Synthesis and characterization of polybenzoxazine/silica‐based hybrid nanostructures for flame retardancy applications

The objective of this study is to develop polybenzoxazine-silica nanocomposite systems endowed with greater thermal and fire performance. For this purpose, the 3-aminopropyltrimethoxysilane and bisphenol A-based benzoxazine (BA-3aptms) was synthesized. Also, smooth and spherical silica nanoparticles of 50 nm size were prepared following the Stöber's method. The influence of the nanoparticle size and geometry on the properties (laminar morphology, thermal, dynamic-mechanical, hydrophobicity, and flame retardancy) of the polybenzoxazine/polysilsesquioxane material was investigated. Also, nanocomposites from the conventional benzoxazine (BA-a) and SiO2 nanoparticles were synthesized for comparative purposes. The addition of nanoparticles in both polybenzoxazines improved the mechanical, thermal and flammability properties. Likewise, the presence of these nanoparticles conferred to the material a more hydrophobic surface (contact angle around 95°). Particularly, the Pr(BA-3aptms)/NP nanocomposites presented better properties than the BA-a-based systems, due to the presence of laminar-oriented polysilsesquioxane networks chemically bonded to the silica nanoparticles at nanoscale.