Preparation and properties of stretchable low temperature resistant flexible epoxy resin curing agent

Abstract

Two innovative molecular design strategies for epoxy curing agents to address the inherent brittleness and cryogenic limitations of conventional epoxy systems are introduced. A silane-modified curing agent (DETA-Si) and a flexible-chain-engineered curing agent (NBO_n) were synthesized to achieve unprecedented mechanical–electrical–thermal synergies. The DETA-Si/EP composite demonstrates a record-breaking elongation at break of 125% (22× improvement over unmodified systems) while maintaining ultralow dielectric loss (tan δ < 0.04) and thermal stability (T_d = 236 °C). The NBO_n series, incorporating rigid benzene rings and tunable aliphatic chains, exhibits exceptional cryogenic resilience: 18% elongation at 298 K with >50% ductility retention after 24-hour immersion in liquid nitrogen (77 K). Conductive composites cured with EP/NBO₁₀ show stable resistance (±5%) under 30-day cryogenic exposure. Free volume engineering, validated via WLF modeling, underpins the enhanced low-temperature performance. These advancements establish a paradigm for epoxy resins in flexible electronics operating under extreme conditions, such as flexible sensors and polar climate devices.