Theoretical investigation on thermal aging mechanism and the aging effect on mechanical properties of HTPB-IPDI polyurethane

The CO bond connected directly with CH2 moiety is the weakest bond. The half-life time of the cleavage of CO bond exhibits a temperature dependent exponential decay function, which shows clearly that the thermal-aging of HTPB-IPDI is accelerated with increased temperature. The MD simulations show that the aged HTPB-IPDI densities decrease when the carbon dioxide formed during thermal aging disperses inside the cell or diffuses out of the system. The decreased tensile modulus and shear modulus is attributed to the dissociation of hard segments and breaking of hydrogen bonds in HTPB-IPDI cross-linking network.221