Toughening Low‐Temperature Curing Alicyclic Epoxy Resin via Epoxy Compound Containing Flexible Side Chains

Although low‐temperature (≤ 100°C) curing of alicyclic epoxy resin (CEP) avoids the cracking issues associated with high‐temperature (120°C–180°C) curing, the resulting material still suffers from insufficient toughness. To address this limitation, it is typically necessary to introduce a second‐phase modifier or incorporate flexible segments into the resin structure. However, conventional second‐phase modifiers tend to compromise other desirable properties—such as heat resistance—or suffer from poor dispersion within the epoxy matrix. Herein, an aliphatic side‐chain epoxy resin (BD‐S‐182) and an aliphatic side‐chain epoxy bisphenol A (DGEBDDBA) are synthesized to improve the mechanical properties and thermal resistance of the material at the molecular level through cross‐linking. Both BD‐S‐182 and DGEBDDBA can enhance the impact strength and elongation at break of cycloaliphatic epoxy resin (2021P) without altering the original low‐temperature curing mechanism. The best impact resistance strength of BD‐S‐182 and DGEBDDBA is 45.1 and 52.4 kJ/m 2 , increasing by 226.8% and 279.7%, and the elongation at break can reach 43.71% and 51.36%, increased by 168.8% and 215.9%, respectively, compared with low‐temperature curing virgin resin. The thermal decomposition temperature ( T d5% ) of DGEBDDBA with 10 wt% is increased from 226.3°C to 275.1°C, and that of BD‐S‐182 with 30 wt% is increased to 241.7°C.