【作者】 张莹莹；

【导师】 赵东林；

【作者基本信息】 北京化工大学 ， 材料学， 2008， 硕士

【摘要】 填充型导电复合高分子材料作为气体敏感材料由于具有质量轻,成本较低,易于加工成型,宜于大规模生产等特性而受到广泛重视。与其他的导电填充粒子相比,碳纳米管因尺寸小、比表面积大、呈中空结构而具有良好的吸附能力,然而碳纳米管易缠结和团聚,它在高分子基体中的分散度成为影响碳纳米管/聚合物复合高分子材料导电和气敏性能的关键。基于上述考虑,本研究以碳纳米管为导电填充粒子,聚甲基丙烯酸甲酯(PMMA)和聚醋酸乙烯酯(PVAc)为基体,通过超声分散和原位聚合的方法,制备出了性能优良的复合膜,并对其导电气敏性能进行了详细的研究。主要工作如下：1.以甲基丙烯酸甲酯(MMA)为单体,偶氮二异丁腈(AIBN)为引发剂,采用原位聚合法制备了碳纳米管/PMMA复合材料,通过聚合物的分子量来考察复合材料的聚合情况,以及碳纳米管含量对原位聚合反应的影响，并进一步研究所制得的复合膜微观结构。通过研究碳纳米管含量对碳纳米管/PMMA复合膜导电性能的影响,发现随着碳纳米管含量的增加,复合膜电阻率逐渐降低,在聚合过程中通入氮气的条件下所制得的复合膜较未通入氮气制得的复合膜导电性能要好。而在一定浓度四氢呋喃、丙酮、乙醇气氛中,研究了碳纳米管含量对CNT/PMMA复合膜的气敏性能的影响,同时发现复合膜对三种气氛的气敏响应都是随着时间的增加先增大后减小,在同一浓度四氢呋喃、丙酮、乙醇气氛中,复合膜气敏性能大小关系如下：四氢呋喃>丙酮>乙醇；复合膜的响应时间顺序为：丙酮>四氢呋喃>乙醇。2.研究通过将碳纳米管/PMMA复合材料加入PVAc,制备的碳纳米管/PMMA/PVAc复合膜的微观结构以及其导电性能,发现随着碳纳米管含量的增加,复合膜电阻率逐渐降低,复合膜的渗流阈值为3wt%。在一定浓度四氢呋喃、丙酮、乙醇气氛中,碳纳米管/PMMA/PVAc复合膜的响应随着时间的增加先增大后减小,在同一浓度的四氢呋喃、丙酮、乙醇气氛中气敏性能的大小为：四氢呋喃>丙酮>乙醇。3.在不同浓度的四氢呋喃、乙酸乙酯、甲苯、二甲苯气氛中,CNTs/PMMA/PVAc复合膜电阻变化峰形相似,呈单峰形状,在吸附区,随着时间的增加,复合膜电阻增大；在解吸区,随着时间的增加,复合膜电阻逐渐减小。同时可以看到,每种气氛中,随着蒸气浓度的增大,复合膜电阻逐渐增大。其中,在浓度为0.8-5.6ppt四氢呋喃气氛中,浓度为0.6-5.4ppt乙酸乙酯气氛中,浓度为0.6-6ppt甲苯气氛中,浓度为0.5-8ppt二甲苯气氛中,CNTs/PMMA/PVAc复合膜的气敏响应敏感率都随着每种蒸气气氛浓度的增加近似呈线性关系增加。复合膜在乙酸乙酯气氛中的电阻响应变化最大,四氢呋喃其次,在二甲苯中的电阻变化最小,而且复合膜在甲苯和二甲苯中气敏响应与气氛浓度所呈的线性关系也较差。在四氢呋喃、乙酸乙酯、甲苯、二甲苯四种气氛中,随着CNTs/PMMA/PVAc复合膜基体中PVAc含量的增加,气敏响应也逐渐降低。CNTs/PMMA/PVAc复合膜在四种气氛中的气敏性能大小为：乙酸乙酯>四氢呋喃>甲苯>二甲苯。(4)通过原位聚合法制备的碳纳米管/PVAc复合膜以及碳纳米管/PVAc/PMMA复合膜导电性能较差,吸波性能较弱。更多还原

【Abstract】 As a gas sesintive material, the loading electric conduction polymer composite materials are received wide interest, because they have light weight, low cost, and are easy to shape and suitable for production on a large scale, etc. Compared with other electric conductive filler, carbon nanotubes(CNT) have remarkable absorption ability due to its distinguished properties such as small diamater, high aspect ratio and hollow tube structure. However, it is generally easy to aggregate and tangle. The dispersion of CNT in polymeric matrices considerably affects conductivity and gas sensitivity of CNT/polymer composite. Based on the above consideration, thin films of poly(methyl methacrylate)(PMMA), poly(vinyl acetate)(PVAc) and CNT in this research were produced by ultrasonic dispersion and in-situ polymerization, CNT as conductive filler and PMMA and PVAc as polymeric matrices. Furthermore, conductivity and gas sensitivity of the film were studied in detail. The research work consists of:1. CNT/PMMA composites were fabricated by in situ polymerization, with the initiator2,2’-azobisisobutyronitrile (AIBN), the matrix methyl methacrelate (MMA). The polymerization of CNT/PMMA composites was reviewed by the molecular weight of polymer. CNT concentration dependences of the reaction of CNT/PMMA composites and the microstructure of the film fabricated by CNT/PMMA composites were also investigated. Carbon nanotubes concentration dependeces of the electric resisitance of the carbon nanotubes/PMMA composite film was studied. The volume electric resistivity of carbon nanotubes/PMMA decreased with increasing the content of carbon nanotubes. The film conductivity is better during the polymerization in a nitrogen than in no nitrogen. At a fixed vapor of tetrahydofuran (THF), acetone, ethanol, CNT concentration dependences of the electric resistance response of the CNT/PMMA composite film was investigated. The maximum electric resistance response of the film to the above three kinds of vapor increased and then decreased with increasing time. At the same concertration of THF, acetone, ethanol, the electric resistance response of CNT/PMMA composite film is as follows:THF>acetone>ehanol; the order of the response time of CNT/PMMA composite film is as follows: acetone> THF>ehanol.2. CNTs/PMMA/PVAc composite film was fabricated through PVAc blends with CNT/PMMA. The microstrcture and its electrid properties were investigated, the volume electric resistivity of CNTs/PMMA/PVAc composite film decreased with increasing the content of carbon nanotubes. The electrical percolation thresholds were at3wt%. At a fixed vapor of tetrahydofuran (THF), acetone, ethanol, the maximum electric resistance response of the film to the above three kinds of vapor increased and then decreased with increasing time. At the same concertration of THF, acetone, ethanol, the electric resistance response of CNTs/PMMA/PVAc composite film is as follows:THF>acetone>ehanol.3. At different vapor concentration of THF, ethyl acetate, toluene, xylene, the resisitance change of CNTs/PMMA/PVAc composite film all presents single apex. In the adsorption zones, the electric resistance increased with increasing time. And in the desorption zones, the electric resistance decreased with increasing time. The electric resistance of the composite film began to increase with the vapor concentration increasing to the above four kinds of vapor. In THF vapor at a concentration of0.8-5.6ppt, the electric resistance of the composite film is linear increasing with THF concertration increasing. It represents the resemblance in ethyl acetate vapor at a concentration of0.6-5.4ppt, in toluene vapor at a concentration of0.6-6ppt, in xylene vapor at a concentration of0.5-8ppt. The change of electric resistance response in ethyl acetate vapor is the biggest, and then in THF vapor. It is the smallest in xylene vapor. The linearity in toluene and xylene vapor are inferior. In THF, ethyl acetate, toluene, xylene vapor, the the electric resistance response of CNTs/PMMA/PVAc composite film decreased with increasing the content PVAc. The electric resistance response of CNTs/PMMA/PVAc composite film to above four kinds of vapor is as follows:ethyl acetate>THF> toluene> xylene.4. The CNTs/PVAc composite film was fabricated by in-situ polymerization. Conductivity of the CNTs/PVAc and CNTs/PVAc/PMMA composite film were all not remarkbale, and wave adsorption ability was feebleness.更多还原