High-efficiency manufacturing of epoxy resins through two-point initiation of frontal polymerization

Two-point initiation of frontal polymerizations (FPs) is a highly promising approach to enhance the curing efficiency of epoxy resins. However, the mechanical properties may be compromised due to the void accumulation at the merging interface. In this study, we proposed a two-point FP strategy for the rapid and energy-efficient manufacturing of epoxy resins without compromising their mechanical properties. First, density function theory (DFT) calculations were performed to elucidate the microscopic mechanism of FP. The voids and chemical composition of the merger by two-point FPs were characterized by X-ray micro-computed tomography and thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy, aiming to comprehend the frontal characteristics and mechanical properties of the cured epoxy resins. The results revealed that high temperature generated during FP led to intense resin pyrolysis, resulting in significant gas formation (e.g. CO2) at high initiator concentration. These gas products became trapped at the merger as columnar-like voids, thereby compromising the mechanical properties of cured epoxy resins. Finally, we established a processing window for efficient fabrication of high-performance epoxy resins by simultaneously tailoring the number of initiation points, initiator concentration and initial resin temperature. The results demonstrated this strategy could significantly reduce curing time and enhanced energy efficiency without sacrificing mechanical performance of epoxy resins compared to conventional techniques.