Preparation And Properties Of High Performance Poly(Ether Ether Ketone)-based Conductive Composites And Films

Poly（ether ether ketone）（PEEK）, which is a kind of special engineering plastics with excellent comprehensive performances, has an important strategic significance and receives a lot of attention in many countries. PEEK has broadened the application scope from aerospace and military to civilian market after many years of development.In order to meet the requirements of various areas, the studies on PEEK blends and PEEK-based composites have become a hot point at home and abroad. To obtain PEEK conductive composites and films with excellent properties, in this thesis, the matrix, the conductive filler and relative modification methods were discussed through a series of experiment; and then, from the point of processing additive, the formula of high performance PEEK conductive composites was determined and a series of PEEK conductive films were prepared based on this formula, and their comprehensive properties were investigated in detail.The matrix resin are highly required to prepare high performance PEEK-based conductive composite films, which is because even and smooth films need be obtained by using PEEK with low melt index as the matrix resin. Therefore, PEEK with the melt index of 15g/10 min and 25g/10 min were selected for optimization of the resin matrix. These two kind of PEEK both have a lower melt index（higher melt viscosity） and lower molding shrinkage than the PEEK matrix with a higher melt index（lower melt viscosity）, which is good for the film manufacturing. However, in the course of preparing the MWCNT/PEEK composites, the dispersion of the conductive fillers in the matrix with lower melt index（15g/10min） was worse than the PEEK matrix with higher melt index（25g/10min） and the agglomeration of MWCNTs in the matrix of 15g/10 min was more serious. Therefore, the PEEK matrix of 25g/10 min melt index was chosen. Then three kinds of carbon conductive filler:carbon fiber（CF）, carbon black（CB）, and multi-walled carbon nanotubes（MWCNTs）were selected to prepare the PEEK-based composites at the same condition. By the evaluation of the conductivity, mechanical property and thermo-stability of these three kinds of composites, it was found that the performance of MWCNTs/PEEK composite was better than that of CF/PEEK and CB/PEEK composites. The properties ofconductive composites depend not only on the matrix and fillers, but also on the conductive network and effective connectivity of conductive fillers formed in the matrix, so MWCNTs was optimized as the ideal conductive filler for PEEK. After this,polyether imide（PEI） and polyether sulfone（PES） were used as the modification agents of PEEK, respectively. Moreover, the results showed that this modification was benefit to the dispersion of MWCNTs in the PEEK matrix, but negative to the effective connectivity of MWCNTs in the matrix; while the MWCNTs without modification was benefits to the effective connectivity but negative to the dispersion of MWCNTs in the PEEK matrix. This phenomenon result from that the surface modification solves the agglomeration of MWCNTs to some extent but the insulating substance around MWCNTs will also affect the effective connectivity of MWCNTs.The comprehensive properties of the MWCNTs/PEEK composites with pristine MWCNTs were better than that with modified MWCNTs. In order to further improve the dispersion of MWCNTs in the PEEK matrix, high temperature lubricant（GPPS）and polyaryletherketone liquid crystal（FPEDEKKLCP） were chosen as the processing additive and investigated systematically for MWCNTs/PEEK with constant MWCNTs contents but different GPPS or FPEDEKKLCP contents, it was found that GPPS and FPEKEKKLCP were both benefit to the properties of the MWCNTs/PEEK composites. Specially, when the content of GPPS is 1 wt% or the content of FPEDEKKLCP is 0.4 wt%, the properties of composites were the best of each system. Thereby, the matrix resin, conductive fillers, the method of modification and the processing additives of the composites were optimized to prepare the composite films.Based on the result above, two series of PEEK-based conductive composite film were prepared with the processing additive of GPPS（1 wt%） and FPEDEKKLCP（0.4wt%）, respectively. The conductivity of composite film can reach 1.0 Sm^-1 by tuning the content of MWCNTs. Considering the excellent strength and thermo-stability, the MWCNTs/PEEK composite films will be more promising in the fields of electromagnetic shielding in harsh environment.