Intrinsic flame‐retardant epoxy resin composites with benzoxazine: Effect of a catalyst and a low curing temperature

Abstract

ABSTRACT Three kinds of inherent flame‐retardant epoxy resin (EP) composites with 20 wt % benzoxazine (BOZ) were prepared with different curing processes with 2‐methyl‐1H‐imidazole (MI) as a catalyst or/and changes in the curing temperature. The effects of the curing process on the flame retardancy, thermal stability, mechanical properties, and curing behaviors were investigated. The composite with added MI cured at low temperature (EBM–LT) had the best properties. It possessed a 35.3% limiting oxygen index and achieved a UL 94 V‐0 rating. Thermogravimetric analysis indicated that EBM–LT had the best thermal stability among the three kinds of EP composites with BOZ. The EP composites with BOZ mainly displayed a condensed‐phase flame‐retardant mechanism. The mechanical properties improvement was attributed to the formation of a heterogeneous network. Differential scanning calorimetry indicated that MI reacted with EP and catalyzed the homopolymerization of BOZ, and EP reacted with BOZ. Fourier transform infrared spectroscopy analysis indicated that curing at lower temperature caused the formation of more homopolymers of BOZ. The relationship of the curing process, network structure, and properties of EP composites with BOZ was established; this could help with the design of high‐performance EP composites with BOZ. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47847.