Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Mechanical enhancement and flame retardancy of EP modified with SED.

ABSTRACT
Epoxy resins (EP) are widely used but suffer from high flammability. Conventional flame-retardant modifications often compromise their transparency or mechanical properties, and most flame retardants are derived from petroleum-based resources. To overcome these limitations, a new molecular-designed multifunctional P/N/S-containing co-curing agent, designed SED, was synthesized from bio-based syringaldehyde, sulfaguanidine, and DOPO. Acting as a multifunctional additive, SED accelerated the curing kinetics of EP and improved its mechanical qualities and excellent flame retardancy without sacrificing the high transparency. The EP formulation containing 7 wt% SED received a V-0 rating in the UL-94 test and achieved an LOI value of 34.4%. The THR, TSP, and PHRR all significantly decreased using the EP/SED system as compared to EP; the largest reductions were 27.6%, 22.0%, and 38.1%, respectively. Investigation into its flame-retardant mechanism revealed that SED possessed excellent combined condensed-phase and gas-phase flame-retardant performance, enabling it to achieve high flame-retardant efficiency to EP at low addition levels. Furthermore, the EP/SED samples maintained high transparency and heat resistance while exhibiting significantly improved mechanical properties in tensile and flexural tests. A novel molecular design strategy is presented in this study for the development of high-performance EP suitable for applications in rail transportation and high-end optical devices.