Elastomers

Elastomer is a long chain polymer which undergoes elongation under stress. This elongation is huge but when the stress is released polymer regains its shape. Elastomers possess a linear but coiled structure. In elastomers, inter chain cohesive forces are negligible. Natural rubber, synthetic rubber, nylon etc. are elastomers. Natural rubber is obtained from rubber trees grown in tropical regions. Rubber tree stores rubber in the form of white milky fluid behind the bark of the tree. This fluid is called latex. By cutting barks carefully we can collect the latex. Natural rubber is hard and brittle at low temperatures. It becomes soft and sticky at higher temperatures. As a result of oxidization, it smells bad after a few days. Natural rubber is soluble in many organic solvents and it absorbs water. Acids, alkalis, oxidizing and reducing agents can easily attack natural rubber since its chemical resistivity is very low. Natural rubber is not at all advisable for all these deficiencies. Natural rubber has low tensile strength, low abrasion resistance and low wear and tear resistance. Synthetic rubber is preferred over natural rubber because of its outstanding properties. Buna-S rubber, neoprene rubber and butyl rubber are examples of synthetic rubber.