as a result of fluorination the PL fabric acquires barrier antibacterial properties. They are weakly expressed after fluorination with a gas mixture without oxygen. The PL fabric acquires a sufficiently high antibacterial activity when treated with an oxygen-containing gas mixture. PL fabric after fluorination does not
have anti-fungal properties. The cause of the antibacterial action of the fluorinated surface of the PL fabric is apparently, a toxic effect on pathogenic microorganisms occurs when they come into direct contact with the surface of the modified material. The biochemical mechanism of the barrier antimicrobial action of fluorinated PL fabrics requires additional study. 4. Conclusions We have established that the fluorination of PL fibrous materials by a periodic method at room temperature and a pressure of 0.001 0.002 MPa with gas mixtures containing 10% fluorine leads to a significant change in the surface energy of the polymer material. Addition into the fluorinating mixture of 10% of oxygen leads to the formation on the surface of the PL material of an additional amount of oxygencontaining groups that provide an increase in the surface energy of the fiber and its wettability. As a result of fluorination the water absorption of the PL fiber material increases substantially. The maximum increase in water absorption (by 26%) is achieved using an oxygen-containing mixture for fluorination. In spite of increase of the number of oxygen-containing groups on the modified fibers, the rate of water rise along the longitudinal capillaries of the fabric slightly reduced. This is due to the adsorption of water molecules on the additional formed functional groups. The specific surface area of the PL fabric, as well as the size of inter-fiber capillaries, practically does not change. 118
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Fig. 3. Morphology of the PL film (1) and surface profiles (2): а - untreated; b - fluorination with a gas mixture (10% F2 + 90% N2) during 15 min.; c - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 15 min. Method of atomic force microscopy.
Table 2 Roughness characteristics of fluorinated PL films. Fluorinating mixture and treatment duration
RMS, nm
Hmax, nm
Hav, нм
Untreated PL film Gas mixture (10 % F2 + 90 % N2), 15 min. Gas mixture (10 % F2 + 80 % N2 + 10 % O2), 15 min.
2.1 ± 0.4 6.5 ± 1.3 3,5 ± 0,7
28.9 ± 1.3 76.9 ± 5.8 58.5 ± 2.8
13.1 ± 0.5 30.4 ± 2.9 22.9 ± 1.2
119
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Fig. 4. Fluorine mapping of PL fabric after fluorination within 15 min. Gas mixture: a - (10% F2 + 90% N2); b - (10% F2 + 80% N2 + 10% O2). EDX method. Table 3 Water absorption of a PL fabric modified by the direct fluorination at a total pressure of the gas mixture of 0.002 Mpa. Fluorinating mixture and treatment duration
Water absorption, %
Untreated PL fabric Gas mixture (10 % F2 Gas mixture (10 % F2 Gas mixture (10 % F2 Gas mixture (10 % F2
49.5 52.6 56.0 57.9 62.3
+ + + +
90 90 80 80
% % % %
N2), 3 min. N2), 15 min. N2 + 10 % O2), 3 min. N2 + 10 % O2), 15 min.
± ± ± ± ±
1.5 1.6 1.8 1.7 1.9
The tensile strength of the PL fabric after fluorination changes insignificantly. As a result of fluorination the PL fabric acquires barrier antibacterial properties. They are weakly expressed in the case of fluorination of the PL fabric with a gas mixture without oxygen and are sufficiently high when the PL fabric treated with an oxygen-containing gas mixture. Modified by direct fluorination PL fibrous material with improved wettability and high water adsorption can be used to produce a wide range of household products, upholstery materials and materials for the interior of vehicles.
Fig. 6. Isotherm of nitrogen adsorption by PL fabric, fluorinated with gas mixture (10% F2 + 90% N2) during 15 min. at a total pressure of the mixture 0.002 Mpa.
Fig. 5. Dependence of the liquid rise height by the warp (a) and by the weft (b) on the duration of the raising of the liquid for the PL fabric: 1 - untreated; 2 fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 3 min.; 3 - fluorination with a gas mixture (10% F2 + 80% N2 + 10% O2) during 15 min. It follows from the figure that the rate of water rising along the longitudinal capillaries of the fabric decreases as a result of fluorination.
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Table 4 The specific surface area and the size of inter-fiber capillaries of the PL fabric modified by the direct fluorination at a total pressure of the gas mixture 0.002 MPa (method of capillary condensation of nitrogen). VALUE
Fluorinating mixture and treatment duration
Specific surface area, m2 / g Inter-fiber capillaries volume, cm3 / g Diameter of inter-fiber capillaries, nm
UNTREATED PL FABRIC
GAS MIXTURE (10 % F2 + 90 % N2), 15 min.
GAS MIXTURE (10 % F2 + 80 % N2 + 10 % O2), 15 min.
10.541 0.016 3.176
10.333 0.017 3.170
10.821 0.017 3.173
Table 5 The fluorination conditions influence on tensile strength and elongation at break of PL sewing thread. Fluorinating mixture and treatment duration
Ultimate tensile strength, MPa (cN/tex)
Variation coefficient for the ultimate tensile strength, %
Elongation at break, %
Variation coefficient for the elongation at break, %
Untreated PL sewing thread Gas mixture (10 % F2 + 80 % N2 + 10 % O2) 3 min. 15 min. Gas mixture (10 % F2 + 90 % N2) 3 min. 15 min.
39.0 ± 1.6
5.7
25.6 ± 0.7
3.7
25.3 ± 1.8 22.9 ± 2.0
10.0 12.3
22.0 ± 0.6 21.8 ± 1.1
4.0 7.0
26.8 ± 3.6 26.2 ± 2.7
14.6 18.8
25.3 ± 1.8 22.8 ± 0.9
5.4 10.1
Table 6 The fluorination conditions influence on tensile strength and elongation at break of PL fabric. Fluorinating mixture and treatment duration
Tensile strength, N
Variation coefficient for the tensile strength, %
Elongation at break, %
Variation coefficient for the elongation at break, %
Untreated PL fabric Gas mixture (10 % F2 + 80 % N2 + 10 % O2) 3 min. 15 min. Gas mixture (10 % F2 + 90 % N2) 3 min. 15 min.
366.4 ± 25.6
7.0
27.5 ± 1.1
3.3
332.6 ± 11.6 328.1 ± 24.3
3.5 5.4
23.5 ± 1.7 22.7 ± 0.8
5.8 3.0
352.5 ± 8.1 333.6 ± 13.3
2.3 4.1
24.3 ± 1.3 24.2 ± 1.9
4.4 6.2
Growth (+) or inhibition (-) of test pathogenic microorganisms,%
of Chemistry and Technology), O.Yu. Kuznetsov (Ivanovo State Medical Academy). The work was carried out using the equipment of the Centre for joint use of scientific equipment “The upper Volga region centre of physical and chemical research”.
bacteria
References
Table 7 The effect of fluorination on the barrier antimicrobial properties of PL fabric. Fluorinating mixture and treatment duration
Untreated PL fabric Gas mixture (10 % F2 + 80 % N2 + 10 % O2), 15 min. Gas mixture (10 % F2 + 90 % N2), 15 min.
microfungi Candida albicans
Escherichia coli
Staphylococcus aurous
0 −50
0 −90
0 +47
−28
−6
0
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Acknowledgements The work was carried out within the framework of the state contract with FASO of Russia № 01201260484. In the implementation of the study participated A.P. Kharitonov (Institute of Energy Problems of Chemical Physics (Division), Russian Academy of Sciences). The authors also thank for the participation in the experimental work A.S. Kraev, V.A. Istratkin (G.A. Krestov Institute of Solution Chemistry of Russian Academy of Science), I.V. Kholodkov (Ivanovo State University 121
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