Rubber is made from the latex (milk of the Evergreen Forest tree). It is an elastomer, a polymer which regains its original shape and possesses high elasticity. It is a tough polymer which has high resistivity to withstand the weather and chemical attacks.
Types of rubber
Rubber can be categorized as natural rubber, or synthetic rubber. Many substances, such as butyl rubber, Thiokol, or neoprene are used as synthetic rubber. An elastomer must have high molecular weight and a flexible polymer chain.
Natural rubber is one of nature's unique materials founded by Christopher Columbus's. Before that the Indians use to make balls of rubber by smoking the milky, white latex of trees of the genus. Later it was used in waterproofing shoes, garments etc. Crude rubber possessed the properties of elasticity, plasticity, strength, durability, electrical non conductivity, and resistance to water. The other name of natural rubber was “gum- elastic”.
The first commercial use of natural rubber was as a waterproofing material. Later on it was used for moulding. The major use of natural rubber was made in weaving waterproof garments in which a thick coal tar naphtha solution of rubber was used.
Crude rubber is basically a hydrocarbon having the chemical formula C5H8, along with 2 to 4 percent protein and 1 to 4 percent acetone-soluble materials (resins, fatty acids, and sterols). According to Faraday's analysis natural rubber is obtained from the pure monomer, which he named isoprene .The molecular weights of rubber molecules range from 50,000 to 3,000,000. Sixty percent of the molecules have molecular weights of greater than 1,300,000.
The natural rubber is thermoplastic in nature and becomes soft and sticky in summer and hard and brittle in winter. This problem encouraged scientists for further developments.
A sample of rubber mixed with sulphur and litharge (lead oxide, PbO) on a hot stove gave birth to rubber like material which is heavily cross-linked, insoluble, and infusible, thermosetting polymer or "thermoset." The process is called "vulcanization". Later on sulphur to convert natural rubber into ebonite, the first thermosetting plastic.
The development of a synthetic rubber was a slow process and it was used in more quantity.
Other Synthetic Rubbers
Although natural rubber performs well for most uses, some of the newer synthetics are superior to it for specialized purposes. Today rubber is indispensable for a variety of products and industries, and our modern world, with its many necessities and luxuries, would be unthinkable without it.