Physiochemical Studies of PMR Resins. II: Mechanism and Kinetics of Reactions Occurring in the Temperature Range 50°C-315°C

We have studied the amidizaton and imidization reactions in PMI prepolymers in the temperature range of 50°C-315°C by using a commercial cure cycle. The results in this temperature range, obtained with model compounds simulating the different reactions occurring in a PMR resin, indicate that there are competing side reactions leading to highly varied chemical groups, such as imide-amide and anhydride-amine, which may cause degradation of the final properties of the material as a result of the heterogeneity of the medium. A study of the rearrangement and cross-linking reactions has shown that several mechanisms may be involved, depending on whether the systems are in the molten or solid states. The results obtained can be applied to the study of commercial prepregs.