Ultra high molecular weight polyethylene compression molding

At a conceptual level, polyethylene consists only of carbon and hydrogen, as was described in the previous chapter. However, if the discussion of polyethylene is to proceed from ideal abstractions to actual physical implants, three "real world" steps need to occur. First, the ultra-high molecular weight polyethylene (UHMWPE) must be polymerized from ethylene gas. Second, the polymerized UHMWPE, in the form of resin powder, needs to be consolidated into a sheet, rod, or near-net shaped implant (Figure 2.1). Finally, in most instances, tire UHMWPE implant needs to be machined into its final shape (Figure 2.1). A small subset of implants are consolidated into their final form directly, in a process known as direct compression molding (DCM), witiiout need of additional machining. 

The ballistic properties of high performance fibers such as ultra high molecular weight polyethylene (UHMWPE) and aramid and their composites are very well known. The ballistic properties of flax, hemp, and jute fabric reinforced PP composites processed by hot compression molding have also been investigated. It has been shown that flax composites exhibited better properties when compared with hemp and jute composites [48]. 

Gsell RA, Taylor GK, Lin ST. Shelf aging of net shape compression molded 1900H ultra-high molecular weight polyethylene (UHMWPE) components. Transactions of the 44st Orthopedic Research Society, New Orleans, LA 1998 February 13-16, p. 364. 

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