Improved abrasion resistance of textile fabrics due to polymer coatings

Abstract

Textile fabrics are often subject to abrasion, starting from exposed parts of garments to a variety of technical textiles. Abrasion protection by usual coatings, however, can significantly decrease the water vapor transport through a fabric which is often not desired, especially in the case of garments. In our paper, we report on an approach to combine increased abrasion resistance with sufficient water vapor transport properties. For this, different polymers (poly(methyl methacrylate), acrylonitrile butadiene styrene, or amorphous polyamides) were coated on cotton and polyester woven fabrics. The results of abrasion tests against sandpaper show significantly increased abrasion resistance. The absolute evaporation resistance, measured by a Permetest testing device, was only slightly increased up to values still acceptable for typical garments. Images of all coatings by helium ion microscopy deliver an explanation for the measuring results. Polymer coatings on the polyester fabric resulted in a slight reduction of the hydrophobicity, while coating the cotton fabric severely increased the contact angles of the originally superhydrophilic material.

Keywords

Coated fabrics engineered textiles materials measurement protective fabrics technical textiles

Introduction

Abrasion resistant textile fabrics are desired for applications in garments, especially for protective clothing or work-wear, as well as for several technical textiles. Several approaches are described in the literature to reach this goal, amongst which only few ideas deal with the yarn or fabric construction. The weave of different two-layer woven fabrics could be shown to modify the abrasion resistance as well as the finishing process of the cotton/linen fabrics [1]. Slub yarns for upholstery fabrics were modified with respect to slub length, distance and thickness as well as yarn linear density to improve the abrasion resistance of the resulting woven fabric [2].

Chemical methods include, e.g., finishing a nylon fabric with poly(acrylic acid) and trichloromethylsilane, resulting in abrasion-resistant superhydrophobic textile surfaces [3]. Kevlar textile fabrics were coated with silver nanocluster/silica composite layers of different thickness to increase antibacterial properties and abrasion resistance at the same time [4]. Especially for warp yarns before weaving, PVA (polyvinyl alcohol) is an often used sizing agent which also increases the abrasion resistance of cotton yarns [5]. Due to its missing biodegradability, tests were performed to replace PVA by soymeal [6]. Loading polyester fabrics with TiO₂ nanoparticles in a high-temperature pressure exhaustion process could increase washing and abrasion resistance of the fabrics, in addition to the main aim of self-cleaning properties [7]. Including nanosilver particles in the spinning process, the abrasion resistance of weft-knitted samples could be increased by a factor of 3 [8]. Using a sol–gel coating, abrasion resistance and water-repellency of silk fabrics could be increased at the same time [9]. Spider silk, on the other hand, was used to increase the abrasion resistance of natural and man-made furniture textiles [10].

A combined hexafluoropropane plasma treatment could increase the abrasion resistance of cotton woven fabrics by approx. 5% [11]. Superhydrophobic surfaces were created by coating diverse materials with nanoparticles and vinyltriethoxysilane, showing a certain abrasion resistance of the coating, with the exception of textile fabrics after abrasion against sandpaper [12]. Superamphiphobic cotton fabrics with high abrasion resistance of the coating were gained by depositing organically modified silica alcogel particles on chitosan-coated cotton fabric and binding the coating with perfluorooctyltrimethoxysilane [13]. On the other hand, superamphiphobic coatings based on photo-polymerization of hybrid thiol-ene resins with hydrophobic silica nanoparticles and perfluorinated thiols showed a good mechanical durability in sandpaper abrasion tests [14]. Compressive shrinkage of cotton fabrics was found to increase the abrasion resistance in comparison with the original fabrics [15]. Using a sol–gel approach, abrasion resistance, anti-pilling effect, antibacterial and fungicide properties were obtained using (3-glycidoxypropyl)trimethoxysilane and aluminum isopropoxide combined with bioactive nanoparticles [16]. A sol–gel method was also used to coat cotton fabrics with hybrid SiO₂/Al₂O₃ sols synthesized from (3-glycidoxypropyl)trimethoxysilane and aluminum isopropoxide as precursors, resulting in five times higher abrasion resistance on cotton [17] and nearly 40% increased abrasion resistance on polyester/cotton woven fabrics [18]. Embedding fluorinated decyl polyhedral oligomeric silsesquioxane and fluorinated alkyl silane in a poly(3,4-ethylenedioxythiophene) (PEDOT) coating prepared to show a certain conductivity did not significantly change the conductivity but severely increased washing and abrasion resistance [19]. With a conductive polypyrrole coating on polyester, however, the abrasion resistance was not significantly modified by coating with different immersion times in the monomer solution [20].

Only few research groups, however, have tested the influence of polymer coatings on textile fabrics for the purpose of abrasion resistance of the fabric itself. Polyurethane (PU) was mist polymerized on a cotton fabric, resulting in a fine polymer layer which was sufficient to double the wearing resistance as compared to the original cotton fabric, while at the same time having only little impact on water vapor transmission and mechanical properties [21]. Coatings with PU and polyvinyl chloride (PVC) were found to withstand a certain number of abrasion cycles until losing their hydrophobic properties [22]. Especially PU is tested for such applications since it is known to show excellent abrasion resistance [23]. 3-glycidoxypropyltriethoxysilane (GPTES) was used to create nanohybrid organic-inorganic coatings on cotton fabrics which did not influence the wear resistance of the treated textile fabrics [24].

Other polymers, especially materials which can be dissolved relatively easily, such as poly(methyl methacrylate) (PMMA), acrylonitrile butadiene styrene (ABS), or amorphous polyamides (PAs), are either ignored so far in the scientific literature (in case of ABS) or not examined in terms of their abrasion resistance properties. The main advantage of such materials is that they can be dissolved in relatively low-toxic solvents, such as acetone or ethanol, while PU necessitates toxic di-isocyanates as precursors. Besides, PU usually forms a closed coating layer, often blocking air and water vapor and making such coatings thus not usable for garments.

This article thus shows first examinations of PMMA, ABS and PA coated on cotton and polyester fabrics with respect to the samples’ abrasion resistance, water vapor permeability and hydrophobicity.

Experimental

The woven fabrics described in Table 1 were chosen for the experiments described here. The polyester used in this study is a polyethylene terephthalate (PET). Linear densities of the yarns are 200 dtex (polyester woven fabric in warp and weft) and 98 dtex (cotton woven fabric in warp and weft), respectively.

Table 1.

Thicknesses, areal weights, warp and weft densities of textile fabrics used for coating.

Material	Thickness/mm	Areal weight/(g/m²)	Warp threads/cm⁻¹	Weft threads/cm⁻¹
Cotton (CO)	0.32	94	30	22
Polyester (PES)	0.55	123	26	25

PMMA and ABS were dissolved in acetone and PA was dissolved in ethanol using mass concentrations of 5% and 10%, respectively. Coating was performed using a revolving doctor with a wet film thickness of 100 µm. After the solvents were applied, the fabrics were dried for 1 h at 55℃.

Helium ion microscopy (HIM) pictures were taken with an Orion Plus (Carl Zeiss) at an acceleration voltage of 35 kV and a current of 0.4 to 0.5 pA. An electron flood gun was used to avoid charging effects during the secondary electron detection.

Abrasion resistance was tested using a linear abrasion tester (sliding block test) according to EN ISO 13427 with sandpaper grain size 400 instead of grain size 100, as described in the standard, to avoid too fast abrasion. In this test, the abrasion tester consists of two parallel smooth plates of dimensions 50 mm × 200 mm, one of which is moved in a reciprocating motion with a maximum of 90 double strokes per minute along a stroke length of (25 ± 1) mm, while the other one is partly fixed and can only move perpendicular to the first one. A weight of 6 kg is applied on the top plate. Five rectangular samples of dimensions 50 mm × 300 mm were prepared and conditioned in standard atmosphere before performing the test.

Water vapor resistance was measured on five samples per data point using a Permetest skin model (built by Sensora Textile Measuring Instruments and Consulting, Czech Republic). The measuring head of this device is covered by a resistant semi-permeable foil, prohibiting liquid water transport from the measurement system to the sample. A sensor measures the cooling flow due to water evaporation from the thin porous layer and evaluates these values to calculate the water vapor permeability and the evaporation resistance [25,26].

Hydrophobicity was evaluated with distilled water at 23℃ using the contact angle measurement device OCA 15 Pro by Dataphysics. This instrument uses a direct dosing system to position liquids with an electronic syringe module on the textile fabric under examination. The droplet is lighted by an LED with software-controlled intensity which automatically compensates temperature drift. Images of the drop are taken by a 6-fold zoom lens with adjustable observation angle. Evaluation of the contact angle is performed automatically by the integrated software. Each contact angle was measured for 10 different droplets.

Results and discussion

The results of the abrasion tests are depicted in Figure 1. The graph shows the abrasion cycles until failure of the fabrics, i.e. until the occurrence of a first damage in the woven fabric. When the fabric was examined for holes, the test was discontinued to avoid exposing it to inhomogeneous shear stress.

Figure 1.

Abrasion cycles until failure of uncoated references and coated fabrics. The y-axis is scaled logarithmically.

Firstly, comparing pure cotton and polyester fabrics (green bars), the latter obviously have a significantly higher abrasion resistance. Direct comparisons between fabrics produced from these materials are scarcely found in the literature; generally, cotton seems to be less abrasion-resistant than polyester [27]. Typically yarn and fabric constructions are reported to have a more severe influence on this property [28]. Coating either fabric with any of the polymers used in this test always increases the abrasion resistance significantly. With regard to polyester, all polymers used with a concentration of 10% resulted in an abrasion resistance against sandpaper grain 400 of at least 5000 cycles; tests were stopped afterwards. Compared with the original value of (225 ± 25) cycles, this is an increase by a factor of more than 20. For the combination of PA on the polyester fabric, this result was also achieved for only 5% concentration, while PMMA and ABS with a concentration of 5% on polyester already resulted in a significantly increased abrasion resistance. For cotton fabrics, the values are generally smaller; however, coating with 5% of any polymer results in an increase of the abrasion resistance by nearly one order of magnitude. Nevertheless, it should be mentioned that there is no linear concentration dependence of the maximum abrasion cycles until failure. This can be explained by the finding that the coated layer thickness on the surface is not mainly influenced by the polymer concentration in the solution, but mostly by the (constant) force on the revolving doctor and the chosen wet film thickness. It can be assumed that coating twice with 5% polymer solution will result in a thicker coating on the surface and thus a higher abrasion resistance than coating once with 10% polymer solution.

On cotton, only PA – which was also superior on polyester – in a concentration of 10% reached an abrasion resistance of at least 5000 cycles. With 10% ABS and PMMA coatings on cotton, however, abrasion resistances of several hundred cycles could be reached which is approx. one order of magnitude higher than the abrasion resistance of the uncoated references ((9 ± 6) cycles). The assumption was that the different results can be attributed to a correlation between abrasion resistance and surface hardness. However, this could not be confirmed by hardness measurements with the polymers used. Shore-D hardness measurements have yielded an average value of 70 for PA, 73 for ABS, and 87 for PMMA on compact sample bodies. This suggests that the adhesion of the coating on the filaments plays a crucial role in the abrasion resistance. The original abrasion resistance of the fabric itself becomes only significant after the coating has been at least partially removed, as can be seen in Figure 2. In the places where the filaments have broken, it is visible that the filaments look rough, indicating that the coating material has been rubbed off the filaments.

Figure 2.

Microscopic images at nominal 200× magnification of the damaged woven fabrics after abrasion tests.

The resulting abrasion resistance is therefore primarily dependent on the adhesion between the fabric and the coating since damaging the coating may either occur by rubbing the coating off completely or by separating it mechanically from the filaments. For future applications and further investigations, a plasma treatment could further increase the impregnation of the filaments and the adhesion between the coating and the substrate.

The impregnation of the fabric with the coating depends on the ratio of the surface energies, the application method, the viscosity of the polymer solution and the morphology of the fabric.

For the smaller concentration, the results of the abrasion tests on cotton are significantly worse; apparently, the higher concentration is necessary to guarantee a certain protection of the cotton fabric against abrasion by sandpaper. On the other hand, cotton is typically used in less harsh environments than polyester, which may be used in technical applications. Thus, more series of tests using abrasives other than sandpaper can be investigated, giving rise to the increase of cotton abrasion resistance for applications such as T-shirts or other garments which are typically abraded at some positions, such as on the shoulders due to heavy backpacks or along the belly due to constant abrasion by the belt-buckle, or on the knees and elbows of work wear.

It should be mentioned that washing the coated fabrics does not greatly affect them; no differences could be detected during the first three washing cycles with heavy duty detergent at 40℃. Future research will focus on investigating a larger number of washing cycles to examine whether the typical washing fastness requirements for garments of 50–100 cycles are met with different washing temperatures and detergents, which ironing temperatures are possible and whether any other care properties are to be considered.

Figures 3 and 4 depict HIM images of all samples under investigation. Due to the use of an flood gun which preserves negative effects of electrical charging, the samples could be investigated without sputter coatings, which might influence the evaluation of the HIM images. It is clearly visible that a higher concentration results in a more continuous coating on the filaments. While the 5% coatings leave mostly separated filaments, the 10% coatings fill in the gaps between the filaments and leave only the fabric pores open. This is another hint towards future tests with multiple coating layers of reduced polymer concentration. Since all used polymers have roughly equal surface energy ratios, there are no great differences in the adhesion between the fabric material and the polymer coating. As can be seen in Figures 3(c), (e) and (g) and 4(c), (e) and (g), even at 10% solvent concentration, there is no agglomeration, but continuous coatings can be found after drying. This is in contrast to PU coatings, which are located on top of the textile fabrics, closing their pores completely [29 –31].

Figure 3.

HIM images of cotton fabric with different polymer coatings with different solution concentrations. HIM: helium ion microscopy.

Figure 4.

HIM Images of polyester fabric with different polymer coatings with different solution concentrations. HIM: helium ion microscopy.

Another important property of textile fabrics used for garments and other diverse applications is their water vapor permeability. Coating textile fabrics with polymers may lead to significantly increased evaporation resistance if the coating is not thin enough to leave the fabric pores open. Figure 5 depicts the absolute evaporation resistances, measured for the original fabrics as well as the coated ones. While the evaporation resistance levels are increased by the coating by approx. 50–100%, comparing the values of coatings with polymer concentrations of 10% with the original fabrics, the received values are not unusually high for garments such as a polo shirt [32], which is similar to the influence of PU coatings with high water permeability on the water vapor resistance of coated textiles fabrics, as reported in Yun et al. [33]. Thus, the coated textile fabrics can still be used for most of the applications of the original fabrics. It should be mentioned that for both ABS and PA coatings, using a solid content of 5% in the solution, the evaporation resistance is nearly unaltered in comparison to the original fabrics. This suggests that these materials are advantageous in terms of water vapor permeability, compared to PMMA. Combined with the results of the abrasion resistance measurements (Figure 1), PA seems to be the preferable coating polymer.

Figure 5.

Evaporation resistance of the original and the coated fabrics determined by the PERMETEST Skin Model [26].

The correlation of solvent concentration and evaporation resistance can be explained by the decreasing porosity of the fabrics as seen in Figures 3 and 4. The higher standard deviation of the samples with 10 % coatings indicates an increasingly inhomogeneous distribution of the fabrics properties, which may in part be due to the manual coating method.

Finally, the hydrophobicity of the original and the coated fabrics was examined. Figure 6 depicts the resulting contact angles. On pure cotton, the droplets were immediately absorbed by the fabric so that no stable static contact angle could be measured; other measurement procedures are not available with the contact angle measurement device used in this study. The very first photographs taken <1 s after setting the droplet on the textile fabric resulted in an initial contact angle of (20 ± 10)°, depending on the exact measurement time. The highest contact angles were achieved on pure polyester. Correspondingly, contact angles of coatings on polyester were always higher than those of the same coatings on cotton. Differences between coatings with concentrations of 5% and 10 % are neither significant, nor are the differences between the coatings on either textile fabric. Typical water contact angles of the polymers are 70–80° for ABS [34], 65–70° for PMMA [35] and approx. 70° for PA [36]. Since these values are quite similar, it is clear that the values measured here are also relatively independent from the used polymer. While the contact angles measured for coatings on cotton are similar to those found in the literature, the values detected for the PES coatings are clearly influenced by the hydrophobic properties of the textile fabric.

Figure 6.

Contact angles of the original and the coated fabrics.

As the HIM images suggest, the differences in contact angle values are most likely not due to a change in surface energy, but to a change in surface topology. Especially for cotton of which the hydrophilicity was significantly reduced, this fact must be taken into account and may make these polymer coatings unsuitable for some applications. This problem, however, can be solved by using less hydrophobic polymers or hydrophilizing them, if necessary.

Since all three coating materials behave similarly in terms of hydrophobicity of the coated textiles, the aforementioned finding that PA seems to be the favorable polymer for abrasion-resistant, water vapor permeable coatings remain valid.

Conclusion

The influence of different polymer coatings (ABS, PMMA, and PA) on the abrasion resistance, water vapor resistance and hydrophobicity of cotton and polyester woven fabrics was examined. All coatings resulted in an increase of the abrasion resistance by at least approx. one order of magnitude; in several coated fabrics, tests were stopped after 5000 cycles without damage of the fabric. For all coatings, this effect was combined with an acceptable decrease of the water vapor permeability of less than 50% and contact angles between approx. 75°–95°, similar to the original contact angles on the polyester fabrics. These results underline the possibility of creating highly abrasion resistant textile fabrics which nevertheless can maintain their desired water vapor permeability, allowing for applications in protective clothes, work-wear or diverse technical textiles. Furthermore, this shows the general possibility of applying a wide variety of amorphous thermoplastic polymers such as polystyrene, polycarbonate, PVC, polylactides or styrene-acrylonitrile from non-toxic solvents to woven fabrics. The results shown can also be transferred to many other thermoplastic polymers that may be important for specific future applications.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The study was partly funded by the Ministry of Culture and Science of the German State of North Rhine-Westphalia and by the Erasmus+ program of the European Union.

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