Building Block Orchestration Enables Efficient and Uniform Curing for Tough and Highly Insulating Epoxy

As pivotal dielectric materials for high-voltage insulation, epoxy resins inherently suffer from curing-induced heterogeneities via self-accelerated exothermic reactions, generating nonuniform cross-linking networks and residual stresses that escalate failure risks under multiphysical stresses. This work pioneers a building block orchestration strategy employing coordinated long-/short-chain epoxy hybrids to fundamentally resolve the exotherm-kinetics dichotomy. By leveraging the low reactive group concentration of long-chain monomers coupled with the enhanced molecular mobility of short-chain components, this approach successfully resolves the traditional trade-off between curing exotherm and reaction kinetics, achieving both efficient and homogeneous curing as well as an optimized cross-link network. This synergy delivers enhanced toughness (achieving 25% higher impact strength in HMN than SMN) without sacrificing strength or thermal stability while maintaining excellent electrical insulation (breakdown strength reaching 72 kV/mm), minimizing space charge accumulation, and reducing electric field distortion. These advancements hold promise for improving the long-term reliability of materials under high-field conditions. Ultimately, this work presents an innovative design framework for large-scale castable epoxy materials tailored for high-voltage insulation in power applications.