Journal of Membrane Science 274 (2006) 219–226 Structural characterization and mass transfer properties of nonporous segmented polyurethane membrane: Influence of hydrophilic and carboxylic group S. Mondal ∗ , J.L. Hu Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China Received 2 May 2005; received in revised form 14 August 2005; accepted 19 August 2005 Available online 9 November 2005 Abstract An attempt has been made to investigate the influence of hydrophilic and carboxylic groups on structure and mass transfer properties of polypropylene glycol (number average molecular weight of 1000 g mol -1 , PPG 1000) based segmented polyurethane (SPU). Polyethylene glycol (number average molecular weight of 3400 g mol -1 , PEG 3400) (hydrophilic segment) or dimethylol propionic acid (DMPA) (carboxylic group) or combination of PEG 3400 and DMPA were used to modify the SPU. For comparison, SPU without hydrophilic/carboxylic group was also synthesized. Structures were investigated by Fourier-transform infrared (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and tensile tester. Mass transfer properties were investigated by equilibrium sorption and water vapor permeability measurements. FT-IR spectra of C O stretching was indicated that with the introduction of hydrophilic or acid groups in the polymer backbone, the hydrogen bonding of urethane groups were became weaker or stronger respectively. Nearly amorphous structures of all SPU samples were evidenced by WAXD and DSC results. The presence of DMPA increases the interaction between the polymer chains, which increases the glass transition temperature (T g ) and make the polymer tough. In contrast flexible PEG 3400 segment decreases the T g and increases the percent strain at maximum load. Experimental results revealed that the mass transfer properties not only influenced by amorphous region but also on the interaction between the polymer chains. Presence of hydrophilic group enhances the sorption as well as water vapor permeability (WVP). Abrupt changes of mass transfer properties were observed for SPU with PEG 3400 due the presence of more polar group and longer flexible chains of PEG 3400 which will originates holes in the polymer membranes. The membrane with DMPA content, lowest permeabilities was characterized by a higher degree of physical cross-linking imposed by carboxylic functionality. © 2005 Elsevier B.V. All rights reserved. Keywords: Hydrophilic group; Carboxylic group; Ionic interaction; Mass transfer 1. Introduction Water- and windproof garments which are permeable to water vapor and perspiration have been on the market for over 15 years [1]. These breathable and therefore functional cloth- ing are gaining more market segments in apparel wear. The range includes high-tech garments for professional athletes as well as casual wear. Highly sophisticated high-tech membranes are used to produce laminates, which are then treated by the clothing industry to make high-tech clothing for special pro- ∗ Corresponding author at: C/O Mr. Naba Kumar Mondal, Vill & P.O., Debi Parulia, Dist. Birbhum 731244, West Bengal, India. Tel.: +91 3484 280623/+852 2766 6524; fax: +852 2773 1432. E-mail address: subratamondal@yahoo.com (S. Mondal). fessional groups like firemen, postmen or the military. Several characteristics would make segmented polyurethane especially suited for the use in waterproof and breathable fabric [2]. Their flexibility, especially at low temperatures, yields a soft hand. The materials would maintain good barrier properties while providing high breathability, a combination of attributes would be required by the outdoor and performance sportswear industries. In the application of water proof textiles, the temperature dependency of water vapor permeability is an important fac- tor to be considered for the effective utilization of the materials [3]. A well known method to produce water proof breathable fabrics is to coat/laminate a microporous polyurethane film pre- pared by wet process on a fabric surface. Microporous laminates would be breaths due to their permanent, air-permeable pore 0376-7388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2005.08.016