Melt Flow Instability Of LLDPE And Its Composites

Oscillating flow is one of the most important instability phenomena in capillary flow.Although the melt flow instability had been theorized by Weill since l980,the entrance pressure instability has not yet been studied experimentally.Hereby,In this study the melt flow instabilities of LLDPE and its composites with different dimensions carbon fillers(Multi Wall Carbon Nanotubes(MWCNTs),thermally reduced Graphene(TRG)and Carbon Black(CB))had been investigated.Bagley correction and zero length die were applied to calculate the instability of entrance pressure drop in capillary flow.In order to obtain the relatively accurate curve of entrance pressure drop,distinctions of the entrance pressure drop and extensional viscosity,which calculated by the two methods were compared and the inner mechanism of these differences were analyzed deeply.The entrance pressure fluctuation of LLDPE was clearly observed during the extrusion process,which was revealed to closely correlate with extrudate distortions.The origin of entrance pressure fluctuation had been revealed via the polymer chains entanglement-disentanglement model.The different dimensions carbon fillers which dispersed in the polymer matrix also had an important impact on the melt flow form.Such influence always associated closely with the movement of fillers and the interaction of polymer chains.