【作者】 胡洪亮；

【导师】 张国；

【作者基本信息】 吉林大学 ， 材料学， 2013， 博士

【摘要】 导电高分子复合材料一般分为结构型导电高分子材料和复合型导电高分子材料两大类。相比结构型导电高分子材料的难熔、难溶、不易成型、环境稳定性差等缺点，复合型导电高分子材料可以通过改变基体和填料的种类以及填料用量可以在较大范围内调节材料的电性能，因此，复合型导电高分子材料在填料、基体的选择、制备等方面更具有优势，且来源广泛，受到众多学者的广泛关注。聚合物基正温度系数(PTC)材料作为导电高分子复合材料中的一种智能高分子材料，由于其具有特殊的温度响应能力而在加热材料、过热或过流保护器等领域得以应用。但随着社会的进步及人们需求的不断提高，人们对材料的性能提出了更高的要求。渴望发现新的高效填料与制备工艺，从而进一步改善材料的综合性能。本文从提高复合材料电导率，改善其PTC性能的角度出发，以碳系填料，石墨烯(G)、石墨(GP)、炭黑(CB)、碳纤维(CF)为主要填料采用共溶剂法制备工艺、热压还原工艺、旋涂蒸发工艺、高速机械混磨工艺制备了碳基聚合物电导复合材料。系统的研究了不同的制备工艺对填料的分散性能及对复合材料电学性能的影响。同时，研究了填料的分布形态、不同的填料体系、CF的氧化处理与基体性质对复合材料的电导率和PTC性能影响，实现了不同填料及基体间的优势互补，为PTC材料的加工和改性提供了新的思路。本文主要研究内容和创新性成果如下：1.提出将共溶剂法制备工艺与热压还原工艺相结合，制备了还原氧化石墨烯(RGO)/聚偏氟乙烯(PVDF)导电复合材料。研究表明，在1：9的水(H2O)/二甲基甲酰胺(DMF)的混合溶剂中氧化石墨烯(GO)的浓度提高了2.98倍，且能够形成均一稳定的溶液。在RGO/PVDF复合材料的制备过程中，通过热压还原工艺消除了材料内部孔结构对复合材料后期电学性能的影响。研究发现，RGO/PVDF导电复合材料呈现NTC效应，且循环测试过程中室温电阻呈现下降趋势。对RGO/PVDF复合材料的结晶性能研究发现，RGO的加入促使PVDF发生了α相到β相的晶型转变。2.研究了CF、CB与RGO粒子的相互作用对RGO/PVDF导电复合材料的PTC性能影响。对复合材料的导电性能、PTC性能的研究表明，具有一定长径比的CF优于CB。通过对CF进行氧化处理，能够有效的消除材料的NTC效应，改善材料的循环稳定性。并通过X射线衍射(XRD)、透射电子显微镜(TEM)全面分析了RGO/PVDF、CF/RGO/PVDF、CB/RGO/PVDF不同复合体系的结晶性能及不同形态填料间的相互作用机理。3.提出采用旋涂蒸发工艺制备了具有分离结构的纳米石墨烯(GNS)/超高分子量聚乙烯(UHMWPE)导电复合材料，系统的研究了制备工艺对GNS/UHMWPE导电复合材料电学性能的影响。研究表明旋涂蒸发工艺制备的GNS/UHMWPE导电复合材料具有较低的逾渗阀值仅为0.028vol%。同时研究发现，采用溶液共混法制备的GNS/PVDF复合材料呈现NTC效应，采用旋涂蒸发工艺制备的分离结构GNS/PVDF复合材料呈现PTC效应。在分离结构GNS/PVDF导电复合材料中，通过控制GNS填料含量的变化，能够实现GNS/PVDF复合材料PTC转变温度的可控性。GNS/PVDF复合材料的XRD、DSC测试表明，分离结构复合材料中GNS的加入并未改变PVDF的结晶性能。4.本文使用高速机械混磨工艺制备了CB/UHMWPE分离结构导电复合材料，复合体系的逾渗阀值仅为0.4vol%，与传统熔融共混工艺和部分溶液共混工艺制备的同一体系导电复合材料相比，复合材料的逾渗阀值显著降低。同时，通过高速机械混磨工艺制备了CB/GP/UHMWPE、 CB/CF/UHMWPE、CB/UHMWPE/HDPE导电复合材料，并对其PTC性能进行了系统的研究。通过改变界面处填料形态及基体性质改善了复合材料的PTC性能，与CB/UHMWPE复合体系相比PTC强度分别提升了1.66倍、1.85倍，且当UHMWPE/HDPE为1:3时消除了NTC效应。随着热循环测试的进行，CB/UHMWPE复合材料的PTC强度提高了2.07倍，呈现上升趋势。通过控制复合材料热压工艺改变了CB/UHMWPE复合材料界面处的填料分布形态，实现了CB/UHMWPE导电复合材料的PTC强度的可调性。更多还原

【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.更多还原