Study On The Preparation Methods Of Carbon Nanotubes Filled Poly (Vinylidene Fluoride) Composites

At present, carbon nanotubes/polyvinylidene fluoride (MWNTs/PVDF) composite materials have a very attractive application prospect in the field of sensors, energy and biological materials. However, their research level is still in the laboratory stage, without large-scale industrial applications. Further study on the microstructure and properties of MWNTs/PVDF composites under different experimental conditions has a positive significance for promoting its theoretical study and accelerating the practical application.In this paper, MWNTs/PVDF composites were used as the research objects to explore the effects of the process conditions on the dispersion of carbon nanotubes and the macroscopic properties such as conductivity, mechanical properties, thermal conductivity and tensile properties of the composites. The effect of tension on the orientation of carbon nanotubes, conductivity and dielectric properties of composites was also carried out. The effects of rotor speed and rotor structure on the mixing characteristics of twin rotor continuous mixer were investigated by numerical simulation; Carbon nanotubes/poly (vinylidene fluoride) composite materials with different process conditions were preparated by continuous mixing experiment platform; The mechanical properties, electrical properties, rheological properties and micro-morphology of the composites were characterized by means of cone-plate rheometer, universal mechanical testing machine, SEM and high impedance meter; The effects of mixing flow field characteristics, mixing process and post-treatment on microstructure and macroscopic properties of the composites were analyzed and discussed. The main results are as follows:(1) The rotor speed is one of the main factors affecting the performance of MWNTs/PVDF composites. Within a certain range, with the increase of the rotor speed, the shear stress of the polymer flow field to the carbon nanotube aggregates increases, which leads to better dispersive of carbon nanotube and lower volume resistance and better mechanical properties of composites. When the rotor speed is too high, the depolymerization and stretching of the mixing flow were too strong, which influence the dispersed phase to form an effective communication structure in the matrix material and the dispersion effect of carbon nanotubes is not obvious. Therefore, the appropriate increase of rotor speed for the preparation of a good electrical conductivity and high mechanical properties of MWNTs/PVDF composite material is particularly important.(2) The rotor structure is another important factor affecting the properties of MWNTs/PVDF composites. The simulation results show that the new type of chaotic rotor has stronger distributing and mixing ability than the standard rotor. The experimental results show that the MWNTs/PVDF composites prepared by the chaotic rotor have better conductivity and mechanical properties than the ordinary rotor.(3) The microstructural and macroscopic properties of MWNTs/PVDF composites were significantly affected by the tensile effect. For the MWNTs/PVDF composites with different loading values near the percolation threshold, the volume resistivity increases with increasing tensile strain. After stretching, the dielectric constant of the composites decreases and the volume resistivity increases.