What Is an Elastomer: Thermoplastic and Thermoset Concepts
An elastomer is an elastic polymer material that can return to its original shape after being stretched or compressed. The vast majority of materials we call "rubber" are elastomers. In this article we explain how elastomers work and how they are divided into two main categories — thermoset and thermoplastic elastomers.
What makes an elastomer elastic
Elastomers consist of long, coiled polymer chains. When the material is stretched, these chains straighten out, and when the force is removed, they coil up again, returning to their original state. This "memory" effect is made possible by the cross-links between the chains. Without cross-links, the material would undergo permanent deformation when stretched.
Thermoset elastomers
Traditional rubber is a thermoset elastomer. Here the cross-links are formed during a chemical process called vulcanization and are irreversible. That is, once the material has hardened, it cannot be melted again or reshaped by heating. This group includes materials such as EPDM, NBR, SBR and silicone. The advantage is high temperature and chemical resistance, as well as mechanical stability.
Thermoplastic elastomers (TPE)
Thermoplastic elastomers combine both the elasticity of rubber and the ease of processing of plastic. In them the bonds are not chemical but physical in nature, and they soften when heated and harden again when cooled. This means that TPE can be melted and reshaped many times, and even recycled. The drawback is that high-temperature resistance is lower than that of thermosets.
Comparison of the two types
- Thermoset: irreversible vulcanization, high heat and chemical resistance, cannot be remelted.
- Thermoplastic: can be recycled, fast production, but the temperature limit is lower.
For industrial seals and profiles, thermoset rubbers are usually chosen, because they remain stable over a wider range of temperatures and pressures.
The main properties of an elastomer
When evaluating an elastomer, several key parameters are considered: elasticity, hardness (Shore A), temperature range, chemical resistance and shape recovery after compression. Most of these properties are adjusted by the composition of the rubber compound.
If you want to know which type of elastomer suits your needs, see our product range or contact us for technical advice.