End pressure effects of polypropylene composites reinforced with multi-walled carbon nanotubes in capillary flow
The influence of the size and content of multi-walled carbon nanotubes (MWCNTs) on the end pressure effects of polypropylene (PP) composite melts during capillary extrusion flow was investigated, with the test temperature varying from 190°C to 230°C and apparent shear rate ranging from 50 s−1 to 3000 s−1. The results showed that the end pressure drop increased with increasing apparent shear rates, while decreased with increasing test temperature, and the sensitivity of the end pressure drop to apparent shear rate for the composites was higher than that for the unfilled PP. The end pressure drop increased with increasing weight fraction and the specific surface area of the MWCNTs. The end pressure drop increased almost linearly with increasing the aspect ratio of the MWCNTs. Moreover, the end pressure effect mechanisms of the composite melts during a capillary extrusion flow were discussed.