Study On The Preparation Mechanism And Performance Of Carbon Nanotube/Polymer Conductive Composites Under The High Frequency Electric Field

Polymer-based carbon nanotubes(CNTs)composites possess the advantages of both conductivity,thermal conductivity and comprehensive mechanical properties of CNTs and polymer materials.However,CNTs are prone to agglomeration and tend to be randomly arranged in the matrix during the composite process,which makes the comprehensive properties of CNTs and polymer materials need to be improved.At present,the dispersion of CNTs can be improved by surface modification,ultrasonic dispersion and strong shear stress field,while the orientation distribution of CNTs in polymer matrix can be improved to some extent.However,the mixed dispersion of CNTs in polymer matrix is still very difficult,which directly restricts the popularization and application of polymer-based CNTs composites.Therefore,how to prepare CNTs composites with high performance and anisotropy is a difficult problem in the processing of polymer-based CNTs composites.In this paper,a self-developed high-frequency electric field and normal stress field synergistic plasticizing processing equipment is used to introduce the normal stress and highfrequency electric field into the processing of multi-walled carbon nanotubes(MWCNTs)/polymer composites synergistically.The MWCNTs in the matrix are aligned by the high-frequency electric field while the composites are melt-plasticized..The aligned MWCNTs/polymer composites with high conductivity and low percolation thresholds are obtained.In this paper,a physical mathematical model of rotational motion of CNTs in high viscous melt under high frequency electric field is established,and the influencing factors of MWCNTs induced by electric field in melt environment are analyzed.The evolution prediction curves of the relationship between the angle between the long axis of MWCNTs and the direction of electric field line versus the applied time of electric field under different conditions are obtained.MWCNTs/polymer composites were prepared by high frequency electric field and normal stress field synergistic plasticizing equipment under various processing parameters.The theoretical predicted results were validated by correlating the orientation of MWCNTs in the composites with the conductivity of the composites.The results show that,as for the influence factors such as the applied time of electric field,the matrix viscosity and the aspect ratio of MWCNTs,the experimental results are in good agreement with the theoretical calculation,but for the forming temperature and pressure,the control equations need to be further optimized.The properties of polypropylene(PP)/aligned MWCNTs composites synergistically processed by high frequency electric field and normal stress field were characterized comprehensively by transmission electron microscopy,Raman spectroscopy,electrical conductivity and dielectric properties testing,dynamic rheological test and thermogravimetric analysis.It is confirmed that MWCNTs exhibit obvious alignment and anisotropy induced by high frequency electric field,and significant improvement of the conductivity,dielectric properties and thermal stability as a result.This paper provides a new idea for the introduction of high-frequency electric fieldinduced orientation into the processing of polymer-based conductive composites,which has important theoretical and application value.