An intrinsic flame‐retardant and heat‐resistant vinyl ester resin by crosslinking with diisocyanate, styrene and phosphorus‐containing hydroxyl compound

Abstract In this work, 2‐(6‐oxido‐6H‐dibenz<1,2>oxaphosphorin‐6‐yl)‐methanol (ODOPM) was synthesized, and covalently introduced into vinyl ester resin (VER) by combining with 4,4′‐diphenylmethane diisocyanate (MDI). The influences of ODOPM and MDI on the thermal properties, flame retardancy, and flame‐retardant mode‐of‐action of the resin were investigated. When the phosphorus addition reaches 1.3 wt%, the limiting oxygen index (LOI) of VER/ODOPM‐1.3 boosts to 30.3% and vertical burning (UL‐94) rating increases to V‐0. Compared with the virgin VER, the peak heat release rate (PHRR) and total heat release (THR) of VER/ODOPM‐1.3 are significantly reduced by 64.2% and 35.1%, respectively. The introduction of ODOPM and MDI significantly enhances the flame retardancy of VER. ODOPM and MDI are chemically linked to the polymer network of VER, which increases the glass transition temperature (Tg) and rigidity. This work offers a facile method for improving both thermal and flame‐retardant properties of vinyl ester resin.