Flow Behavior of Dispersed Composite Polymer Melts

Abstract

When two different polymers are mechanically blended, the flow curve of the composite melt does not always lie in between the curves for the component polymers. In order to find the condition for this phenomenon to occur, we measured the flow curves of blends of a polystyrene (PS) and a high density polyethylene (HDPE) with a Thixotrometer. Four samples of PS of various fluidities were examined. The fluidity of HDPE was higher than any PS samples at the temperature of measurements, 200°C.
When the fluidity of PS was very low and much apart from that of HDPE, the flow curves for the blends lay between those of PS and HDPE at any blend ratio. As the fluidity of PS increased and approached that of HDPE, the flow curve for the blend of high PS content, i.e., 0.75, became to intersect that for the PS; the blend exhibited a fluidity lower than even the component PS at low rates of shear. In the case of the PS of the highest fluidity, the blend of high PS content exhibited fluidity lower than the PS over the whole range of rate of shear studied. These results were discussed in terms of a proposed phenomenological blending law.