A study of the compression molding method for manufacturing a UHMWPE liner

Abstract

Hip and knee joints are some examples of the vulnerable joints in the human body. However, due to internal or external factors, the symptoms of osteoarthritis disease may occur, so the replacement of the natural joints with an artificial ones becomes crucial. The most common material used for this part is one type of polymer, namely the ultra-high-molecular-weight polyethylene (UHMWPE) for the liner bearing, a component in an artificial hip or knee joint. Usually, the liner component of the artificial joint prosthesis is manufactured from machining process from a bar of UHMWPE material, which is made using ram extrusion process. This research aims to conduct a manufacturing process of UHMWPE liner using compression molding process, changing the powder UHMWPE into solid UHMWPE. The present method developed aimed to reduce the pressure and the amount of energy required during the compression molding process. The hardness and density tests were conducted for measuring several indicators related to the success of the solidification process. It was found that the resulting solid UHMWPE conformed to international standards for manufacturing the joints liners and polymer bearings for joint prosthesis. The best parameters resulting from the experiments were the UHMWPE hardness of 9.37 VHN and the density of 0.94 g/cm3. After a good manufacturing process resulting from this research, the ASTM international standards for joint liners and polymer bearing for joint prosthesis will easily be fulfilled in production in in Indonesia.