Hobbyists are often unsure of the differences between closely related plastics. When it comes to two commonly available plastics in the polyethylene family: “High Density Polyethylene” (HDPE) or “Ultra-High Molecular Weight Polyethylene” (UHMWPE or simply UHMW) – what is the difference? Are there any times it’s critical to use one verses the other?
The answer is in many cases the differences are not pronounced but there are a couple things to watch out for.
Where the products are more or less equivalent is any application where they’re being used as, for example, a spacer, a lining, a surface, or other “static” applications. Both products will appear to be the same color and will be the same weight. It’s when mechanical properties start getting involved that you should be concerned. Firstly, UHMW takes significantly more impact than HDPE does, so if you have an application where a part is being banged around – UHMW should be your choice. UHMW is also significantly slicker and an application involving “sliding” UHMW is the ideal choice. An example would be as sled rails on a snowmobile or toboggan: UHMW will traverse the snow much better! You can in fact find some good Youtube videos that make a comparison between the two materials on this application.
One note about the static applications listed above is that HDPE is superior as a cutting board. While both products are food grade and work great in the application, UHMW will dull blades over time whereas HDPE will not. With both products being highly available, HDPE would be the better choice. This is why HDPE is preferred for synthetic ice as well.
Speaking of other properties the plastics are pretty comparable with their UV resistance (poor), chemical resistance, availability, machinability, and heat tolerance. As always, if you’re unclear what to use for your application just contact Redwood Plastics and Rubber for assistance.
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