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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.

Poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) composites have potential applications in bone cement, prosthesis, and dental implant. In this study, PMMA containing 5 wt% of HA is prepared using polymerization followed by compression molding. PMMA and HA powder are ground using planetary ball milling. The grinding time takes from 30 to 120 min. The effects of the grinding time and particle size of the PMMA/HA powder on the flexural properties and morphology of the composites are investigated. The structure patterns of PMMA/5HA are characterized using X-Ray diffraction (XRD). No new phase is observed in the XRD pattern with the different sizes of PMMA/HA powder. This indicates that planetary milling solely reduces the size of PMMA/ HA powder. However, it does not modify the structure of PMMA and HA. A reduction of ~40% in the particle diameter is observed in both PMMA and PMMA/5HA powder after subjected to planetary milling for 60 min. For the planetary ball mill-ground PMMA/HA powder, the flexural modulus of the respective PMMA composites is slightly increased. Planetary milling can increase the volume of fine particles in the composites specimens, which results in a more homogeneous distribution of HA and a reduction of void contents in PMMA matrix. The reduction in void content is observed on the fractured surface of PMMA composites through field emission scanning electron microscopy.

Poly(lactic acid)/halloysite nanotube (PLA/HNT) nanocomposites were prepared using melt compounding followed by compression molding. Epoxidized natural rubber (ENR) was used to toughen the PLA nanocomposites. The properties of PLA/HNT nanocomposites were characterized by impact tests, thermal analysis (DSC), morphological analysis (FESEM, TEM), and Fourier transform infrared spectroscopy (FTIR). Water absorption tests were performed at three immersion temperature (30, 40, 508C). The maximum water absorption (M m ), diffusion coefficient (D), and the activation energy of water diffusion (E a ) were determined. The impact strength of PLA/HNT6 nanocomposites was increased significantly to 296% by the addition of 15 wt % ENR. The incorporation of HNT and ENR increase its nucleation effect and assist in the crystallization process of PLA. The HNT has good affinity with PLA and ENR, which was revealed by TEM and FTIR. The M m of PLA was increased in the presence of HNT and ENR. Nevertheless, the D value and the E a of the PLA nanocomposites were found to be affected by the HNT and ENR contents.

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