Papers by Author: Kitiya Wasoontararat

Abstract: In this study, a combination of powder printing technique and two-stepped heat treatment was utilized as a mean to prepare porous high density polyethylene structure. Physical and mechanical properties of the resulting structure were then characterized by porosity measurement and monotonic tensile test. It was found that the relationship between structure and properties was strongly influenced by processing conditions including compositions, treatment times and treatment temperatures. This process could increase the properties of porous high density polyethylene significantly over the single-stepped heat treatment without destroying porous structure. Porous high density polyethylene bodies having a porosity ranging from 46-58 percents with tensile strength up to approximately 4 MPa could be successfully prepared in this study.

Abstract: Influence of using different layer thickness in three dimensional printing process of calcium sulfate based sample prior to phosphorization process was studied. Phase composition and mechanical properties of the resulting structure were characterized by x-ray diffraction and three-point bending techniques. It was seen that transformation rate, phase composition and flexural strength were all affected by the change in layer thickness. Too high layer thickness, 0.2 mm, caused the disintegration of sample during phosphorization while too low layer thickness, 0.08 mm, decreased the transformation rate. The optimised layer thickness in this study which gave both high conversion rate and flexural properties was found to be 0.1 mm.

Abstract: In this study, in vitro acellular bioactivity and tensile bonding strength of hydroxyapatite (HA) coating synthesized by sol-gel technique after long-term storage in simulated body fluid (SBF) for up to 32 days were studied. After soaking in SBF, it was observed that new bone-like apatite layer was formed on the coating indicating the bioactive nature. Bonding strength of sol-gel coated rods was found to decrease with soaking times, from 55 to 30 MPa. In comparison to adhesive bonded titanium rods which were used as control specimens, the values were found to be equal or even greater in certain soaking periods. Debonding at adhesive-titanium interface was the failure mode indicating that the coating is still intact. Therefore, it could be concluded that this sol-gel coating is bioactive and the coating adhesion to substrate is sufficiently strong.