Organic–inorganic hybrid strategy toward halogen-free flame retardant, high transparent and reinforced poly(methyl methacrylate)

Copolymerization of methyl methacrylate (MMA) with flame retardant monomer is considered to be the most promising method for the preparation of transparent flame retardant poly (methyl methacrylate) (PMMA). However, the mechanical strength and heat resistance of the obtained flame retardant copolymers aren't satisfactory. In this work, the organic–inorganic hybrid PMMA copolymer is designed and synthesized by the ternary copolymerization of MMA, octavinyl silsesquioxane (V-POSS) and phosphorus-containing flame retardant monomer (DEP). V-POSS hardly affects the transparency and flame retardancy of the copolymer, but can significantly improve the thermal stability and mechanical properties. When 0.4 mol% V-POSS is copolymerized, the hybrid copolymer shows limiting oxygen index, heat release rate and visible light transmittance equivalent to the copolymer containing only DEP unit, and the initial decomposition temperature, storage modulus, flexural strength and impact strength are increased by 13°C, 21%, 11% and 23% respectively because of the cross-linking structure and the enhancement of inorganic nanoparticles. This study illustrates the reinforcing and flame retardant effects of hybrid copolymers, and provides a novel strategy for the preparation of high-performance flame retardant plexiglass.