Mechanical properties of simultaneous interpenetrating polymer networks of Castor oil based polyurethane and polystyrene

Castor oil and 4,4'-diphenyl methane diisocyanate based polyurethane (PU)-polystyrene (PS) simultaneous interpenetrating polymer networks (IPNs) were synthesized with various PU/PS ratios (100/0, 90/10, 80/20, 75/25, 60/40 and 50/50). Mechanical properties (tensile strength, % elongation, elastic modulus, wear resistance, tear resistance and Shore-A hardness) of the IPNs showed a significant improvement beyond a critical styrene level (25% by weight). However, % elongation at break showed a maximum at 40% styrene. PU/PS IPNs of a fixed styrene level with varying amounts of styrene crosslinking agent, divinyl benzene (DVB), were also synthesized. These materials showed a significant improvement in the mechanical properties with increasing concentration of DVB. The observed behaviour is explained on the basis of results from swelling and Soxhlet extraction studies. (C) 1997 Elsevier Science Ltd.