Improvement of Microstructure and Properties of Poly(methyl methacrylate)/Hydroxyapatite Composites Treated with Zirconate Coupling Agent

Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) composite has potential application in denture base materials. Surface treatment of HA using zirconate coupling agent (ZCA) has been carried out to improve the interfacial bonding between the PMMA matrix and HA filler. The effects of different concentration of ZCA (i.e., 2-8%) on the mechanical properties of PMMA/HA composites was investigated using tensile and three-point bending flexural tests. The morphological properties of the PMMA/HA composites was characterized using field emission scanning electron microscopy (FESEM). It was found that PMMA/5HA-2% ZCA composites exhibited higher flexural strength compared to that of untreated PMMA/HA composites. This is attributed to the enhancement of interfacial interaction between PMMA and HA, which can be evidenced by the FESEM and EDX technique. The kinetics of simulated body fluid (SBF) absorption of PMMA/HA composites were studied at 37 degrees C for immersion duration of 2 months. The mathematical treatment used in analyzing the data was the Fickian diffusion and utilized Fick's second law of diffusion. It is worth mentioning that the kinetics of SBF absorption of the PMMA/HA composites conformed to Fickian law behavior, whereby the initial SBF absorption follows a linear relationship between the percentage gain at any time t and t(1/2), followed by saturation. It was found that the equilibrium SBF content of PMMA/HA composite was reduced by the ZCA treatment.