Preparation of high transparency, thermal stability, flame retardant polymethyl methacrylate nanocomposite via gamma-radiation polymerization

Abstract

Achieving flame retardancy and thermal stability in poly(methyl methacrylate) (PMMA) while maintaining its inherent high transparency presents a significant challenge. In this work, we successfully fabricated an exceptional composite (P-SiO2-PMMA) with high transparency, flame retardancy, and thermal stability using 60Co γ-ray irradiation-induced copolymerization of methyl methacrylate (MMA), 2-hydroxyethyl 2-methyl-2-propenoate phosphate (HEMAP), and nano-silica (SiO2). The impact of the HEMAP on the crystal, optical, thermal stability, and combustion behavior properties of P-SiO2-PMMA has been investigated. P-SiO2/PMMA forms a three-dimensional network cross-linked molecular chain structure, enhancing the thermal decomposition temperature (Tdi), maximum thermal decomposition temperature (Tmax), glass transition temperature (Tg), and reducing the coefficient of thermal expansion (CTE). HEMAP and SiO2 significantly enhance the flame retardancy of the material. The limiting oxygen index (LOI) value of transparent flame-retardant 20-P-SiO2/PMMA composite material increased from 17.5% for PMMA to 23.2%, with a 47.3% decrease in peak heat release rate (PHRR). The flame retardant mechanism was also investigated. This study offers a novel approach for the industrial application of high transparency, thermal stability, and halogen-free flame-retardant PMMA composite.