CONTRIBUTION OF ENTANGLEMENTS TO RUBBER ELASTICITY

Uncrosslinked polymers show rubber-like properties above the glass transition temperature and at times short enough to prevent flow. This effect is thought to be due to a temporary entanglement network. Several studies indicate large entanglement contributions to the equilibrium elastic modulus of crosslinked networks. Three methods are discussed in greater detail: stoichiometric crosslinking with a suitable peroxide, the Langley method, and the two-network method. The two latter methods give equilibrium entanglement modulus contributions which are equal to the pseudo-equilibrium modulus of the uncrosslinked polymer. They also indicate that the entanglement contribution to the stress is responsible for departures from neo-Hookean behaviour observed in simpler extension. © 1979.