DYNAMICS OF ENTANGLEMENTS - A NONLINEAR MODEL CONSISTENT WITH THE COX-MERZ RULE

It is argued that the flow directly contributes a mechanism by which t he topological obstacles are renewed. As a consequence, the chain diff usivity is increased (or, equivalently, the friction coefficient is de creased) in fast flows. Such a nonlinear effect is incorporated in a s imple dumbbell model so as to produce a constitutive equation in close d form. An extension to the case of multiple relaxation times is also briefly considered. The predictions compare favourably with the Cox-Me rz rule as well as with the behaviour of polymer melts in elongational flows.