【作者】 韩蕾蕾；

【导师】 谢长生； 蔡水洲；

【作者基本信息】 华中科技大学 ， 材料学， 2007， 硕士

【摘要】 将炭黑(carbon black CB)分散到聚合物基体中制得导电复合材料,当炭黑含量超过某一临界值(称为渗阈值)时,复合材料的电阻出现显著的下降。进入导电区的复合材料接触到有机溶剂或蒸汽时,由于吸附有机溶剂或蒸汽而使聚合物基体产生溶胀或溶解,导致复合材料内部的炭黑粒子渗阈通道被破坏,复合材料的电阻显著上升。基于这一特性,炭黑/聚合物复合材料可作为化学电阻器或电子鼻来检测、鉴别和定量分析不同的有机溶剂或蒸汽,并在许多领域获得应用。本文通过溶液共混成功制备出炭黑填充聚乙烯基体气敏导电复合材料,结合材料的微观分析(场发射扫描电镜),得到固化后的复合材料为多孔结构。实验采用丝网印刷制作的梳状电极和聚乙烯(polyethylene PE)作为基片材料,解决了电极一致性和复合材料的裂纹现象。实验证明,复合材料中填料的浓度显著影响其电阻值,它随炭黑含量的变化过程中出现最小值,当复合材料的电阻出现最小值后,炭黑含量的变化不会影响复合材料的电阻值,但是复合材料的最佳炭黑含量要高于渗阈值。实验进一步探讨了溶剂性质(浓度、极性、溶度参数)对复合材料气敏性能的影响。另外,对40次重复试验进行数据分析,引入标准偏差和相对误差值来评价元件的一致性。采用溶液共混法得到的CB/PE复合材料对二甲苯、氯仿等挥发性有机化合物有较好的气敏性、良好的稳定性和重复使用性。当CB/PE导电复合材料掺杂乙烯-醋酸乙烯酯共聚物(ethylene-vinyl acetate resin EVA)后,CB/PE-EVA复合材料对弱极性和极性(乙醇、甲醛)溶剂表现出一定的敏感性,但同时增加了CB/PE-EVA复合材料的“负蒸汽系数”效应。实验表明:溶液共混法制备的炭黑/聚乙烯气敏导电复合材料是一类性能优良、具有良好应用前景的气敏材料。更多还原

【Abstract】 Dispersion of carbon black (CB) into an insulating polymeric matrix yields conductive composite material characterized by a sharp decrease of its electrical resistivity when the filler content exceeds a critical value called percolation threshold. For the composites having sufficiently high conductivity, a significant increase in their electrical resistance can be seen when the composites are contacted with organic solvents or vapors. Swelling or dissolution of the polymer matrix and the resultant destruction of the conduction paths within the composites should take the responsibility. Based on this feature, the composites are capable of acting as chemiresistors or electronic noses to detect, distinguish and quantify various solvents or solvent vapors and might find applications in many fields.In the present thesis, we successfully fabricated Carbon Black/Polyethylene (PE) conductive polymer composites by solution blending. With materials’microstructure analyzing (Field Emission Scanning Electron Microscope), the composite material had porous structure after curing. The comb-shaped electrode was produced by screen printing, which had good consistent. We chose plastics as substrate material, in order to avoid cracks.The filler concentration in the composites notably influences the resistance of the composites. It can be seen that a minimum value resistance appears when the content of CB increases to a certain extent and the value of this optimum CB content is higher than the related percolation threshold.Properties of solvent that influence the composites gas sensibility are investigated, such as vapor concentration, polarity and solubility parameter. Referring to the values of standard deviation and relative error as the evaluating parameters, the consistency of gas sensing components was analyzed via 40 times repetitious experimental data. All the composites prepared in this thesis show a good sensibility to Volatile Organic Compounds having some solvency ability to matrix and also have a good stability and reuse ability, such as xylene and chloroform. When adulterating CB/PE with EVA (ethylene-vinyl acetate resin), the CB / PE-EVA was sensitive to weak polarity and polarity organic solvents (ethanol, formaldehyde) but had more“NVC”(Negative Vapor Coefficient) phenomenon.All of the experimental results indicate that the PE/CB composites prepared by polymerization filling exhibit good gas sensing properties, demonstrating the promising application potential.更多还原