Water vapor permeability and mechanical properties of fabrics coated with shape-memory polyurethane

Water vapor permeable fabrics were prepared by coating shape-memory polyurethane (PU), which was synthesized from poly(tetramethylene glycol), 4,4'-methylene bis(phenylisocyanate), and 1,4-butanediol, onto polyester woven fabrics. Water vapor permeability and mechanical properties were investigated as a function of PU hard-segment content or polymer concentration of the coating solution. Water vapor permeability of PU-coated fabrics decreased dramatically with increased concentration of coating solution, whereas only a slight change was observed with the control of PU hard-segment content. The coated fabric showed the clear appearance of a nonporous PU surface according to SEM measurements. Attainment of high water permeability in PU-coated fabrics is considered to arise from the smart permeability characteristics of PU. Mechanical properties of coated fabrics, although there was some variation depending on the concentration of coating solution, were primarily affected by PU hard-segment content. Fabrics coated with PU hard-segment content of 40% showed the lowest breaking stress and modulus as well as the highest breaking elongation, which could be interpreted in terms of the dependency of mechanical properties of coated fabrics on PU hard-segment content and the yarn mobility arising from a difference in penetrating degree of coating solution into the fabric. (C) 2004 Wiley Periodicals, Inc.