There exist many types of material used for various purposes. Materials are classified based on there composition, elasticity, tensile stress, temperature withstanding capacity and many more. Materials can be soft and rigid depending on their molecular composition. Some materials are rubbery and can be retained back into original shape after stretching up to a certain level or after the removal of external force.
Materials which are elastic in nature and are composed of a long chain of molecules or polymers are known as elastomers. Here the materials are irregularly coiled. Elastomers are the materials which stretch upon application of the force and retains back to original (compact) shape after the removal of the force. These materials do not undergo any permanent deformation after the application of any external force. Below figure explains how the elastomers react to the pressure/force and recoil back.
Elastomers have high yield strain and have very low Young’s modulus quotient compared to other materials. Some of the examples are natural rubber or polyisoprene, polyurethanes, polybutadiene, and polyisobutylene.
Elastomers are amorphous polymers which endure beyond the glass transition temperature. Hence we can witness a considerable segmental motion in the polymer chain and hence it is said to be permeable in nature. There exists another set of polymers known as thermoplastic elastomers which features strong intermolecular bond. If polymers feature weak interlinks, chances are high that they might give way at high temperatures. This lets the material to take a new shape in response application of external pressure. These materials can be reused and reprocessed.
The materials which are relatively soft and deformable at certain temperatures are used for manufacturing of adhesives, rubber septums, molded flexible parts, and seals.
Tensile stress comes into picture when the force applied on the body is responsible for the elongation of the material along the axis of the applied force. Ductile materials have the tendency to withstand the load while brittle materials fail before reaching the ultimate material strength. Tensile stress can be found using the below formula
A = cross-sectional area
σ = tensile stress
F = force applied
Tensile stress causes the materials to increase in their size and differs from one material to another.
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