Quantitative Study of Extrudate Swell for Polymer Blends

The extrudate swelling of blends was analyzed quantitatively. The extrudate swell ratio could be predicted from its apparent constitutive parameters and processing conditions (length-to-diameter ratio in capillary, shear rate and temperature). More importantly, it was first suggested that there is one exponential multiplication correlation between blend swell ratio and those of components. This relation was found when considering one component acted as the filler of the other in blend as in composites, in which composite swell ratio was usually reduced from that of the matrix by one concentration shift factor. In contrast, the blend swell ratio exhibited positive derivation against of linear addition of the component swell ratios against the negative derivation in viscosity. The swell ratio data were chosen to verify the theory from publications for incompatible blends. The good agreement of predicted swell ratio with the experimental data confirmed the feasibility of the model in analyzing the swelling behavior of blends.