Synthesis and Thermal/Electrical Properties of Propynyl-Containing Difunctional Biomass-Based Epoxy Resins

With the rapid advancement of third-generation wide-bandgap semiconductor power devices, such as silicon carbide (SiC), toward higher operating temperatures and voltage ratings, traditional epoxy resin, used as encapsulation insulating materials, have struggled to meet reliability requirements under harsh operating conditions due to issues such as low glass transition temperatures ( T g ) and severe degradation of high-temperature insulation properties. In this study, a propynyl-containing difunctional honokiol epoxy resin (PDHEP) was synthesized using biomass-derived honokiol as the raw material. Through molecular structure design and curing system regulation, two curing systems, PDHEP/DDS and PDHEP/TAPT, were established by combining PDHEP with 4,4′-diaminodiphenyl sulfone (DDS) and a self-synthesized trifunctional aromatic amine curing agent containing a triazine ring (TAPT), respectively. Thermal property studies indicate that the T g and maximum thermal decomposition temperature ( T max ) of the PDHEP/TAPT system are higher than the PDHEP/DDS system, due to the higher cross-linking network density formed between TAPT and PDHEP. In terms of dielectric properties, the PDHEP/DDS system demonstrates comprehensive advantages, with an AC breakdown field strength of 113.9 kV/mm and a DC breakdown field strength of 185.2 kV/mm at room temperature. Even at a high temperature of 200 °C, these values remained at 76.3 kV/mm and 152.1 kV/mm, respectively, both significantly higher than the PDHEP/TAPT system. The PDHEP/DDS system possesses a lower dielectric constant and dielectric loss. Molecular simulation results show that the PDHEP/DDS system has a wider bandgap (3.35 eV), which explains its superior insulating properties. This study provides a solution to meet the stringent requirements for high-temperature, high-voltage packaging insulating materials in third-generation power semiconductor devices.