The Research On PTC Effect Of Polymer Conductive Composites Based On PVDF

PTC(Positive Temperature Coefficient)material is positive temperature coefficientmaterial, Its characteristics is the resistivity increases with increasing temperature.Depending on the substrate material, currently, the PTC material is divided into twotypes of ceramic matrix and polymer matrix. Polymer-based PTC materials is acomposite material based on organic polymer matrix, with the inorganic conductive filler.Polymer-based PTC material integrated conductivity of the inorganic filler and thefunction about flexibility and machining performance of polymer materials. So thematerial has very good performance: the lower room temperature resistivity and highPTC intensity,low cost,ease of processing molding,etc. Polyvinylidene fluoride is anexcellent thermal stability of fluorine plastic,and ease of molding process,also has goodflexibility.Thus this paper select a polyvinylidene fluoride as a substrate material, studiedthe PTC Composites materials which use carbon nanotubes, graphene, carbon black asconductive filler, including preparation, PTC performance, flexibility, thermal stability.Produced the PTC intensity to reach the5flexible PTC material of low resistivityThis paper will focus on important indicators including the conductivity, PTC effect,flexibility, thermal stability of the composites, testing with different conductive filler andPVDF matrix,by means of comparative experiments, macro-microstructure examination,the PVDF-based polymer matrix composite PTC performance are studied.First, studied the carbon nanotube/polyvinylidene fluoride composites. Found out thatthe electrical conductivity of multi-walled carbon nanotube nanocomposites increaseswith increasing nanotube content. Made different content of carbon nanotube composites,When carbon nanotube content of2.5wtï¼…, the conductivity of composite materials is0.10the PTC intensity is4.0, and has good flexibility and thermal stability. Tofurther improve the performance of the MWCNT/PVDF nanocomposite membranes,regulative the morphology of its modified. Select the silane coupling agent KH570 modified material. The result shows that when KH570content is appropriate, theconductivity of the material significantly improved. At the same time, the right amount ofKH570modification can improve the PTC intensity of the material, and the flexibilityand thermal stability of the materials also have some improvements.The same as the the carbon materials of graphene materials is not only the thinnestknown material, but also very strong and hard. As a single mass, the electron transferrate at room temperature is faster than the all known conductor.Therefore, writer choosengraphene as a conductive filler composite to study PTC properties. Research GNS/PVDF nanocomposite membrane PTC performance, flexibility, thermal stability. WhenGNS mass fraction of up to5.0wt%, the conductivity of the material at room temperatureis0.384, the PTC intensity is3.5, and has good flexibility, but poor thermalstability.In order to further improve the composite PTC effect, to mix CB and MWCNTtogether by a certain percentage with PVDF. Obtained with low resistivity and highflexible composites, with improved PTC intensity. When the CB and MWCNTconcentration of3wt%and1wt%, the PTC intensity of composite materials to reach5.0.In this composite system,when the MWCNT and CB filled polymer matrix,they interact to produce synergistic effects,MWCNT and CB in the polymer matrix to form a string structure.Adding a small amount of MWCNT in the CB conductive filler,CB provide short-range conductivity,MWCNT provide remote conductive.This will be favored to the formation of the conductive system,thus to enhance the conductivity of the polymer matrix.While the long-range conductive network formed by the destruction of MWCNT,requires a large volume expansion.To a certain degree has improve the PTC intensity of composite materials.