EFFECT OF CHAIN ENTANGLING IN CROSS-LINKED ELASTOMERS.

Chain entangling is responsible for the rubber-like properties of uncross-linked elastomers in the rubber plateau zone. Whether chain entangling also contributes to the elastic properties at elastic equilibrium is still an open question. In ordinary rubber networks, chemical cross-links and entanglements act in parallel. Introduction of cross-links in the strained state produces a composite network for which the entangled network and the cross-linked network have different reference states, allowing an experimental separation of the effects of chain entangling and cross-links. Chain entangling contributes much more to the modulus than chemical cross-links for polybutadiene at typical cross-link densities.