Stress-strain behavior of segmented polyurethaneureas under pure shear deformation

Elastic properties of segmented polyurethaneureas (SPUs) under pure shear deformation were investigated. Data were analyzed by using strain energy density function (W). The values of the derivatives of W with respect to the invariants of the strain tensor (I_i; i = 1, 2, 3 ) at zero strain limit were also estimated theoretically and were compared with those estimated by experiment. The limiting value of the derivative with respect to I₁ (W/I₁) was shown theoretically to be 5 G/8, while the derivatives with respect to I₂ and I₃ (W/I₂ and W/I₃ were respectively-G/8 and -3G/8. The theoretical prediction could explain the asymptotic behavior of the derivatives of SPUs as well as isoprene rubber (IR) reported by Kawabata et al. at small I₁ limit.