NETWORK STRUCTURE AND MECHANICAL-PROPERTIES OF ELASTOMERS .1. CHARACTERIZATION OF NETWORK DEFECTS IN UNFILLED RUBBERS

A network model is introduced that allows a characterization of unfilled, amorphous rubber networks by uniaxial stress-strain measurements at large extensions. The influences of topological constraints, finite extensibility and network defects, like trapped entanglements and dangling chain ends, as well as main-chain scission effects are considered. These influences are demonstrated by comparing thiuram- and peroxide-cured NR-networks. It becomes obvious that the relatively low topological constraint contribution (C2-term of the Mooney-Rivlin equation) found for the peroxide-cured networks is related to a lower trapping rate of entanglements, which results from main-chain scission during the curing procedure.