Relationship Between Morphology And Rheology Of In-situ Microfibrillar Polypropylene Blends Prepared By Different Flow Fields

As one of the most important methods to increase the mechanical properties of polymer, in-situ fibrillation has attracted a great deal of interests. In this study, poly(butylene succinate)/polypropylene (PBS/PP) and low density polyethylene/polypropylene (LDPE/PP) in-situ microfibrillar blends are prepared in different fluid fields using a single screw extruder, and the relationship among the fluid field, morphology, and rheological properties is studied.PBS/PP (85/15 w/w) in-situ microfibrillar blends are prepared using a single screw extruder equipped with a slit die, which provides a shear mixing field. The results show that the average diameter and amount of PP droplets decrease, the average diameter of PP fibres decreases and their amount increases as the processing temperature decreases. The average diameter of PP fibres decreases and their amount increases as the screw speed increases. The PP droplets in the blend prepared at die temperature of 170℃and screw speed of 80rpm have a minimal average diameter, which is 2.98μm.PBS/PP (85/15 w/w) blends are prepared along a single screw extruder with a shear mixing field and chaotic mixing field, respectively. The results show that it can form smaller average diameter of PP fibres, higher dispersion parameter of PP particles, and lower fractal dimension of PBS/PP blends using the later extruder. Complex viscosity, storage modulus, and loss modulus are increased as PP concentration increases. The storage modulus and loss modulus of PBS/PP blends near the die exit prepared by the extruder with the chaotic mixing field at screw speed of 50rpm present a solid-like response at lower frequencies. It means that PP forms network structure.LDPE/PP (90/10, 80/20, and 70/30 w/w) blends are prepared using a single screw extruder plus HP extruder. The results show that PP can not form fibres with the PP concentration of 10wt%, form fibres of 1.98μm with the PP concentration of 20wt%, and form fibres of 0.69μm with the PP concentration of 30wt%. Time-temperature superposition (TTS) curve show that no phase separation appears in LDPE/PP blends. Han plots show that the size of PP becomes less homogeneous as the increaseing of PP concentration in LDPE/PP blends.