Effect of cross-linking density on dynamic mechanical properties of polynorbornen compounds

The effect of cross-linking density on dynamic mechanical properties of polynorbornen (PNR) sheets containing an aromatic process oil was investigated. The mechanical loss tangent (tan delta) and loss modulus (E ''), measured as a function of temperature, had a single peak corresponding to alpha dispersion. The increase in the cross-linking density remarkably shifted the tan delta and E '' peaks to the higher temperature side, while the peaks became broader and the peak value of tan delta notably decreased. The temperature of tan delta peak had an Arrhenius type frequency dependency, and the activation energy increased with increasing density of cross-linking. The equation of Sichina well predicted the peak temperature of tan delta, using T-g from DSC and the activation energy. The tensile strength increased linearly with increasing cross-linking density.