Elastic properties of real elastomers at small deformations

Elastic properties of real elastomers were examined by using partial derivatives of the strain energy density function (W) with respect to the invariant (I i , i=1,2,3) of deformation tensor. The values of the derivatives at zero strain limit for styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR) and butadiene rubber (BR) were compared with those derived from the theory shown in the previous paper, where compressibility of the materials was taken into account. The asymptotic behavior of the derivatives for isoprene rubber (IR) and segmented polyurethaneurea (SPU) was also compared with those of the three types of rubbers. It was shown that the theoretical predictions for the limiting value agreed fairly well with the experimental values of the elastomers.