When looking at the properties of Polyurethanes (for wheel materials), it is important to keep in mind a few things.
1.) Load capacity is the most common and often the most important. HPPT tread resists heat buildup (a leading cause of wheel failure) and can carry higher weight capacities. Softer Polyurethanes tend to have much lower capacities as opposed to harder Polyurethanes. For example, if you were moving 2000 pounds, hard polyurethane would be overkill. The opposite goes if you are moving high weights with soft polyurethane.
Although soft polyurethane is fantastic when it comes to drive wheels due to the pliability and the grip provided by the soft polyurethane, if your wheel is too hard, it will not grip the floor when driven. This deals with the coefficient of friction (COF), which is the amount of resistance an object (wheel) encounters when moving over another object (the floor). A softer wheel will have a higher coefficient of friction than a harder wheel, so this higher level of friction means a lighter load.
2.) Rebound is another property of polyurethane we keep track of. Rebound in terms of a Polyurethane Wheel refers to when a wheel flat spots, what is the ability of the wheel to roll back to its normal shape. When a wheel is subjected to a heavy load, it can cause the wheel to deform and become flat, particularly if the load is not evenly distributed across the wheels.
RELATED: Caster Wheel Polyurethane Types
As a standard, hard polyurethane has a very low rebound rate, meaning that if the cart sat loaded for an extended period of time, the wheel would flat spot and have a difficult time rolling back to shape. However, while it might flat spot, HPPT poly has a higher resistance to permanent deformation than other tread materials. The best poly to overcome this is soft polyurethane, which has higher elasticity and tends to have very high rebound rates. This gives it the ability to roll out flat spots with ease.
RELATED: How to Prevent Caster Wheel Flat Spotting on Heavy Weight Applications.
3.) Compression set is another thing we measure when it comes to the deformation of the wheel. Compression set is the Polyurethanes response to sitting for a long period of time (i.e., flat spotting). As stated above, it’s a rule of thumb that hard polyurethanes have low rebound rates, which also means that they have very high compression sets, meaning that they flat spot more commonly than other Polyurethanes. Soft Polyurethanes have high rebound, and low compression. They flat spot much less often while also being able to roll out a flat spot when it does occur.
This brings me back to “Why High-Performance Polyurethane is High Performance”
1.) HPPT is one of the highest capacity-rated Polyurethanes provided here. No matter the size of the wheel, it is classified as heavy duty according to us.
2.) HPPT polyurethane has a much higher rebound than hard polyurethanes and rolls out hard spots much better.