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Study on the Preparation and PTC Behavior of Carbon-based Doped Polymer Composites

Author: HuHongLiang
Tutor: ZhangGuo
School: Jilin University
Course: Materials Science
Keywords: Preparation process Segregated structure Carbon-based filler Electricalconductivity PTC NTC
CLC: TB332
Type: PhD thesis
Year: 2013
Downloads: 128
Quote: 0
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Abstract


Conductive polymer composites are included structural conductive polymermaterials and composite conductive polymer material. Composite conductive polymermaterials can change the type of matrix and filler and filler content can be adjusted ina wide range of electrical properties of materials.So the composite conductivepolymer materials was concerned by scholar.Positive temperature coefficient (PTC)effect of polymer-based conductive composites is the non-linear response totemperature change of its resistivity,when temperature rising to the vicinity of themelting point of polymer matrix.This smart switch behaviour give it importantapplications in the field of heating materials,overheating or overcurrent protectiondevices and temperature sensors etc.But with social progress people put forwardhigher requirements for material.People want to find efficient packing and preparationprocess improving the performance of materials.In this paper we from the viewpoint of improve the conductivity and PTCperformance.We prepared carbon-based conductive polymer composites by co-solventmethod, hot pressing reduced method,spin coating evaporation method, high-speedmechanical mixing method.Study on the filler dispersion properties and electricalproperties of composite materials of the different preparation methods.At the sametime the distribution patterns of the single filler and double filler system and carbonfiber (CF) oxidation treatment and the mechanism of interaction of different fillerswas studied. We also study the electrical properties and PTC behavior of composites.The main contents and innovations are as follows:1. In this paper thermally reduced graphene oxide (RGO) polyvinylidene fluoride(PVDF) conductive composites was prepared by co-solvent method and spin coatingevaporation method.It was shown that in the1:9mixed solvent of H2O/DMF canimprove GO concentration which increased2.98times and can form a homogeneous stable solution. Eliminate the pore structure effect on electrical properties of thecomposite materials by hot pressing reduced method. The RGO/PVDF compositesshow an unusual resistance temperature behavior.The resistance decreases withtemperature,indicating an NTC behavior and the room-temperature resistivitydownward trend during the thermal cycles.we also found that RGO can promote αphase to β phase transformation of RGO/PVDF composite materials2. We found that the carbon fiber and carbon black (CB) can improve PTC behaviorof RGO/PVDF composites. However carbon fiber better than the CB in improve thePTC performance of RGO/PVDF composites. CF oxidation treatment can effectivelyeliminate the NTC effect and improving the cycles stability of composites. RGO/PVDF, RGO/CF/PVDF, RGO/CB/PVDF crystallization properties and mechanism ofinteraction between the filler was analyzed by XRD and DSC.3. The GNS/UHMWPE conductive composites was prepared by spin coatingevaporation process.Study has shown that the affect of preparation process forGNS/UHMWPE conductive electrical properties of composite materials. It wasshown that the percolation threshold is about0.028vol.%of GNS/UHMWPEconductive composites. We systematic study of the different structural forms effect onPTC of GNS/PVDF composites.It was shown that the GNS/PVDF composite exhibitsNTC by solution blending. In contrast the segregated structure of GNS/PVDFcomposite exhibits positive temperature coefficient by spin coating evaporationmethod.At the same time we found that PTC transition temperature move to the lowtemperature zone due to content decreased of fillers. GNS did not change thecrystalline properties of PVDF4. A simple high-speed mechanical mixing function was introduced to mix the fillerand matrix raw material. The percolation threshold of CB/UHMWPE was0.4vol%,which was much lower than those prepared by traditional melt blending and somesolution methods.In this paper CB/UHMWPE, CB/GP/UHMWPE, CB/CF/UHMWPE,CB/UHMWPE/HDPE was prepared by high-speed mechanical mixing method.Wefound that the morphological changes of the filler of composites lead to the PTCintensity increased1.66times,1.85times.We also found that UHMWPE/HDPE is1:3 eliminate the NTC effect.Thermal cycle test results showed that the CB/UHMWPEPTC intensity increased2.07times. We obtain a tunable PTC of resistivity in anelectrically conducting CB/UHMWPE composite by controlling the hot-pressingprocess.

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CLC: > Industrial Technology > General industrial technology > Materials science and engineering > Composite materials > Non-metallic composite materials
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