What is rubber? The formula of rubber? What are the physical and chemical properties of rubber?
What Are The Properties of Rubber?
RUBBER; a term applied to a wide variety of elastic substances which are obtained from a great number of trees, shrubs, and vines, including the Hevea brasiliensis (the major commercial source), Castilloa (Castilla) elástico, Manihot Glaziovii, Funtumia elastica, kok-saghyz, Landolphia, guayule (Parthenium argentatum), and others. The rubber hydrocarbon itself is suspended or dispersed in a milky liquid (latex) which occurs in the inner bark of the branches and trunk of the rubber trees, and to a lesser extent in the leaves and roots. When isolated in its pure state, the rubber hydrocarbon is essentially a polymer of isoprene as represented by the chemical formula .
Properties of Rubber. As has been noted, the term rubber can be applied to the elastic, resilient, coherent solid obtained from the latex of many varieties of trees, plants, and shrubs. Rubber is to the rubber manufacturer what flour is to the baker. It is a basic raw material to be modified and processed in thousands of ways to meet any requirement. It can be made to wear out quickly like an eraser or to withstand the roughest kind of abrasion as in a tire tread. It can stretch like a rubber band or be as inelastic as a bowling ball. It can be an electrical insulator or an electrical conductor. It can be soft and foamy as in a mattress or tough enough to put an edge on carbon steel as in a rubber-bonded grinding wheel.
The name may be applied to the material in its crude form, or to compounds mixed with sulphur and other ingredients, or to finished products. Of little commercial value in its crude form, rubber becomes one of the most valuable materials of our modern day-to-day existence when compounded and vulcanized. It is soluble in naphtha, carbon disulphide, carbon tetrachloride, turpentine, ether, gasoline, benzene, and similar solvents.
Among the more important physical properties of rubber are softness, toughness, elasticity, impermeability, adhesion, and electrical resistance. The outstanding property which distinguishes it most from all other materials, including the synthetic rubbers and the rubberlike materials, is that when repeatedly stretched to many times its length it will come back approximately to its original dimensions.
Vulcanized rubber possesses widely varying characteristics of elasticity, softness, or hardness, depending on the amounts of sulphur and on other factors which will be described later. In the vulcanized state it is less affected by heat or cold than in the unvulcanized state. For commercial purposes rubber can also be made highly resistant to abrasive wear, flexible or extensible, waterproof, relatively impermeable to gases, an electrical and heat insulator, resistant to the action of all but a relatively few chemicals, and with high frictional resistance on dry surfaces and low resistance on surfaces wet with water.