The pyrolysis behavior of typical epoxy/amine system: From degradation product to the mechanism ofchemical bond breakage

Abstract

With the ever-growing demand and large-scale production, carbon fiber reinforced polymer composites have become an integral part of human life, yet face the challenging issue of being difficult to degrade and recycle. Pyrolysis technology allows the reclamation of the fibers by thermal decomposition of polymer matrix. However, due to the complex chemical reaction during pyrolysis, the degradation mechanism is still no unified consensus. In this paper, the molecular simulation was implemented to analyze the pyrolysis process of three typical epoxy matrix in order to thoroughly analyze the pyrolysis characteristics and degradation behavior. The results showed that in the epoxy crosslinked networks, chemical bond breaking positions were concentrated in the vicinity of oxygen and nitrogen atoms. The reason was found that the oxygen atoms was susceptible to electrophilic reagent through the analysis of the electronic structure, which caused the chemical bond around the oxygen atom to break first during the pyrolysis. Based on the simulation results, terephthalic acid chloride was selected as epoxy matrix catalyst and had great catalytic degradation effect which was proved by experiments. The relationship between the structure of the matrix and the degree of degradation was further confirmed by comparing the activation energy. Through this study, the degradation mechanism of epoxy matrix was discussed in detail, and the essence and principal of the typical bond breakage were also revealed. Based on these studies, a new method for designing and screening efficient epoxy matrix pyrolysis catalysts can be proposed.