Changes in polyurethane formulations change much more than the hardness. This is why it’s important to let the manufacturer know what your application is so we can give you the best formulation for your product.
Here’s an example: these two balls are the same hardness however their chemical formulations are quite different. Observe:
This demonstration illustrates the tremendous versatility of cast urethane. The ball on the left is a Dead Formula and the ball on the right is a Super Ball Formula. So what is it that makes such a dramatic difference?
Let me give you a brief overview of how cast polyurethane is made.
Urethane at its simplest is a polyol connected to an isocyanate and cross-linked with a curative.
The most common polyols are polyester or polyether, and there are many different types of each.
Polyesters offer more:
- Abrasion resistance
- Tear Resistance
- Solvent and oil resistance
Polyethers offer more:
- Low temperature flexibility
- Perform better in high-speed or dynamic applications
The polyol is combined with an isocyanate to create a pre-polymer. The most common isocyanates are TDI and MDI, however, there are several others that are used in specialty applications. TDI delivers good properties at high temperatures while MDI delivers good properties at low temperatures.
The pre-polymers are cross-linked with a curative. There are dozens of chemicals used as curatives for polyurethanes and each imparts different physical properties to the finished product. It is also possible to blend curatives, thus giving us an infinite variety of formulations. Physical properties are also affected by the ratio of curative to pre-polymer, which is called stoichiometry.
There are also additives that can affect properties such as coefficient of friction, tear resistance and electrical conductivity.
PSI Urethanes processes seven different pre-polymers and numerous different curatives every day. Because we hand weigh and mix every pour, we are able to adjust the formula to meet your requirements. Processors using meter/mix machines cannot easily change formulations from product to product.
So remember to tell the friendly salesperson at PSI how your product will be used. That will allow the experts at PSI to formulate the best urethane for your product.