原位化学氧化接枝聚苯胺包覆粉煤灰漂珠及其电流变特性研究

Polyaniline(PAn) has been growing concern as electrorheological fluid(ERF) due to its density, conductivity controllability, stability to environment and little of corrosion to apparatus. However, it is still limited to be applied because of strong aggregation leading to bad dispersity and high current density. Usually it can be composited, doped and coated with inorganic matters to improve the electrorheological properties. Float fly ash bead(FFAB) is one of fly ash which has the lowest density and has been applied in building material industry widely for its excellent heat resistance and high strength, but it is novel to be used as ERF. Firstly, FFAB is separated by flotation method in this subject, then 3-aminopropyl triethoxysilane(APTES) is introduced to couple with FFAB and then,FFAB-APTES is obtained. After that, aniline polymerize on the surface of FFAB-APTES,then the FFAB-APTES/PAn composites with core/shell structure are synthesized by in situ chemical oxidative grafting polymerization. The chemical structure, heat stability and dielectric property of the composites are characterized. Next, the rheological property, sedimentation and mechanical property of the ERF with FFAB-APTES/PAn as dispersed phase and dimethicone as basic liquid are evaluated by apparent viscosity, sedimentation ratio and shear stress, respectively. The law and mechanism of ER effect on PAn induced by FFAB are discussed. The relationship between the composite content and the ER effect are also described.

聚苯胺由于密度、导电控制、环境稳定性和对电流变设备无腐蚀等特点已成为电流变液的主要研究对象，但是，聚苯胺聚集性强导致分散性差以及电流密度高，应用受限，通常将其与无机材料复合、掺杂、包覆以改善其电流变效果。粉煤灰漂珠是粉煤灰中密度最小的一种，且其热阻大、强度高等特性，在建材行业得到了广泛的应用，但作为电流变材料使用未见报道。本课题首先采用浮选法分离漂珠，再以3-氨丙基三乙氧基硅烷为偶联剂对其表面进行修饰，通过原位化学氧化法使苯胺在漂珠表面发生聚合，获得核/壳结构聚苯胺包覆粉煤灰漂珠复合材料，对其化学结构、热稳定性、介电性能进行测试；以二甲基硅油为基础液，复合材料为分散相，分析不同浓度下电流变液的表观粘度、剪切应力以及沉降率的变化规律，对电流变特性相关的流变性能、力学性能、沉降性能进行评价，阐明漂珠对聚苯胺电流变特性的影响规律及作用机理，建立分散相浓度与电流变特性之间的响应关系。

聚苯胺（PAn）的密度小、导电控制性强、环境稳定性好和对电流变设备无腐蚀等特点已成为电流变液的主要研究对象，但是，聚苯胺聚集性强导致分散性差以及电导率高易导致介电击穿，通常将其与无机材料复合以改善其电流变性能。粉煤灰漂珠(FAFB)是粉煤灰中密度最小的一种，因其热阻大在建材行业得到了广泛的应用。本项目以市售漂珠为原料，利用表面活性剂改性漂珠，再通过化学法制备了聚苯胺包覆漂珠，以此为分散相，二甲基硅油为基础液，分析了导电、介电及电流变性能以及沉降率的变化规律，该项研究为解决电/磁流变液悬浮性差和探讨多相体系下复杂电流变响应机制提供了实验依据，具有显著的科学研究价值。研究结果表明：.（1）表面活性剂修饰改性粉煤灰漂珠制备聚苯胺基复合材料的导电与介电性能.当CTAB浓度为0.20 mol/L，反应温度为80℃，反应时间为90min 时，改性效果最好；分解温度滞后了25℃；随链长增加FAFB-CnTAB/PAn的介电常数越大。此外，对比了非离子型聚乙二醇（PEG）和阴离子型表面活性剂十二烷基苯磺酸钠（SDBS）对漂珠进行改性，利用乳液聚合法合成了FAFB-PEG/PAn和FAFB-SDBS/PAn。电导率测试结果表明，引入FAFB后电导率显著降低；无论采用哪种表面活性剂修饰FAFB，复合材料的介电常数和介电损耗均随着FAFB掺入量的增加而减小。.（2）多相包覆粉煤灰漂珠的电流变性能.制备了m-FAFB/PAn、m-FAFB/PAn/ BaTiO3 和m-FAFB/BaTiO3/ PAn核/壳型复合材料，为此为分散相配制电流变液，结果表明m-FAFB/PAn较PAn及FAFB悬浮稳定性有所提高，电场对m-FAFB/PAn的电流变性能影响明显，但在外场为3.5kV/mm时发生介电击穿。以FAFB/PAn为基体，采用溶胶-凝胶-水热法制备了多层核/壳结构FAFB/PAn/BaTiO3复合材料。结果表明：FAFB/PAn/BaTiO3悬浮稳定性较FAFB/PAn差；外场为4.0kV/mm下剪切应力达631Pa。利用原位聚合法制备了PAn包覆FAFB/BaTiO3复合材料(FAFB/BaTiO3/PAn)，结果表明：FAFB/BaTiO3/PAn静置7d的悬浮率高达80%；外场为3.0kV/mm时剪切应力达到688 Pa，但其抗击穿能力较差，在3.5kV/mm时发生介电击穿。