Team Discussion
The field of mechanical engineering often involves working with various polymers, each with its own set of advantages and challenges. Ultra-high molecular weight polyethylene (UHMWPE), in particular, has proven to be exceptionally valuable in demanding environments.
Products used in pilot plants and chemistry labs are often subject to harsh treatments: acids, solvents, pressures and high temperatures. To withstand these conditions, products were made from chemically resistant polymers like polytetrafluoroethylene (PTFE) or polyether ether ketone (PEEK).
However, these polymers come with their own set of challenges, including high costs and complexities associated with molding due to their high melting points. Sometimes, a cheap component that can be easily injection molded, has a low coefficient of friction and won’t melt when cleaned with a solvent is needed.
Polyethylene (PE) meets most of these criteria. It is resistant to the harshest chemicals, such as hydrofluoric acid (famously used in the TV show Breaking Bad). If someone were coated in hydrofluoric acid while holding a tub of butter, they would melt away, but the PE butter tub would remain intact.
Surprisingly, while PE can resist acid, it is not very effective when used with acetone, a solvent commonly used as a cleaning agent in chemistry labs. This led to the discovery of ultra-high molecular weight polyethylene (UHMWPE – pronounced ‘oohmpee’), also known as PE1000.
What’s so great about UHMWPE?
• It has an amazing strength to weight ratio
• It has the highest impact strength of any thermoplastic presently made
• It has a very low coefficient of friction (when running on stainless steel, for example)
• It is highly resistant to abrasion
• It is self-lubricating
• It is relatively cheap
• It resists most chemicals (including acids, alkalis and other organic solvents)
• It has a relatively low melting point
So, what is UHMWPE used for?
It can be used in simple components such as bearings, but it’s also been used in protective clothing since WWII. However, a primary market for this material is in medical implants. Due to some of the benefits mentioned above, UHMWPE is being used increasingly for orthopaedic and cardiovascular implants.
Dr Rhona Sinclair, senior engineering consultant at Team Consulting adds:
If you’re planning to use UHMWPE, be warned!
The material is notoriously tricky to machine, and problems can occur when injection molders don’t consider its shrinkage properly. If you’re going to use it, make sure your manufacturer has previous experience with it.
Complexities aside, the performance of the material still makes it a fantastic choice for many applications. Its characteristics, coupled with its reliability and performance, make UHMWPE a popular polymer.
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