Polymer UHMWPE ultra-high-molecular-weight

When polytetrafluoroethylene (PTFE) was Introduced in the early 1960 s the life of total replacement hip joints was limited to about three years by the poor wear characteristics of the polymer. When ultra-high molecular weight polyethylene (UHMWPE) replaced PTFE, the rate of penetration of the metallic component into the polymeric component was reduced to such an extent that loosening emerged as a major aspect of prosthetic life. There is, nevertheless, a need to pursue studies of the wear of prosthetic materials to facilitate the development of satisfactory materials which can be used with confidence in long-life prostheses. 

Enhancing the wear resistance of polymers (e.g., ultra-high-molecular-weight polyethylene-UHMWPE-used for in vivo implants, such as artificial hip joints). ... 

Valenza, A. Visco, A.M. Torrisi, L. Campo, N. Characterization of ultra-high-molecular-weight polyethylene (UHMWPE) modified by ion implantation. Polymer 2004, 45, 1707-1715. 

Two sets of experiments were performed. In the first set, three polymers with very different mechanical properties were chosen to determine their response to this experiment. Polycarbonate PC, rigid polyvinyl chloride PVC, and ultra-high molecular weight polyethylene UHMWPE, were loaded with 10, 8.5, and 7.2 N and tested at 0.04 m/s sliding speed. In these tests, the friction force was continuously... 

The blood bag case study illustrates the use of polymeric film as a flexible container. It considers the permeability of polymers, plus processes for fabricating plastics film. Plasticised PVC has dominated the market for years, but there could be a changeover to flexible polyolefin films. The case study on replacement joints for implanting in the body illustrates wear and the effects of wear debris. Research continues on improving the wear resistance of the ultra high molecular weight polyethylene (UHMWPE) and mitigating the effects of sterilisation on the implant properties. 

The focus in this chapter will be on the two main polyolefin polymers, namely polyethylene (PE) and polypropylene (PP). The latter especially has established itself as a very versatile fiber with unique applications in the textile and nonwoven industry. Polyethylene, on the other hand, has not been widely used as a fiber compared to other synthetic polymers such as PET, PP, and nylon, due in part to its low melting point. This chapter will, however, discuss ultra-high molecular weight polyethylene (UHMWPE) fiber that given its success and uniqueness in the synthetic fiber industry. 

The ultra-high molecular weight polyethylene used in orthopedic applications is a type of polymer generally classified as a linear homopolymer. Our first task is to explain what is meant by all of these terms. Before proceeding to a definition of UHMWPE, one needs to first understand what constitutes a linear homopolymer. 

On the other hand, some polymers show an initial increase in crystallinity, demonstrated by an increase in density. At relatively low doses (< 200 kGy), ultra high molecular weight polyethylene (UHMWPE) appears to show an increase in crystallinity. Since UHMWPE has a... 

Poly Hi Solidur Plastics India Limited [4] developed products for use on the Indian Railways based on ultra-high molecular weight PE (UHMWPE Hoechst s Hostalen GUR). The base polymer is mixed with patented additives and uses a computer controlled sintering process and sophisticated fabrication methods to produce a material which is claimed to have much higher values for a number of technically important properties such as wear, chemical and water resistance, impact strength and dynamic coefficient of friction. The growth of the market for UHMWPE products is briefly discussed, and the applications targeted by Poly Hi Solidur Plastics are discussed. 

Liu and co-workers [16] investigated the wear behaviour of ultra-high molecular weight polyethylene (UHMWPE) polymer. They concluded that the applied load is the main parameter and the wear resistance improvement of filler reinforced UHMWPE was attributed to the combination of hard particles, which prevent the formation of deep, wide and continuous furrows. Bijwe and co-workers [17] and Xu and Mellor [18] tested polyamide 6 (PA), polytetrafluoroethylene (PTFE) and their various composites in abrasive wear under dry and multi-pass conditions against SiC paper on a pin-on-disc tribometer. They concluded that the polymers without fillers had better abrasive wear resistance than their composites. 

For SSE, monolithic or powder billets are used. In the latter case, the polymer powder is compacted, heated to the temperature close to the melting temperature and then extruded. The extrudates of ultra high molecular weight polyethylene (UHMWPE) (8), polymerization-filled polyethylene composites (7,9)... 

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