Chain Anisotropy Effect on Polymer Nonlinear Viscoelasticity

Measurements of shear dynamic modulus have been made on the polybutadiene samples firstly cross-linked partly followed by the second cross-linking in large extension. The polymers prepared in this manner were expected to keep anisotropic chain configuration. The polymers showed different behaviors in G′ and tanδ from those cross-linked at no deformation. The former polymers showed lower values of G′ and higher values of tanδ than the latter polymers. The deviations became large with increase in degree of extension. It may be concluded that chain anisotropy is really one of the origins for nonlinear viscoelasticity of polymers. It lowers the energy storage term and raises the energy loss term.