Multifunctional flame-retardant epoxy enabled by DHAT with enhanced mechanical, UV-shielding, and dielectric performance

DHAT enabled UL-94 V-0 at only 4 wt% and raised the LOI to 29.7%. • PHRR, THR, and TSP decreased by 35.1%, 42.5%, and 30.2%, respectively. • Gas- and condensed-phase synergy suppressed volatiles and reinforced char formation. • ESP, BDE, and TD-DFT calculations clarified synthesis, pyrolysis, and UV absorption. • DHAT enhanced mechanical strength, UV shielding, and dielectric performance. A novel phosphorus/nitrogen-containing flame retardant, DHAT, was synthesized and incorporated into epoxy resin (EP). At only 4 wt% loading, EP/4DHAT achieved a UL-94 V-0 rating, and its LOI increased from 21.8% to 29.7%. The pHRR, THR, and TSP were reduced by 35.1%, 42.5%, and 30.2%, respectively. TG-FTIR, char analysis, and bond dissociation energy (BDE) calculations revealed a gas-phase and condensed-phase synergistic flame-retardant mechanism. In addition, the tensile and flexural strengths of EP/4DHAT increased by 11.4% and 77.9%, respectively. EP/4DHAT maintained approximately 87% visible-light transmittance at 600–800 nm and exhibited effective UV shielding over 200–400 nm, which was attributed to the readily accessible low-energy electronic states and strong allowed transitions introduced by DHAT. The dielectric constant and dielectric loss were also reduced. These results demonstrated that DHAT effectively integrated flame retardancy, mechanical enhancement, optical functionality, and favorable dielectric performance into EP composites. Download: Download high-res image (383KB) Download: Download full-size image