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.
Polyester versus Polyether
The two main types of Polyurethanes are Polyester and Polyether. Each offers its own performance properties.
What is Polyester?
A chemical building block that provides good resistance to solvents as well as good mechanical properties in the final elastomer.
What is Polyether?
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.
What is MDI?
Methylene Di-isocyanate; A base form of urethane resin that needs non-Moca Type curatives.
What is TDI?
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.
What is the specific gravity for thermoset urethane?
The specific gravity for thermoset urethane is split between Polyester and Polyether; Polyester is 1.2 and Polyether is 1.1.
Can you machine polyurethane?
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.
What polyurethane material would work best for my application?
The following guide can be used to select the material most appropriate for your application.