On the molecular weight dependence of slip velocity of polymer melts

Theoretical models regarding the slip of polymer melts are compared with the experimental results of several researchers on the basis of the molecular weight (M-w) dependence of the slip velocity (V-s). Using simple assumptions, it is shown that agreement between theory and experiment can only be achieved if the models are adjusted to address the random adsorption density of polymer chains on high energy surfaces and the stiffness of the adsorbed chains as assessed by the molecular weight of entanglements. With respect to adsorption density, the transition from the mushroom to the overlap regime results in the development of interactions between adsorbed chain segments which changes the V-s-M-w scaling. As these interactions involve mutual entanglements, their development is hindered by the stiffness of the adsorbed chains. Accordingly, a novel regime within the overlap regime is proposed to exist, observed when the segments of the adsorbed chains are not flexible enough to interact with the neighboring chains. (C) 2017 The Society of Rheology.