A Flame‐Retardant Epoxy Resin Containing P/N/S With Comparable Transparency and Mechanical Performance

ABSTRACT A flame retardant (MBATP) with exceptional performance, incorporating three flame‐retardant elements (P/N/S), was synthesized using 2‐amino‐1,3,4‐thiadiazole, 9,10‐dihydro‐9‐oxo‐10‐phosphophenanthrene‐10‐oxide, and 4‐methylsulphonyl benzaldehyde as raw materials, along with a curing agent to produce flame‐retardant epoxy resins (FREPs). The chemical structure of MBATP was confirmed through FT‐IR, 1 H NMR, and 31 P NMR characterization. The study investigated the effects of different contents of MBATP on the curing behavior, flame‐retardant effect, thermal stability, combustion characteristics, mechanical properties, and transparency of FREPs. The study revealed that the introduction of MBATP led to a decrease in the maximum decomposition rate while simultaneously facilitating the early decomposition of epoxy resin (EP). The FREP‐4 (4 wt% MBATP) attained a V‐0 rating through the UL‐94 standard, accompanied by an oxygen index of 33.5%. Furthermore, total smoke, the peak heat release rate, and total heat release emission of FREP‐4 were diminished by 26.1%, 67.4%, and 25.5%, respectively, compared with EP. Residual carbon and volatile gas emissions tests showed that MBATP effectively contributed to flame retardancy in both the condensed phase and gas phase. The FREPs exhibit a significant degree of transparency, and their mechanical properties have been slightly enhanced. This study has promising applications in advanced optical technologies.