Synthesis and Effects of Copolymers Polymerized via RAFT Polymerization on the Mechanical Properties of Epoxy Resin Composites

Abstract

Epoxy resins are used in various industries because of their excellent physical and chemical properties. However, they exhibit low toughness, which is attributed to the high crosslinking density of the epoxy matrix. Controlling the crosslinking reaction is challenging. In this study, functional copolymers are used as additives to overcome these limitations. We combine 2-hydroxyethyl methacrylate, methyl methacrylate, and glycidyl methacrylate with polycaprolactone macro-CTA via RAFT polymerization. Four types of functional copolymers are polymerized by varying the molecular weight of the main chain and the ratio of the synthesized functional monomers, and successful polymerization was confirmed by 1H-nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The tensile, flexural, and impact strengths are measured to evaluate the effect of these functional copolymers on performance enhancement. As a result, the mechanical properties are improved, and the reductions in Tg and modulus are minimized. Furthermore, FE-SEM image analysis of the cured epoxy resin fracture surface reveals a smooth transition to a rough surface, verifying the enhanced mechanical properties of the epoxy resin.