Elasticity of rubber - Assignment Example

Download file to see previous pages Rubber substances are not confined to natural rubber, however. They take account of a great variety of synthetic polymers of comparable properties. An elastomer is considered as a polymer that shows evidence of rubber elastic properties, i.e. materials that can be possibly stretched to a number of times its original length without breaking and which, upon release of the stress, instantaneously returns to their original lengths. A rubber is more or less an elastic material, since its deformation is instantaneous and it further shows almost no slither (Bjork, 1988). The distinctive nature of rubbers was ascertained by John Gough in 1305, and described his findings and experiments as shown in this subsequent paragraph. A person has to clasp one end of the slip of a rubber between the thumb and forefinger of each hand; get the central point of the piece into slight contact with the lips; further lengthen the slip swiftly; and you will instantly make out a feeling of warmth in that section of the mouth that is in contact with stretched rubber. For this resin evidently grows warmer the further it is lengthened; and the edges of the lips possess a higher degree of sensibility, which facilitates them to discover these changes with greater facility than other parts of the body. The augment in temperatures, which is recognized in the event of extending any pieces of Caoutchouc, may be obliterated in on the spot, by allowing the slip to contract again; which it will do quickly by desirable quality of its own spring, as soft as the stretching forces cease to act as soon as it has been fully exerted. Gough made these comments regarding his second experiment: In any case one end of a slip of Caoutchouc is fastened to a rod of wood or metal, and some weight is fixed (added) at the other extremity/end; the thong will be seen to become longer with cold and shorter with heat (Mark, 1984). To make certain this concept, it is necessary for a self experimentation. One will only need a strip of rubber, a weight and a hair-dryer. Gough presented no better explanations to the unexpected findings, such as that the expected stiffness increments with rising temperatures and that heat is progressive throughout stretching duration. It took approximately fifty years prior to the formulation of thermodynamics of the rubber elasticity. Rubbers exhibit predominantly entropy-driven elasticity through measurements of force and specimen length at varied temperature levels. Thermo-elastic effects of rubber shows that stretched rubber samples which are subjected to constant uniaxial load contract reversibly on heating, and the same sample can give out heat reversibly if stretched. These two observable concepts are true and consistent with the view that the entropy of the rubber decreased on stretching. Molecular picture of the entropic forces is dated back to the theoretical work of 1930’s, when it was suggested that the covalently bonded polymer chains had been oriented during extension (Gumbrell, Rivlin, &, Mullins, 1953, p. 1495). Methods and procedures This study involved an investigation in the thermo-elastic behaviors and thermodynamics, with regards to the energetic and entropic elastic forces. At minimum strains, characteristically less than ? = L L 0 < 1.1 (where L and L0 are the dimensions of the unstressed and stressed specimens, respectively), the stress at ...Download file to see next pagesRead More