UHMWPE (Ultra High Molecular Weight Polyethylene) is a thermoplastic polyethylene with very long molecular chains which transfers load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. It has very high abrasion resistance, shows zero water absorption, is self-lubricating and has a friction coefficient only slightly above most filled PTFEs. As a rigid material, it needs an energizer to work effectively as a sealing material.
Why use UHMWPE?
The abrasion wear resistance of UHMWPE is between 5 and 10 times greater than that of filled PTFE materials and it is stable in all hydraulic fluids, with high resistance to acids, bases and aggressive media. The water repellent, zero swell and self-lubricating properties make it ideal for use in aqueous solution applications where long service life can be achieved. It has very high extrusion resistance and the material is also particularly resistant to ionizing radiation in comparison to other sealing materials.
UHMWPE seals are ideally suited to water sealing applications and the material toughness provides excellent wear resistance in applications where the media being sealed is abrasive or the system is subject to contamination and dirt ingress. It is also physiologically safe making it very suitable for use in the food, beverage and pharmaceutical processing industries. UHMWPE has limited resistance to aromatic and halogenated hydrocarbons and a usage limiting factor for this material is the high temperature capability; recommended operating range is -200oC (-328oF) up to just +80oC (176oF). With care, under low pressure and speed applications for example, operation at up to +120oC (248oF) can be successful and for brief periods, such as during sterilization processes, higher temperatures can be tolerated.