Waterproof breathable coatings

Table 6.8 shows the potential applications of biopolymers or their derivatives in imparting other functional properties such as insect-repellent, waterproof/breathable coating, hand building, easy care finishing/hand building to the treated cotton-containing fabrics. 

Waterproof breathable coating AATCC 127-1977 on a Shirley hydrostatic-head tester Resistance to water penetration... 

Palankkumaran, M., Agrawal, A. K., and Jassal, M. (2008). Waterproof breathable coating based on poly (vinyl alcohol) for cellulosic fabric. I. Ind Text. 38,151-166. 

With respect to sustainability and waste management, the implementation of human-made, biodegradable polymers in textile coating is also examined. Palanikkumaran et al. (2008) developed waterproof breathable coatings based on polyvinyl alcohol for cotton fabrics. 

Another distinct development of smart breathable fabric is based on biomimetics. Biomimetics is the mimicking of biological mechanisms, with modification, to produce useful artificial items. The water vapour permeability of fabric coatings can be improved by incorporating an analogue of the leaf stomata which open when the plant needs to increase moisture vapour transpiration and close when it needs to reduce it. Currently, there are several developments in the area of waterproof breathable fabrics based on biomimetics, as discussed below. 

Painter CJ. Waterproof, breathable fabric laminates a perspective from film to market place. / Coated Fabrics 1996 26(2) 107-30. 

Kannekens A. Breathable coatings and laminates. J Coated Fabrics 1994 24(l) 51-9. Holmes DA, Grundy C, Rowe HD. The characteristics of waterproof breathable fabric. J Cloth Tech Manag 1995 12(3) 142. 

Holmes DA (2000), Performance characteristics of waterproof breathable fabrics,/ournaZ of Coated Fabrics, 29(4), pp. 306-316. 

Kang et al. first used direct electrospinning of PU onto the substrate fabrics (polyester/nylon blended fabric, which contained stainless steel yarn in weft) to prepare the waterproof-breathable fabric. PU was solvent electrospun onto the substrate fabric to develop the waterproof-breathable fabric with lightweight and thermal insulation [22], The reported air permeability and WVT rate were 0.5 cm /cm /sec and 375.80 g/h/m, respectively, for electrospun PU coated fabric, which were far better than the PU coated fabrics. Lee et al. developed electrospun PU layered fabric systems in which nanofibrous web was layered on spunbonded nonwoven to check the possibility of developing protective clothing materials as barriers to liquid diffusion (Fig. 14.2a-c). Layered clothing systems with electrospun... 

Waterproof Finishes. Waterproofing results from coating a fabric and filling the pores with film-forming material such as varnish, mbber, nitroceUulose, wax, tar, or plastic. The materials may be appHed as hot melts, eg, waxes or some polymers, as solvent solutions, or as aqueous latexes. The continuity of the film provides the water resistance. Except for tents, tarpauHns, and covers, coated fabrics have been largely replaced by plastics, and by fabrics treated with water and oU repeUents that do not reduce permeabUity to air and water vapor. Eabrics are also commonly laminated to films, such that the total stmeture is waterproof (15), or in some cases water-resistant but breathable (16). 

The main property of the outer shell is to provide a protection against the outside weather conditions, mainly rain, snow and wind. In order to avoid excessive sweat accumulation, the outer layer should allow moisture transfer from the body to the environment. Such waterproof, windproof and breathable fabrics (WBF—mainly membranes and coatings) have been on the market for more than 30 years. The waterproof properties and, at the same time, the water vapour transfer are either achieved with a micro-porous or a hydrophilic structure, or a combination of both technologies (bi-component WBF). Waterproofness and breathability are contradictory requirements and, therefore, a compromise has to be found between protection and comfort properties. This compromise is usually achieved by adapting the porosity and thickness of such WBF layers. 

Recent research has demonstrated that electrospun membranes possessed excellent barrier performance against toxins in aerosol form and maintained high WVT simultaneously. Electrospun nanoflber-coated nonwoven fabrics remarkably blocked liquid pesticide penetration through the materials which make them practically more desirable as compared to the conventional fabrics and porous coatings (Fig. 14.1). The aim of this chapter is then to give a detailed overview of recent advances in the application of breathable and waterproof, chemical and antimicrobial, and radiation protective materials fabricated from electtospinning. 

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