Agricultural wastes and natural oils have taken the priorities as raw materials for synthesis of polymers over the traditional petrochemical based raw materials. Interpenetrating Polymer Networks based on polyurethane of polyol modified linseed oil and 1,6-diisocyanatohexane with phosphorylated cardanol using benzoyl peroxide as initiator and ethylene glycol dimethacrylate as crosslinker were synthesized. The chemical structures of these polymers were confirmed by Fourier Transform Infrared Spectra. Various Thermal Analysis techniques were used to determine the percentage of decomposition of such polymer blends at the interval of 50O celsius , ascertain the relative thermal stability of the polymers, evaluate temperatures of maximum rate of decomposition and study the exothermic and endothermic behavior of associated with decomposition process. Kinetic constants, order of reaction and energy of activation, were calculated at two different temperature ranges for the thermal degradation of polymers by the dynamic Freeman-Anderson method. It was observed that the relative thermal stability of such biopolymers not only depends on the NCO/OH molar ratio of the polyurethane component but also depends on the PU/PC weight ratio of the Interpenetrating Polymer Networks. The calculated kinetic parameters were also in good tune with observed thermal data. Surface morphology was studied by X-ray diffraction analysis and scanning electron microscopy. It was observed that the variation of NCO/OH molar ratio and PU/PC weight ratio has appreciable effect on the crysrtallinty and surface morphology of the polymers.