Fabrication of silicon nitride fiber–PMMA composite through free radical polymerization in batch

The strong inorganic–organic composite was successfully fabricated by combination of the super stiff silicon nitride (Si3N4) fibers and the leading flexible poly(methyl methacrylate) (PMMA) by initiating free radical polymerization in batch. Hydroxylation of Si3N4 fibers made it feasible to modify the fibers with γ-methacryloxypropyltrimethoxysilane (γ-MPS), which was identified as linkage between Si3N4 and PMMA through CC bond. The Si3N4–PMMA composite had a reduced modulus of 4.72 GPa, with the improvement of at least 52% to the matrix. The observation on morphology and structure of the composite demonstrated that the inorganic fibers were uniformly dispersed in the polymer matrix, and most importantly, they were well cross-linked by chemical bonds and van der Waals. The thermal stability of Si3N4–PMMA was raised with an increase in thermal decomposition and glass transition temperature. The composite with super mechanical properties and thermal stability may have potential applications in aerospace industry and civil engineering fields.