Rheology of PVC; Part IV : particulate flow

The behavior of polyvinyl chloride, (PVC), formulation changes drastically with the temperature and the method of sample preparation. In the steady state shear mode, upon a decrease of the rate of deformation, the data may show either a steady increase of the shear viscosity or leveling off to a Newtonian plateau. In the dynamic test mode, the storage modulus, G\u2032, shows a viscoelastic behavior, whereas the loss modulus, G\u2033, shows the yield. Only at temperatures above 210\ub0C are normal flow curves for polymer melts obtained. Rigid PVC wire coating formulation was examined at 140 to 220\ub0C using serrated parallel plates, 2.5 cm in diameter. The data at frequencies \u3c9 = 10\u207b\ub2 to 10\ub2 rads/s were recorded. The results were analyzed in terms of the relation, derived for polymeric composites, in which the yield stress was explicitly incorporated. It was found that G\u2033 (but not G*) could be easily understood in terms of the model, provided that the yield stress was allowed to vary with the temperature. Three distinct flow zones were observed with the two border\u2010temperatures at about 180 and 210\ub0C, assigned respectively as due to gel and crystalline melting. These findings were supported by earlier results of the dielectric measurements. In conclusion, treating PVC as a composite provides a simple and effective means of data interpretation.Peer reviewed: YesNRC publication: Ye