Structure-thermal property relationships for polycyanurate-polyurethane linked interpenetrating polymer networks

Chemical structure and thermal-oxidative degradation of sequential IPNs based on crosslinked polyurethane (CPU) and poly-cyanurate network (PCN) have been studied. As a result of chemical interaction between monomer, dicyanate ester of bisphenol A (DCEBA) and CPU during PCN formation (polycyclotrimerization of DCEBA into CPU matrix), covalent bonding between the networks occurs, leading to creation of linked IPNs (LIPNs). The formation of a new hybrid network (HN) structure has been confirmed. The coexistence of CPU, PCN and HN structures in the LIPNs, confirmed by infrared spectroscopy and by the observation of degradation stages characteristic for each structure, depends on the ratio of the components. Three structures were found for the 90/10 CPU/PCN; HN and PCN were observed in the 70/30 LIPN and the hybrid network was the main structure detected for the 50150 LIPN. (C) 2002 Elsevier Science Ltd. All rights reserved.