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Polyurethane vs. UHMW

Posted by on September 2, 2020

Regarding sprocket applications in particular it seems the default request in 2020 is for “UHMW” sprockets. Indeed, UHMW is used in some sawmill sprocket applications and is widely used elsewhere in sawmills as wear parts. However, the material is not ideal for use in either a drive or idler sprocket – why is this so? Firstly, UHMW is softer than polyurethane or nylon sprocket options. While this reduces wear on the chain, the UHMW deforms easier and also has very poor dimensional stability. In fact, UHMW is notorious for thermal expansion issues which depending on the temperature swing can easily expand as much as 1/4″. UHMW sawmill sprockets also need to be machined which is much more expensive than a molded Redco 750 polyurethane sprocket.

Polyurethane on the other hand is an “elastomer”. This type of material resists deformation by returning to its original shape (at least 90% within 10 minutes of release of compression) and is more dimensionally stable than UHMW while retaining the beneficial low-wear properties it incurs on sawmill chain. They will last longer in the application reducing maintenance downtime. The drawback is that a mold must be created for the sprocket resulting in a one time tooling/setup fee for the customer (unless of course that model of sprocket already exists).

For questions on sawmill sprockets for your application please contact Redwood Plastics and Rubber.


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