CURE KINETICS OFAPHENYLETHYNYL-TERMINATED PMDA-TYPE POLYIMIDE IN THE POLYMERIZATION OF MONOMERIC REACTANTS (PMR) PROCESS

摘要

Aromatic polyimide matrix composites exhibit high glass transition temperatures, wide processing windows, and suitable thermal oxidative stability. However, a major limitation of polyimide resins is low toughness, which can lead to (premature) brittle failure. Recently, a phenylethynyl- terminated PMDA-type polyimide, based on a KAPTON backbone structure in PMR process, was developed. This high-temperature polymer exhibits much greater elongation-to-break compared to existing polyimide systems. The objective of this study was to determine the kinetics of imidization and crosslinking in this polyimide resin, and to determine rates of reaction as a function of basic process parameters (temperature, time, etc.). In this work, we used differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) to identify the temperature range for imidization and cure. TGA was also used to track weight loss during imidization. We estimated a degree of imidization and developed a two-stage, first-order kinetic model to describe and predict imidization. In addition, we developed a first-order kinetic model to similarly describe the crosslinking reaction. Such models can be used to optimize cure procedures, allowing users to improve productivity and part quality while reducing cost.