The Study Of Electrical Properties And Responsive Behaviors In Different External Fields Of Segregated CB/PP/UHMWPE Conductive Polymer Composites

The development and application of conductive polymer composites (CPCs) is an important issue for the functionalization of modern polymer materials. CPCs are conductive polymer composites which are obtained by adding one or more kinds of conductive fillers into polymer matrix and composited through physical or chemical methods. CPCs have been widely used as antistatic materials, self-regulated heaters, electromagnetic shielding, sensors and detection systems, etc. The percolation phenomenon is an important phenomenon of CPCs. The percolation thresholds of CPCs fabricated by traditional methods are always high. However, the high content of conductive fillers always leads to inferior mechanical properties and processing fluidity.In this thesis, carbon black (CB), Polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMWPE) were blended by using ethanol assisted ultrasonic dispersion-hot compression method. CB particles were then selectively distributed on the interface between PP and UHMWPE matrice through this process. Consequently, segregated CB/PP/UHMWPE CPCs were obtained and the percolation threshold of CB filled CPCs was reduced significantly. The structure and morphology of the conductive composites were analyzed by optical microscope observation and scanning electron microscope. Besides,the effect of CB with different structure on the percolation behaviors of the composites was studied. It is found that CB particles are segregated by UHMWPE in the segregated conductive composites, and CB with high structure is mainly distributed at the interface of PP and UHMWPE while CB with low structure is distributed at the interface of PP and UHMWPE and PP matrix. In addition, the percolation threshold of the segregated conductive composite fabricated by CB with high structure is lower.In recent years, CPCs have aroused great attention due to their sensitive characters under field stimulation. In this thesis, samples with filler content just little beyond the percolation threshold of CB/PP/UHMWPE CPCs were employed to investigate the responsive behavior and sensing mechanisms under temperature and stress. In the temperature-resistivity behavior test, the variation of temperature-resistivity behaviors during the mutiple heating-cooling cycles and after long term isothermal heat treatment were studied. The morphology evolution of CPCs during the heating process of one cycle was observed by optical microscope and the relationship of morphology evolution and temperature-resistivity behaviors were analyzed. In the strain sensing behavior test, Stress-Strain behavior of CPCs under different tensile speeds was studied. Compare the coupling research of the mechanical and electrical properties under cyclic tension were studied. Also, the evolution mechanisms of e temperature-resistivity behaviors and strain sensing behaviors under fields above were analyzed.