Studies of structure and water vapor transport properties of shape memory segmented polyurethanes for breathable textiles

Shape memory polyurethanes (SMPU) have segmented structure which is capable of changing their shape upon application of heat. Large change of thermomechanical properties would occur across the glass transition temperature (Tg) or soft segment crystal melting temperature (Tms) of SMPU. In addition to the change of thermomechanical properties of SMPU, it also has large change in moisture vapor permeability above and below the Tg/Tms , which would be suitable for smart breathable textile applications. Segmented polyurethanes (SPU) with well defined architectures were synthesized and their structure, shape memory and water vapor transport properties were investigated in this study. From the experimental results and discussion, it was observed that the microstructures, thermo-mechanical properties and shape memory effect of segmented polyurethanes would be altered by segmental architecture. Water vapor transport (WVT) properties of shape memory segmented polyurethanes were confluenced by the polyol structure, soft segment crystal melting, and hydrophilicity.; Selected SPUs were applied to the cotton fabrics by coating method. Water pressure resistance value of 24.5 mbar was achieved for the coated fabric with PTMG (Mn 2900) based SPU containing 15 wt% of PEG (M n 3400). Coated fabrics also maintained good water vapor permeability, therefore confirmed the physiological comfort to the wearer. MWNT reinforced SPU coated fabrics show excellent UV blocking properties. With only 1 wt% of MWNT in the SPU, the UV protection factor (UPF) was about 125 (rated as excellent, >+50) achieved as compared to the uncoated fabric having UPF of 5.6 which is non rate able.; Systematic study on structure and water vapor transport properties presented in this thesis throws light to the polymer chemist to develop smart polyurethane membrane through molecular design from wide range of raw materials available for polyurethane synthesis.