Acid-induced Degradation Method for Bisphenol A-based Cured Epoxy Resin

Abstract

Cured epoxy resin is widely used in versatile applications, including electronic materials and adhesives, owing to its excellent thermal stability and mechanical properties. Due to its highly cross-linked network structure, however, the establishment of its recycling process remains a significant challenge. In this study, we investigated the acid-induced degradation behavior of cured epoxy resin to explore its potential as a new chemical recycling method for thermosetting resins. As a typical example, when a dichloromethane dispersion of small pieces of cured epoxy resin containing bisphenol A as a building block was treated with trifluoromethanesulfonic acid (5 equiv) at ambient temperature for 1 d, the heterogeneous system gradually turned homogeneous, yielding soluble products. Furthermore, a model reaction using a low-molecular-weight compound, N,N-bis(2-hydroxy-3-phenoxypropyl)aniline, which was obtained from glycidyl phenyl ether and aniline, under the same conditions indicated that no cleavage of C－N and C－O bonds occurred. It suggested that the chemical bond between the isopropylidene group and the aromatic rings within the bisphenol A unit was supposed to be cleaved selectively under the examined conditions.