Poly(methyl methacrylate) (PMMA) filled with hydroxyapatite (HA) filler has been widely used in biomaterial application. Acrylic denture base material was prepared from PMMA filled with HA. This research work attempted to investigate the effects of hydroxyapatite (HA) on the flexural properties of poly(methyl methacrylate). PMMA powder was mixed with a monomer of methyl methacrylate (MMA) stabilized with hydroquinone. Benzoyl peroxide (BPO) and ethylene glycol dimethacrylate (EGDMA) were used as initiator and crosslinking agent, respectively. The PMMA/HA composites were prepared by using heat-processing polymers powder and liquid method. The flexural modulus of PMMA was increased by the addition of HA. This is attributed to the reinforcement effects of HA. However, the flexural strength and strain was decreased in the presence of HA. Experimental data of flexural modulus for PMMA/HA composites was compared with several theoretical models and equations. It was found that the experimental data could be relatively predicted by Hirsch's model.
In this study, a montmorillonite masterbatch (OMMT-MB) containing polystyrene and organo-montmorillonite was first prepared by extrusion processes. Subsequently, blending of polystyrene (PS) and montmorillonite masterbatch (OMMT-MB) was performed by the direct melt intercalation method using a twin-screw extruder followed by compression molding. The flexural and morphological properties of PS/OMMT-MB were characterized by flexural tests and fieldemission scanning electron microscopy (FESEM). The flexural tests were carried out at two different testing speeds, i.e. 5 mm/min and 50 mm/min. The flexural modulus of PS increased significantly with the addition of OMMT. This is due to the reinforcement and stiffness of the OMMT-layered silicates. It is interesting to note that the flexural modulus of PS/OMMT-MB was higher than that of both PS and montmorillonite masterbatch (OMMT-MB). This indicates that the dispersion of OMMT in the PS was better and more homogeneous by using the montmorillonite masterbatch approach.
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