Posted on: 26th Jul 2021
Polyurethane is one of the most commonly used engineering plastics in injection and cast moulding due to its overall excellent mechanical performance and versatility.
“Polyurethane (PUR and PU) is a polymer composed of organic units joined by carbamate (urethane) links. While most polyurethanes are thermosetting polymers that do not melt when heated, thermoplastic polyurethanes are also available.
Polyurethane polymers are traditionally and most commonly formed by reacting a di- or triisocyanate with a polyol. Since polyurethanes contain two types of monomers, which polymerise one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make polyurethanes contain, on average, two or more functional groups per molecule.”
Source – Wikipedia https://en.wikipedia.org/wiki/Polyurethane
Polyurethane’s key characteristics include toughness, flexibility, and resistance to abrasion. Significant other characteristics include extremely high flex-life, high load-bearing capacity and good resistance to weather, ozone, radiation, oil and most solvents.
Two of the main classes of polyurethane are Ester and Ether.
These two different chemical options each have their own have specific qualities and characteristics making them more, or less suitable to specific application requirements or environmental conditions.
In the material selection process, it is crucial to understand both the application of the component and the chemical composition of the material, in order to select the material best suited characteristically.
This should form part of your initial discussions. A considered approach at this early stage can prevent failures, breakdowns, down time, and subsequent cost implications further down the line.
Below we compare the mechanical properties of both material classes.
|Heat Resistance||* Higher operating temperature stability.|
* Greater resistance to heat aging.
|*Less susceptible to heat build-up.|
* Lower heat resistance in general
|Low Temperatures||* Loss of flexibility at lower temperatures.|
* Will become brittle quicker.
|* Maintains flexibility at lower temperatures.|
* More resistant to environmental changes.
|Abrasion Resistance||* Excellent surface resistance.|
* Suited to sliding abrasion applications.
|* Excellent impingement abrasion resistance.|
* Ideally suited for shot blast applications.
|Resilience & Rebound||* Excellent shock, vibration, and energy absorption. |
* Ideally suited for damping applications.
|* Lower energy absorption.|
* Higher rebound properties.
|Hydrolysis and Chemical Resistance||* Higher chemical and oil resistance.|
* Lower hydrolysis resistance.
|*Excellent hydrolysis and microbial resistance.|
*Ideal for water-based applications.
|Cut & Tear Resistance||* Higher tensile strength.|
* High cut and tear resistance.
|* Lower tensile strength.|
* Lower cut and tear resistance.
Both polyester and polyether can be manufactured in a wide range of shore hardness and colour. They can also be combined with specialist additives for specific application requirements including, flame retardent, UV stabiliser, anti-microbial and metal detectable, amongst others.
Please use this information for general comparisons only. Final product testing is always recommended.