Rheological characterization of PVC corncob composites. Effect of molecule weight of PVC

Abstract

The flow behaviors of different poly (vinyl chloride) and corncob flour composite were characterized using a Göttfert 20 extrusion rheometer. The rheological characterization includes extrusion experiments at different temperatures and screw speeds. By evaluation of flow rate and die pressure the flow properties and the activation energy of the flow can be determined. This also provides insight into the internal structure/organization of the prepared composite and gives information about process ability and processing window parameters. The flow of the melt is mostly determined by the molecular weight of the polymer but for PVC the higher organization of the polymer as tertiary and quaternary structures have also a significant effect. Moreover, the molecular weight affects not only the viscosity but also the relaxation times. This flow behavior of the polymer has changed significantly by shearing time and thermal history of the materials. PVC composites compounded from raw PVC powder of various K-values (molecule weight) were prepared and examined via a complete rheological analysis. The PVC composite's morphology mostly depends on the concentration of the components, the material matrix and the corncob additive. The viscosity of the composites, the Rabinovich exponent, and flow-viscosity curves were determined in this paper. The results of the rheological tests can help us to make comprehensive conclusion about the composite structures, processing possibilities and applicability.