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The poly(methyl methacrylate)/hydroxyapatite (PMMA/5HA) composites were prepared by using heat-processing polymers powder and liquid method with a ratio of 10 : 4 according to the dental laboratory practice. The hydroxyapatite (HA) was surface treated using 3-(trimethoxysilyl) propyl methacrylate (c-MPS) with different concentrations based on HA (i.e., 2, 4, 6, and 8%). The chemical treatment of HA was examined using Fourier Transform Infrared Ray Spectroscopy (FTIR). The mechanical properties of PMMA/5HA composites were characterized using tensile, 3-point bending flexural and fracture toughness tests. The morphological properties of the PMMA/5HA composites were characterized using field emission scanning electron microscopy (FESEM). The intensities of absorption bands at 840, 873, and 1031 cm À1 which are corresponding to SiAO stretching were observed and became higher as the increasing concentration of c-MPS for the HA treatment. This indicates that the HA was successfully treated by c-MPS. It is interesting to note that the flexural modulus and strength of PMMA/5HA was increased significantly by 6% c-MPS. The improvement of the mechanical strength could be related to the enhancement of interfacial interaction between PMMA and HA by the surface treatment of c-MPS. In addition, the fracture toughness properties of PMMA/5HA composites were also influenced by the different concentration of c-MPS. It is believed that the c-MPS could act as a good silane coupling agent for the PMMA/5HA composites.

A series of maleic anhydride grafted poly(lactic acid) (PLA-g-MAH) was prepared by mixing PLA, dicumyl peroxide (DCP) and maleic anhydride (MAH). Effects of DCP and MAH concentration on the grafting percentage were determined. PLA composites were prepared via melt mixing with halloysite clay (HNC; 3 wt%) and various amount of PLA-g-MAH (4-10 phr) using internal mixer followed by compression molding. Properties of the PLA composites were characterized using three-point bending flexural tests, scanning electron microscopy and differential scanning calorimetry. It was found that the grafting percentage of PLA-g-MAH was influenced by both DCP and MAH concentrations; however, DCP showed more profound effect. By the addition of PLA-g-MAH, the adhesion between PLA and HNC improved, which can be manifested by the enhancement in flexural properties. Degree of crystallinity of PLA/HNC increased significantly by the addition of PLA-g-MAH.

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Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) denture base composites were prepared using heat-processing polymers powder–liquid method, according to dental laboratory practice. The HA was pre-treated by isopropyl triisostearoyl titanate coupling agent (TCA) in order to improve the interfacial bonding between HA and PMMA. The effects of different concentration of titanate coupling agent (i.e., 2–8%) on the mechanical and morphological properties of PMMA were investigated. It was found that PMMA/2% TCA-treated HA composites exhibited higher flexural modulus and strength compared to PMMA/untreated HA composites. This is attributed to the enhanced interfacial interaction between PMMA and HA by the titanate coupling agent. However, for the PMMA/HA treated with 6% and 8% of TCA, the flexural properties was slightly reduced, which may associated to the plasticizing effects caused by excessive concentration of coupling agent. In addition, the fracture toughness properties of PMMA/5HA composites were influenced by the different concentration of TCA. The thermal properties of the PMMA/HA composites were enhanced by the treatment of titanate coupling agent.