Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE A novel class of transparent flexible epoxy films are developed via fast-curing process using M-XDA as the curing agent, achieved by strategically modulating the molecular ratio of hydrogenated bisphenol A epoxy resin (HBPA) and ethylene glycol diglycidyl ether (EGDE) to optimize optical transparency, flexibility, electrical insulation, and barrier performance.

ABSTRACT
Transparent and flexural epoxy resin represents an emerging class of materials for advanced encapsulation and adhesives in the electronics and semiconductor industries. Although toughening components have been reported to improve EP flexibility, multi-stage curing processes for complete crosslinking require optimization, and EP films' comprehensive properties (flexibility, optical transparency, water barrier, and electrical insulation) have rarely been systematically co-evaluated. To address these challenges, a novel class of transparent and flexible epoxy films was developed through a fast curing process (80°C/20 min) using m-xylylenediamine (M-XDA) as the curing agent. By strategically modulating the molecular ratio of hydrogenated bisphenol A epoxy resin (HBPA) and ethylene glycol diglycidyl ether (EGDE), the optimal balance of multifunctional properties, including exceptional optical transparency, mechanical flexibility, electrical insulation, and barrier performance was achieved. Among the synthesized variants, H3:E7 epoxy demonstrates outstanding characteristics: excellent transparency (transmittance of 90.6%), remarkable flexibility (> 100,000 bending cycles), low water vapor transmission rate (4.1 g·m−2·24 h−1), superior insulation (1.4 × 1014 Ω·cm) and high adhesive strength (13.4 MPa). Isothermal curing kinetics analysis confirms the scientific validity of the optimized 80°C/20 min rapid-curing protocol. This work establishes a facile yet effective methodology to expand the application scope of epoxy resins in high-value technological domains.