Possible role of force balance on entanglements

The usual assumption of affine deformation of the strands of a polymeric ne twork appears not to fulfil force balance over the nodes of the network in case such nodes are entanglements. In an effort to improve over the classic al theory of Doi and Edwards for entangled polymers, a simple model is here proposed which is so constructed as to obey force balance. Explicit predic tions for step strains are here obtained which compare very favourably with data, not only of damping function, but also of normal stress ratio.