Microstructure evolution and mechanism of PLA/ PVDF hybrid dielectrics fabricated under elongational flow

Abstract Polylactide (PLA)/polyvinylidene fluoride (PVDF) hybrid dielectrics with high melt flow index ratio have been prepared by a novel twin-eccentric rotor extruder (TERE). In TERE, the continuous elongational flow, originated from the alternate compression and release, plays a key role during melt blending. Compared to traditional shear flow, it facilitates the dispersion and orientation of the dispersed phase along the elongational direction, forming the fine and anisotropic micromorphology in PLA/PVDF blends. With the change of composition ratio, twice phase transitions and three structure regions are observed, in which the interpenetrating network structure is formed at 60-70 wt% PVDF loading. Based on the coupling effect of elongational flow and material properties, the mechanism of microstructure evolution for PLA/PVDF blends is put forward. In addition, the effective dielectric constant of PLA/PVDF blends is slowly and then rapidly improved in linear with PVDF content increasing. The turning point is the first phase transition due to the formation of new continuous phase of PVDF.