Why use polyurethane?
A tough, resilient material, polyurethane can outperform rubber for abrasion resistance. Polyurethane can be injection moulded, into most shapes. Polyurethane is a very tough elastomeric plastic, combining all of the best features of both rubber and plastic.
The major benefits of polyurethane?
Polyurethane can be formulated to possess superior properties in the following categories:
- Outstanding high wear abrasion resistance
- Good low temperature flexibility and impact resistance
- Good hydrolytic stability
- Low compression set
- High compressive strength
- Low gas and vapour permeability, relatively high moisture vapour transmission rates
- High resistance to oils, greases, oxygen and ozone
- Ability to be painted without primers
- Low extractable levels
- Good Load bearing capacity, tear resistant, damping abilities, control shock, and lessen noise and vibration in the most arduous conditions.
What are the service temperature limitations of polyurethane?
Depending on the formulation, polyurethane will stay flexible at temperatures from as low as minus 60 degrees Celsius to as high as 80 degrees Celsius – if not higher. Special formulations can extend this to around 135 degrees Celsius in some cases. (Like Eurothane HT193 ACC2 High Temperature Polyurethane)
What is Shore hardness?
Shore hardness is a measurement of the resistance of a material being penetrated by a needle under a defined force. It is determined as a number from 0 to100 on the scale A or D. The letter A is used for flexible types and the letter D for rigid types, although the Ranges do overlap.
Polyurethane is available in a range from 60 Shore A up to 75 Shore D according to DIN53505 (ISO868).
Tear resistance of polyurethane?
In this area polyurethane is far superior to most other plastics and rubbers. The test is conducted to DIN 53515.The sample is stretched at right-angles at a rate of 500mm/min until tear. The tear resistance Kn/m is the ratio between maximum force and the sample thickness.
Polyurethane will eventually wear out, but most TPU’s are considered to be the most abrasion resistant elastomeric material available.
Is it brittle?
No. Polyurethanes will withstand severe shock and impacts.
- Common solvents have less effect on polyurethane than they do on many synthetic rubbers.
- Polyurethane is resistant to short–term contact with most common acids and up to 50% concentration of most alkalis has little or no effect at room temperature.
- Polyester based TPU’s under certain climatic conditions are liable to Microbiological attack by certain enzymes. This type of attack initially becomes visible as discolouration. Polyether based TPU’s are resistant to micro-biological attack and hydrolysis
- Polyurethane exposed to lengthy periods of hot water, moisture vapour or tropical conditions will cause an irreversible break down of the polyester chains through hydrolysis. Polyether-based polyurethane is much more resistant to hydrolytic degradation.
- Polycaprolactones based polyurethanes have increased resistance to hydrolysis.
Lubricating oils and greases?
Polyurethane is more resistant than most elastomers but compatibility testing of lubricants would be recommended.
Will it bond with metal?
Yes. An excellent bond is obtainable to all common metals.
What are environmental concerns with using polyurethane materials?
Polyurethanes do not break down easily, and their lifetime of service is often quite long. When disposed of they will biodegrade extremely slowly, but it is unlikely that they pose a toxic risk in a normal disposal manner.
How does polyurethane compare in cost to other materials?
Polyurethane costs more per unit weight than high volume utility plastic materials, but it offers far higher properties in many areas. It doesn’t make sense to use polyurethane in instances where it provides no performance advantages.