Elastic properties of random-linked cis-PB networks: A characterization and gel point study

cis-Polybutadiene networks with microstructure 98% cis, cross-linked in the bulk state by gamma irradiation, were characterized in terms of their mechanical properties. Data from stress-strain analyses, swelling degrees, stress relaxation, and random-linking theory are in accordance and the estimated gel points practically coincide. Trapped entanglements lead to a 30% increase in the network modulus, from which also the plateau modulus, 0.71 ± 0.09 MPa, was determined. The tensile data were obtained from Mooney-Rivlin representations without junction constrained corrections. Preliminary stress-relaxation experiments indicated a slow relaxation at room temperature. It can be concluded that the assumption of additive contributions from chemical and entanglement cross-link densities in the Langley theory works well in the range of doses investigated here. © 1993 John Wiley & Sons, Inc.