Sorption behaviour of interpenetrating polymer networks based on polyurethane and unsaturated polyester

Kinetics of swelling and sorption behaviour of interpenetrating polymer networks (IPNs) based on castor-oil-based polyurethanes (PU) and unsaturated polyester (UPE) in chlorobenzene has been studied at 25 degrees C. IPNs having different weight composition of PU and UPE and also having various crosslink density (NCO/OH ratio) were employed. Effect of hydroxyl number (molecular weight) of polyols on the sorption behaviour has also been investigated. All the results obtained were compared with that of the homopolymer networks. Studies revealed that the sorption is anomalous in nature in all the samples. Diffusion coefficient is found to increase with both increase in NCO/OH ratio and PE content in the IPNs, whereas sorption coefficient shows a reverse trend. The swelling results have been used to calculate the molecular weight between two crosslinks (A,) and hence the number of chains per unit volume (N) and degree of crosslinking (v) in all the samples studied. (C) 1998 Elsevier Science Ltd. All rights reserved.