A large number of interpenetrating polymer networks (IPNs) based on polyurethane of castor oil and isophorone diisocyanate with cardanyl methacrylate and its homopolymer were synthesized using benzoyl peroxide (BPO) as initiator and ethyleneglycol-dimethacrylate (EGDM) as cross-linking agent. The solvent absorptivity behaviour of different IPNs have been studied. The thermal properties have been studied and the kinetic parameters involved in the thermal degradation of the IPNs have been evaluated by using the computerised LOTUS package method.