Polyurethane Elastomers are extremely versatile materials and this has been the key to their widespread applications. This flexible engineering material is available in sheet, rod and custom cast products.
Polyurethane has a unique design and construction combining many of the advantages of rigid plastics, metals and ceramics with the extensibility of rubber.
One of the easiest ways of categorizing polymers is through hardness. The equipment used to test this is known as a Durometer, which basically indents the sample with a needle. The amount of indentation move then reflects the hardness of the sample. The most common scales used for hardness are Shore A for most elastomers and Shore D for high hardness elastomers.
There are many different types of Polyurethanes. The four basic types are:
- POLYETHER /TDI
- POLYETHER / MDI
- POLYESTER /TDI
- POLYESTER / MDI
As a general guide to Polyurethane:
Polyethers are recommended for applications were parts undergo dynamic stress. (ie. They incur lower heat build-up. They also have advantages in resilience, low temperature performance and resistance to water attack).
Polyester based urethanes have superior cut, tear, abrasion, oil and solvent resistance.
MDI based products have lower isocyanate odour than similar TDI types and have superior hydrolysis resistance and higher resilience.
TDI based products are less sensitive to moisture, have shorter demould times and lower cure temperature requirements compared to MDI types.
Polyurethane can be adapted to comprise a wide range of unique properties, which is a key factor of its versatility. These factors include:
- Abrasion resistance
- Toughness – Tensile strength
- High load bearing ability
- High tear resistance
- Mechanical properties
- Resistance to water, oil, grease
- Electrical properties
- Corrosion resistance
- Colour range
- Cost effectiveness (when long service life of PU par solutions)