Mechanical properties enhancement of self-cured PMMA reinforced with zirconia and boron nitride nanopowders for high-performance dental materials

Abstract

We report on the mechanical properties regarding self-cured acrylic polymethyl methacrylate (PMMA) reinforced with hexagonal boron nitride (h-BN) and stabilized zirconia (8Y ZrO₂) nanopowders. The nanocomposites were prepared by using both manual and ultrasonic mixing techniques. The fabricated specimens were subjected to micro indentation, bending strength, and modulus of elasticity measurements. A fully complete polymerization process under liquid monomer was provided by ultrasonic mixing as evidenced by Fourier transform infrared (FTIR) measurement. Independently of the nanopowder used, the hardness, bending strength, and modulus of elasticity of the formed nanocomposites highly increase in values with the increase of the filler concentrations. Higher bending strengths and modulus of elasticity of the nanocomposite were recorded when using h-BN nanopowder fillers whereas hardness increases when using 8Y ZrO₂ nanopowder. Results showed that with respect to the unloaded specimens made by manual mixing, ultrasonic mixing of PMMA with a 5 wt% h-BN increased the flexural strength (FS) and the modulus of elasticity or Young's modulus (YM) values to about 550% and 240%, respectively. However, a similar concentration of 8Y ZrO₂ increased the Vickers Hardness numbers (VH) to about 400%. This may suggest that PMMA loaded with a combination of h-BN and 8Y ZrO₂ nanopowders may lead to nanocomposites with outstanding mechanical performance.

Keywords: Bending strength; Boron nitride; Hardness; Nanopowders; PMMA; Young's modulus; Zirconia.