Sorption and diffusion of organic solvents through interpenetrating polymer networks (IPNs) based on polyurethane and unsaturated polyester

The equilibrium swelling experiments of interpenetrating polymer networks ( IPNs) based on castor oil based polyurethanes (PU) and unsaturated polyeste r (UPE) were performed in various solvents, in order to calculate their sol ubility parameter. The kinetics of swelling and sorption have also been stu died in chlorobenzene at 25 degrees C. IPNs with various weight composition of PU and UPE (80:20, 50:50, 20:80), and also having various crosslink den sity (NCO/OH ratio) viz. 1.2, 1.5 and 2.0 were employed in the study. The r esults are found to vary with the weight composition of the components and crosslink density of the samples. The sorption behavior is also found to va ry with the hydroxyl number (molecular weight) of the polyol employed in th e preparation of PU. Studies revealed that, the sorption is anomalous in na ture in all the cases. Diffusion coefficient (D is found to increase with b oth increase in NCO/OH ratio and UPE content, whereas sorption coefficient (S) shows a reverse trend in all the samples studied. From the swelling stu dies, the molecular weight between two crosslinks (M-c) and hence the numbe r of chains per unit volume(-)(N) and degree of crosslinking (v) were also calculated. The results obtained were compared with that of the homopolymer networks. (C) 2000 Elsevier Science Ltd. All rights reserved.