Your browser is out of date.
You are currently using Internet Explorer 7/8/9, which is not supported by our site. For the best experience, please use one of the latest browsers.
Urethane can be custom formulated to achieve specific physical properties. However, with a wide variety of physical properties available for custom urethane parts and products, customers often have questions regarding the specifications and materials needed for their specific application.
To help, below is a list of frequently asked questions about custom urethane products with answers provided by the experts at PSI Urethanes.
Durometer is the hardness of a non-metallic product or the gauge used to measure the hardness. The two most common elastomer durometer scales, using slightly different measurement systems, are the ASTM D2240 type A and type D scales. The A scale is for softer urethanes, while the D scale is for harder ones.
The two main types of Polyurethanes are Polyester and Polyether. Each offers its own performance properties.
A chemical building block that provides good resistance to solvents as well as good mechanical properties in the final elastomer.
A chemical building block sometimes used in place of polyester that provides exceptional resilience and hydrolytic (reaction with water) stability.
The isocyanates most commonly utilized in polyurethane formulations are TDI and MDI. TDI stands for toluene di-isocyanate and MDI stands for methylene di-isocyanate. Both TDI and MDI urethanes are used in a variety of fields, each is best suited for specific applications.
Methylene Di-isocyanate; A base form of urethane resin that needs non-Moca Type curatives.
Toluene Di-isocyanate; A base form of urethane resin that needs Moca Type curatives.
The main difference between thermoplastic polyurethane and thermoset polyurethane is based on the physical properties of the polyurethanes. Due to their unique properties, each is best suited for specific applications.
The specific gravity for thermoset urethane is split between Polyester and Polyether; Polyester is 1.2 and Polyether is 1.1.
Yes, urethane can be machined. Typically harder polyurethane is recommended if the final product is to be machined. Anything 70 shore A and above is preferred but we have seen urethane machined in softer durometers. This would require special methods.
The following guide can be used to select the material most appropriate for your application.
| Property | Greatest | Least |
| Tensile (tension) Strength | Polyester | Polyether |
| Tear Strength | Polyester | Low Cost Polyether |
| Compression Set | TDI | MDI |
| Rebound | MDI Polyether | TDI Polyester |
| Low Temperature Properties | MDI Polyether | TDI Polyester |
| High Temperature Properties | TDI | MDI |
| Abrasion Resistance: Sliding Impingement (colliding) | Polyester MDI Polyether | Low-Cost Polyether Low-Cost Polyether |
| Heat Buildup | Polyether | Polyester |
| Hydrolysis (reaction with water) Resistance | MDI Polyether | TDI Polyester |
| Oil Resistance | Polyester | Polyether |
| Heat Aging | Polyester | Low Cost Polyether |
The chart below highlights several differences between thermoset polyurethane and thermoplastic urethane products.
| Property | Thermoset Polyurethane | Thermoplastic Urethane |
| Heat Resistance | Holds up in temperatures of up to 250° without issue | Will soften, deform and degrade at higher temperatures |
| Hardness | Wide range of durometers available in “A” & “D” scale | Very small range in “A” scale only |
| Load Bearing Capacity | Ability to hold a great amount of weight per square inch | Unable to hold a great deal of weight without destroying material |
| Abrasion Resistance | Best for abrasive applications because of its high abrasion resistance and cut resistance | Will abrade and tear in these cases |
As you can see, there is a remarkable range of urethane physical properties to choose from allowing urethane to be used across a wide variety of applications and industries.
For more information on the physical properties of urethane, be sure to check out the urethane technical brief or contact PSI today.
Contact us today to learn how we can meet your project’s requirements.
