Free volume and the physico-mechanical behaviour of polyurethane/polyacrylonitrile interpenetrating polymer networks: positron annihilation results

A series of semi-interpenetrating polymer networks (SIPNs) of polyurethane (PU) and polyacrylonitrile (PAN) in the weight ratios 90/10, 70/30, 60/40 and 50/50 PU/PAN were prepared using polyethylene glycol, 4,4'-diphenylmethane diisocyanate and acrylonitrile by sequential polymerization. Differential scanning calorimetry and scanning electron microscopy techniques were used to find the glass transition temperature and surface morphology of SIPNs. The tough and transparent SIPN films were characterized for physico-mechanical properties such as density, surface hardness and tensile properties. Positron annihilation lifetime spectroscopy (PALS) was used to measure the free volume behaviour of the IPNs. The sorption behaviour of IPNs with benzene penetrant was also measured. An attempt was made to correlate the PALS results with the mechanical and sorption properties of the SIPNs. (c) 2005 Society of Chemical Industry.