The present study was conducted to investigate the possibility of merging the wick-debinding and sintering of injection-molded ceramic parts into a single-step operation. In this study, the synthesized hydroxyapatite (HAp) feedstock prepared was injection moulded according to ASTM standard C1424-10 to produce green specimens. The green specimens were then debound and sintered through a single step wick-debinding and sintering process by using alumina powder as an embedment agent. The principle of this method is that it carried out at a temperature where the binder is melt, allowing it to flow out of the specimens into pores in the contacting of substrate. Once, the binder is successfully removed from the specimens, sintering process is took place to bond the particle together leading to densification of sintered specimens. From the results, it shows that the binders were successfully removed from the green specimens by capillary suction of the molten binder and single phase of HAp was presented at the sintering temperature of 1000°C.
Development of binder system based on natural resources is one the main interest among researchers in ceramic injection moulding (CIM) with the main aim of processibility of complex biomedical implant. In this paper, the influence of single binder comprised of palm stearin mixed with HAP powder was investigated. The powder and binder mixture, generally known as feedstock was analyzed for its flowability in order to get some insight for injection moulding purposes. Two different mixing temperatures were investigated for preparing the feedstock; 160°C and 70°C. The feedstocks viscosity was then evaluated using a capillary rheometer at temperature range from 70°C to 90°C. The results clearly showed that the use of 100% palm stearin was promising in providing required pseudoplastic flow for injection molding. The injection molding process can be carried out at relatively low temperature in comparison with the conventional binder systems used.
This study investigated the flow behavior of feedstock containing hydroxyapatite (HAp) powder with palm stearin (PS) based binder system. The HAp was synthesized via chemical precipitation method with the use of waste of clamshells. The result showed that single phase synthesized HAp was successfully formed at annealing temperature and pH solution of 850°C and 6.5, respectively. The synthesized HAp with a volume fraction of 65% was then mixed with PS and and Polyethylene binder at 160°C to prepare a feedstock. From the rheological test result, it was found that the feedstock exhibited a pseudoplastic behavior with low values of shear sensitivity in comparison with commercial HAp.
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