Investigation of the Insulation Characteristics of TPU/EP Composites Under Cold Thermal Shock

To improve the issue of the decreased toughness and electrical performance of epoxy resin (EP) in thermal shock environments, we prepared thermoplastic polyurethane elastomer (TPU)-filled modified EP composites. We also studied the mechanical and electrical performance of these composites, which had different TPU filling contents, under thermal shock conditions. The results indicated that after 240 h of thermal cycling between -15 °C and 100 °C, the TPU/epoxy composites, when compared to unmodified EP, exhibited a 10.1% enhancement in their elastic modulus, a 15.3% increase in their elongation at break, a 22.3% improvement in their tensile strength, and a 47.8% increase in their impact strength. Moreover, their volume resistivity increased by 10.5% and their AC breakdown strength improved by 52.1%. In contrast, their dielectric constant and dielectric loss experienced reductions of 40.2% and 7.5%, respectively. This study demonstrates that introducing flexible TPU molecular chains into the resin significantly enhances the toughness of EP structures. Additionally, the new cross-linked structures formed within the TPU/EP composites improve their insulation performance under thermal shock conditions.