Rubber

F.A.Q.

WHAT ARE THE PROPERTIES OF ELASTOMERS?

Elastomers have the following properties:

- rubber-elastic

- non-meltable

- not soluble

- no thermoplastic properties (exception: thermoplastic elastomers)

Thus, the rubber elasticity of elastomers is a very special property, which is based on a static-dynamic equilibrium between order and entropy.

But what is the exact cause of the elastic property of elastomers?

In the unstretched normal state, the polymers of elastomeric plastics are in the form of a tangle - that is, a "disordered" state of entropy.

However, because the macromolecules are widely cross-linked, they can be stretched by the application of force - to twice their normal length. Now the entropy decreases. The polymers must therefore give up their entropy-rich state again and arrange themselves in a stretched state.

If the force is now released, the elastomers return to their original normal shape, since they always strive for entropy. This interesting process is also known as rubber elasticity.

WHAT TYPES OF ELASTOMERS EXIST?

Plastics are divided into three categories based on their different physical properties: Thermoplastics, Thermosets and Elastomers.

Although elastomeric plastics are solid in shape, when they are subjected to tensile or compressive stress, they can deform elastically - up to twice their actual length. However, elastomer plastics then return to their original shape.

These chemical properties make the material so versatile and indispensable in use.

Elastomeric plastics can be categorized based on both the results of the vulcanization process and their thermal properties.

Elastomers are divided into two distinct groups: Natural Rubber and Synthetic Rubber. Both types are created through the process of vulcanization, which is responsible for the elasticity of elastomers.

Vulcanization creates sulfur bridges between the linked macromolecules of the elastomers. The remaining reactive double bonds must now be protected from oxygen and strong UV radiation. Carbon black, zinc oxide and other stabilizing fillers are therefore incorporated. This prevents the polymers from sliding past each other under stress.

The vulcanizates of elastomers are both natural rubber and synthetic rubber.

Elastomers, however, can also be classified according to their thermal properties, which depend on the temperature involved. While the typical elastic state of elastomers exists only at room temperature, plastics exhibit different properties at low and high temperatures.

At very low temperatures below the glass transition point, elastomers become brittle as well as glassy and the mobility of the molecules decreases. This state is therefore referred to as the hard-elastic state.

A very high temperature, however, causes the elastomers to be destroyed by thermal decomposition - as is the case with all plastics. The rubber elasticity of these so-called thermoelastics or thermoplastic elastomers is above the 20-degree mark and extends to thermal decomposition.

Thermoplastic elastomers are meltable and easier to process.  However, according to DIN standards, they do not count as elastomers and tend to have the properties of thermoplastics.

FOR WHICH APPLICATIONS ARE OUR ELASTOMERS SUITABLE?

Elastomers can be used universally. They are mainly used where strong elastic properties of plastics are required. Quite typical, therefore, is the use of elastomers in the manufacture of tires, seals (for example, O-rings) and rubber belts.

However, conveyor or assembly belts, such as the suitcase conveyor at the airport or the supermarket checkout conveyor, are also an important area of application for elastomers.

We at TER Chemicals have recognized that increasing application temperatures as well as the addition of additives, carbon blacks and resins are constantly producing new formulations of elastomeric plastics. Therefore, elastomeric materials are indispensable in the industry and we also have a strong interest that this type of plastics should be continuously improved and developed.