Development of PMMA–silica–alumina nanocomposites for enhanced performance

Abstract

This study focuses on alumina–silica oxide mixtures synthesised via sol–gel processing using rice husk and aluminium chloride hydroxide as precursors followed by calcination, yielding submicron particles suitable for reinforcing poly(methyl methacrylate) (PMMA). These hybrid oxide particles exhibit a well-dispersed phase composition of alumina and silica, enhancing mechanical properties when homogeneously distributed within the brittle PMMA matrix. X-ray diffraction (XRD) confirmed the crystallinity and phase structure of the particles. The PMMA composites were formulated with 1 wt.%, 3 wt.%, and 5 wt.% Al2O3/SiO2, then analysed using scanning electron microscopy (SEM), optical microscopy, and indentation testing. Vickers microhardness and tensile tests showed significant improvements in the hardness, strength, and creep resistance of the hybrid nanocomposites. The hardness increased by approximately 25.94% and creep resistance by 4.4% when 3 wt.% of Al2O3/SiO2 particles was added to PMMA, while the tensile strength increased to approximately twice that of the pure PMMA matrix. Wettability was evaluated via sessile drop measurements using water and glycerine, representing polar liquids with differing viscosities. The surface free energy and work of adhesion were calculated using the Owens–Wendt–Rabel–Kaelble (OWRK) model. The results show that even low concentrations of hydrophilic particles markedly influence the wetting behaviour, with modular surface properties emerging as a function of filler loading. Among tested compositions, the 3 wt.% oxide-reinforced composite achieved the most favourable balance of mechanical reinforcement and wettability control, identifying it as the optimal formulation for enhanced PMMA-based dental applications.