ELASTIC PROPERTIES OF RANDOM-LINKED CIS-PB NETWORKS - A CHARACTERIZATION AND GEL POINT STUDY

cis-Polybutadiene networks with microstructure 98% cis, cross-linked i n the bulk state by gamma irradiation, were characterized in terms of their mechanical properties. Data from stress-strain analyses, swellin g degrees, stress relaxation, and random-linking theory are in accorda nce and the estimated gel points practically coincide. Trapped entangl ements lead to a 30% increase in the network modulus, from which also the plateau modulus, 0.71 +/- 0.09 MPa, was determined. The tensile da ta were obtained from Mooney-Rivlin representations without junction c onstrained corrections. Preliminary stress-relaxation experiments indi cated a slow relaxation at room temperature. It can be concluded that the assumption of additive contributions from chemical and entanglemen t cross-link densities in the Langley theory works well in the range o f doses investigated here.