ON THE SMALL STRAIN BEHAVIOR OF PEROXIDE CROSSLINKED NATURAL RUBBER.

In this paper, authors present new results in which a sample of peroxide-cured NR was tested in torsion where both torque and normal thrust were measured. In this study, the strains at which the normal force was measured were lower. Authors determined the derivatives of the strain energy density function, PARTIAL W/ PARTIAL I//2, and have further confirmed the result from the prior study that for the peroxide-cured rubber systems which were freshly prepared in laboratory, PARTIAL W/ PARTIAL I//2 does not become negative, even at extremely small deformations. These results are contrary to results reported in the literature by other measurement techniques or with samples undergoing a different crosslinking (curing) history.