1. Field of the Invention
The present inventions relate to processes comprising crosslinking polyethylene or using crosslinked polyethylene, and to products obtained therewith.
2. Description of the Related Art
Ultrahigh molecular weight polyethylene (UHMW PE) is well known for, among other properties, its chemical resistance, low friction coefficient, high toughness, and resistance against wear. As a result, it has found numerous applications in demanding environments where some or all of the above properties are required. Equally well known is the intractability of this polymer, which is due to the fact that UHMW PE above its crystalline melting temperature, does not form a fluid phase that is of a viscosity that permits melt-processing techniques used with common thermoplastic polymers.
A negative consequence of the fact that above its crystalline melting temperature UHMW PE merely passes into a viscoelastic state, is that the original polymer particles soften but tend to substantially retain their shape. Even after relatively long sintering times at relatively high temperatures, much of the initial powder morphology may still remain. The latter, in fact, is thought to contribute to wear and ultimate failure of, for example, artificial implants made from this polymer. Attempts have been made to design processes that reduce wear. These processes are however relatively cumbersome, e.g. are ill defined, require melting the UHMW PE more than once, are time consuming, and/or substantially negatively influence other properties of the UHMWE PE such as, e.g., crack resistance.