Interpenetration Networked Polyimide–Epoxy Copolymer under Kinetic and Thermodynamic Control for Anticorrosion Coating

Abstract

Epoxy (EP) was copolymerized with polyamic acid (PAA, precursor of polyimide (PI)) with termanil monomers of (1) 4,4′-Oxydianiline (ODA) and (2) pyromellitic dianhydride (PMDA) individually to form (PI-O-EP) and (PI-P-EP) copolymers. The FTIR spectrum of PI-O-EP copolymerization intermediates shows that some amide-EP linkages were formed at low temperature and were broken at higher temperature; in additoin, the released amide was available for subsequent imidization to form PI. The curing and imidization of the amide groups on PAA were determined by reaction temperature (kinetic vs. thermodynamic control). In PI-P-EP, the released amide group was very short-lived (fast imidization) and was not observed on FTIR spectra. Formation and breakage of the amide-EP linkages is the key step for EP homopolymerization and formation of the interpenetration network. PI contributed in improving thermal durability and mechanical strength without compromising EP’s adhesion strength. Microphase separations were minimal at PI content less than 10 wt%. The copolymerization reaction in this study followed the “kinetic vs. thermodynamic control” principle. The copolymer has high potential for application in the field of higher-temperature anticorrosion.

Cure Kinetics and Thermal Decomposition Behavior of Novel Phenylacetylene-Capped Polyimide Resins

“…Therefore, the curing mechanism and thermal stability of phenylacetylene-capped polyimide resin have always been the focus of research, which has attracted the extensive attention of many scholars. Chen et al measured the curing reaction process of amide groups on the PI precursor PAA by the reaction temperature and analyzed the formation of a cured product network by FTIR [13]. Qian et al used a compound catalyst of isopropyl peroxide and cobalt naphthalene to optimize the curing temperature of phenylethyl terminated PI, so that polyimide/carbon fiber composites could be cured at Polymers 2024, 16, 1149 2 of 19 300 • C, and the TGA characterization of the cured material and the mechanical property test of the composites showed good heat resistance and mechanical stability [14].…”