Elastomers are polymers which have properties that are elastic, meaning they return to their original shape after being manipulated. The word comes from elastic polymer. In most instances, they are rubbers but can be other materials. Those that melt when heated are referred to as being thermoplastic. Their manufacturing applications are explored below.
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Materials and Properties
Elastomers are long-chained molecules that are irregularly coiled. When force is added they straighten out in the direction of the force, but once the force has been removed they immediately return to their coiled position. These are amorphous polymers with segmented motion. Their chains are made up of many monomers consisting of carbon, hydrogen, oxygen and occasionally silicon atoms.
Most elastomers are thermosets and require curing. This can be done through application of heat, irradiation or a chemical reaction. The long polymer bonds are cross-linked by covalent bonds, so after curing they are stronger and cannot be remoulded or reheated. Those that are thermoplastic can be melted into a liquid state and become brittle when cooled. The polymer chains in this instance are cross linked with weaker bonds such as hydrogen. Those that have covalent cross bonds can be extended by up to 700 percent, those with weaker bonds may be permanently damaged with applied pressure.
The temperature of the polymer affects its elasticity. Those that have been cooled to glass or crystalline will have less mobility in their chains and, therefore, less elasticity. Those that have been heated to a higher temperature will have higher mobility and will be malleable. Those left at an ambient temperature will be soft and deformable. If a polymer crystallises at room temperature, it would be too brittle to have any uses as a flexible and extendable material.
Examples
The most common examples of elastomers are rubbers such as natural rubber and butyl rubber. Thermoplastic elastomers include elastron and elastin. Both natural and synthetic rubbers have many applications, including for a silicone hose manufacturer such as Goodflex Rubber. They’re used extensively in the manufacture of tyres. They can also be used for tubes, including medical grade, which are used heavily in the medical and pharmaceutical industries. Other uses include gloves, balloons, rubber bands and pencil erasers.
Thermoplastic elastomers are used primarily in manufacturing processes including injection moulding. Polyurethanes are used for foams, seals and for carpet underlay.