【作者】 刘华斌；

【导师】 肖汉宁；

【作者基本信息】 湖南大学 ， 材料学， 2012， 博士

【摘要】 在传统材料中添加纳米粉体可极大改善其相关性能，但纳米氧化物粉体因表面能大极易团聚，表面具有较强的亲水性而难与聚合物基体粘结相容等问题限制其在诸多工业领域的广泛应用。对纳米氧化物进行表面改性是解决这类问题的有效手段，通常有两种思路：一是在制备纳米粒子的过程中对工艺进行调整和控制，二是在获得纳米粒子后对其进行表面改性处理；前者能够降低纳米粒子的硬团聚趋势，但涉及工艺复杂、影响因素多，且在纳米粒子应用之前还存在继发团聚；而后者是在纳米粒子的应用阶段进行改性处理，主要解决纳米粒子的软团聚，更利于发挥纳米粒子的优异性能。本文通过对纳米氧化物的颗粒表面进行湿法改性，研究了不同类型改性剂在纳米氧化物表面的吸附行为，揭示了其在水性介质中的分散稳定机理，并将有机化改性的纳米颗粒添加到聚丙烯树脂中，制备了纳米复合材料，分析了改性纳米粒子填料对复合材料力学等性能的影响。具体的研究内容和结果包括以下几个部分：（1）研究了不同类型表面活性剂（TPB、CTAB、SDS和PEO）单独或共同在纳米氧化物表面的吸附行为。FTIR结果表明离子型表面活性剂TPB、CTAB与SDS在纳米氧化物表面的吸附机理主要为静电力作用；非离子型聚合物PEO在纳米氧化物表面的吸附机理主要为氢键作用；离子型表面活性剂/非离子型聚合的二元混合体系（CTAB/PEO及SDS/PEO）在纳米氧化物表面产生共同吸附，同时存在一定的竞争关系。吸附实验表明离子型表面活性剂的吸附量与本身浓度、pH值、电解质离子强度和类型等因素有关，非离子型聚合物在纳米氧化物表面的吸附量与自身分子量大小与吸附构象有关。（2）纳米氧化物吸附表面活性剂后，颗粒表面的电荷密度、ζ电位和双电层结构将发生变化。吸附阴离子型或阳离子型表面活性剂后，纳米氧化物颗粒等电点分别向低或高pH值方向移动，位移量与表面活性剂浓度或聚合物的平均相对相对分子量相关。而吸附非离子型聚合物后，纳米氧化物ζ电位的绝对值虽然会减小，但等电点位置几乎不变。在水性介质中离子型表面活性剂主要通过静电斥力作用分散纳米氧化物，而非离子型聚合物主要通过空间位阻作用分散纳米氧化物，在离子型表面活性剂/非离子型聚合的二元混合体系中，二者协同配合通过静电位阻作用分散纳米氧化物。（3）用硅烷偶联剂A151在醇水介质中对纳米ZrO₂进行了表面改性，并以其作填料制备了PP/ZrO₂纳米复合材料。FTIR结果表明A151与ZrO₂发生了化学接枝反应；接触角测量结果表明，A151有效改善了纳米ZrO₂粒子表面的润湿性能，由亲水性表面变成疏水性表面，增强了其与聚合物基体的界面相容性和结合强度。添加改性纳米ZrO₂提高了复合材料的拉伸强度和断裂伸长率，并增大了复合材料的冲击强度和模量；提高了复合材料的结晶温度，在PP基体中分散均匀的纳米ZrO₂既可充当刚性支撑点，又可以阻止硬质粒子的嵌入和磨削，提高复合材料的耐磨性能性能。（4）研究了有机季铵盐OTAC在水性介质中对纳米蒙脱土的插层改性，并以制得的OMMT为填料制备了PP/OMMT纳米复合材料。XRD和FTIR结果表明OTAC分子链进入到了蒙脱土片层结构的层间，插层改性后蒙脱土片层间距由1.51nm最大增大至3.80nm；SEM观察结果显示蒙脱土由改性前的紧密堆积结构变成改性后的鱼鳞态片状结构；接触角测量和沉降实验结果表明，有机化改性改善了蒙脱土颗粒的亲油性，在制备聚合物基复合材料时提高了其与聚合物分子之间的相容性；当OMMT添加量为3⁴wt%时，可有效提高复合材料的拉伸强度和冲击强度；DSC测量结果表明添加OMMT的复合材料的热降解温度滞后约有25oC，提高了材料的热稳定性。更多还原

【Abstract】 The performance of conventional composites have been proved to be improved greatlyafter addition of nano-materials into their formulations, while the tendency of aggregation ofoxide nanoparticles due to large surface energy and poor interface compatibility between thehydrophilic filler surface and hydrophobic polymer matrix confine the industrial applicationof oxide nanoparticles. The effective solution is deployment of surface modification on oxidenanoparticles. This approach normally involves two aspects. One is procedure regulation ofnanoparticles during their synthesis process; the other is conduction of surface modificationon the existing oxide naoparticles. For the former approach, there are many technical processconcerns and complex factors, and it is difficult to prevent the re-aggregation. For the later,the modification is carried out in case oxide particles are applied, which favors highlighting ofthe advantages of nanoparticles. In this work, wet modification is adopted for altering surfacefeature of oxide nanoparticles. Adsorption behaviors of various surfactants on oxide surfacewere investigated in details, and the mechanism on stabilization of aqueous dispersions wasalso discussed. Moreover, PP matrix composites were prepared by addition of modified oxidenanoparticles. Systematic experimental study was carried out to reveal the influences ofmodified nanoparticles on the mechanical performance of the composites.Belows are the main work scopes and the relevant results in the dissertation.（1） Individual and simultaneous adsorption behaviors of various surfactants （TPB, CTAB,SDS and PEO） on surface of oxide nanoparticles were studied. FTIR results indicated that theadsorption of ionic surfactants CTAB, TPB and SDS on oxide surface originated from theelectrostatic interaction, while adsorption of non-ionic polymer PEO depends on hydrogeninteraction. Simultaneous adsorption occurred on the oxide surface in the binary mixturessystem （CTAB/PEO and SDS/PEO）, and the competitive behavior was also observed.Experimental study on adsorption isotherm demonstrated that the absorbed amount of ionicsurfactants greatly depends on the concentration, pH value, electrolyte ionic concentration andit’s type. While the absorption amount of non-ionic polymer is closely related to the molecularweight and their configuration on oxide surface.（2） Charge density, zeta potential and double layer structure of oxide particles showeddifferent properties after surface modification. The pHiepof oxide particles moved towards tolower or higher pH value after adsorption of ionic or cationic surfactants, respectively. The shift extent depends on the surfactant concentration and the polymer molecular weight. Theabsolute value of the zeta potential of oxide particles would reduce after the adsorption ofnon-ionic polymer, while, the pHiepremains constant.The repulsion interaction of oxide particles modified by ionic surfactant comes from theimprovement of static interaction in aqueous solution. Non-ionic polymer offers stericrepulsion for dispersion of oxide nanoparticels. The electrostatic repulsion can be realized inbinary mixtures solution of ionic surfactant and non-ionic polymer to provide improvement ofdispersion of oxide nanoparticles.（3） Surface of ZrO₂particles was modified by silane coupling agent （A151） inalcohol-water solvent and used as filler in PP/ZrO₂nanocomposites. Chemical reaction wasfound between A151and ZrO₂from the FTIR analysis results. The wettability of ZrO₂nanoparticles has been promoted effectively upon the modification of A151. Surface of theoxide was changed to hydrophobic from hydrophilic, which enhances the interfacecompatibility with polymer matrix. Experimental results on mechanical performanceindicated that the addition of the modified nano-ZrO₂particles improves the tensile strengthand the elongation performance, as well as the impact strength and module of the composites.It should be noted that the improvement of mechanical performance was confined by thedispersion of nano-ZrO₂.（4） Intercalation modification of montmorillonite by OTAC was studied to improvePP/OMMT composites performance. XRD and FTIR results presented that the lamellarstructure of the layered OMMT was intercalated by OTAC. The layer spacing was extendedfrom1.51nm in Na-MMT to3.80nm by intercalation with alkyl chains. The SEM analysisrevealed that the morphologies change from sopherical-like particles to high-aspect ratioflakes after modification. The hydrophilic surface of Na-MMT was tranfered to hydrophobicafter modification, which greatly benefits the interface compatibility between the filler and PP.In case of addition of OMMT with3⁴wt%, the tensile and impact performance wereimproved obviously. Besides, the thermal degradation temperature of the nanocompositeslowers25oC in the DSC curve, revealing the improvement of the thermal stability of thePP/OMMT composites.更多还原