【作者】 贾清秀；

【导师】 张立群；

【作者基本信息】 北京化工大学 ， 材料加工工程， 2007， 博士

【摘要】 “粘土晶层悬浮液／橡胶乳液互穿纳米复合技术”(简称乳液共混法)是张立群教授等提出的一种简便高效的纳米复合技术，也是制备层状硅酸盐／橡胶纳米复合材料的重要方法之一。本论文主要是基于乳液共混法制备了粘土／橡胶纳米复合材料(橡胶基体主要包括丁苯橡胶、天然橡胶，粘土主要采用蒙脱土)，通过应用各种改性剂对复合材料的界面进行修饰，以改善粘土在橡胶基体中的分散和界面结合，从而提高复合材料的力学性能。此外，也考察了粘土与炭黑并用对复合材料结构性能的影响。本论文中主要采用两种方法对粘土／丁苯橡胶纳米复合材料进行有机改性和界面修饰。第一种为熔体法有机改性，即先采用乳液共混法制备出粘土／丁苯橡胶复合物，然后采用机械共混的方式将有机改性剂加入到上述复合物中，经过混炼硫化，得到熔体法有机改性的粘土／丁苯橡胶纳米复合材料。对比考察了十六烷基三甲基溴化铵(C16)、γ-氨丙基-三乙氧基硅烷(KH550)对复合材料结构和性能的影响，发现两种改性剂都可以改善粘土与橡胶之间的界面结合，提高复合材料的力学性能，不同的是C16与橡胶大分子之间为物理缠绕作用，这种物理缠绕只是对提高复合材料的拉伸强度有帮助，而氨基硅烷偶联剂KH550却与橡胶大分子和粘土之间形成化学界面结合，可以同时提高复合材料的定伸应力和拉伸强度，改性效果更好。然后进一步详细考察了硅烷偶联剂KH550和双-(γ-三乙氧基硅基丙基)四硫化物(Si69)的用量对复合材料结构与性能的影响，结果表明，随着硅烷偶联剂用量的增加，复合材料的定伸应力增大，但断裂伸长率下降，从而导致拉伸强度先增大后减小。硅烷偶联剂的最佳用量为4phr，就改性效果来看，KH550要优于Si69。第二种改性方法为乳液法有机改性，即有机改性是在乳液混合絮凝前进行。这种改性方法为作者首创，可以显著改善复合材料的界面，提高复合材料的力学性能。具体改性过程为，先向粘土的水悬浮液中加入有机改性剂对粘土进行有机改性，然后将有机改性后的粘土水悬浮液与丁苯橡胶乳液混合，加入絮凝剂破乳，经干燥、混炼和硫化，得到乳液法有机改性的粘土／丁苯橡胶纳米复合材料。这里主要采用长链烷基季铵盐和硅烷偶联剂作为改性剂，详细考察了改性剂的种类、用量对复合材料结构与性能的影响，并对乳液法有机改性的机理进行了深入的讨论。研究发现，在粘土水悬浮液中，改性剂可以通过离子交换反应吸附到粘土片层上，提高粘土片层的有机性质。加入絮凝剂破乳时，有机改性剂与絮凝剂均可以插入到粘土片层之间，二者存在一定的竞争。当有机改性剂用量较大时，可以完全取代絮凝剂离子插入到粘土片层间，并可以导致部分橡胶大分子对粘土片层的插层，使复合材料中既有改性剂插层结构，又有橡胶大分子插层结构，这样就改善了粘土在橡胶基体中的分散，同时提高了二者的界面结合，使复合材料具有优异的力学性能。对比两类有机改性剂发现，长链烷基季铵盐与橡胶之间的作用主要为物理缠绕，而硅烷偶联剂可以在粘土与橡胶之间形成化学界面结合，尤其是当采用KH550和Si69共同改性复合材料时，这种化学界面结合更为牢固。与熔体法有机改性相比，这种改性方法更能有效地提高复合材料的界面强度和力学性能。采用乳液共混法可以制备粘土／橡胶的母胶，向此母胶中加入其它填料，就可以制备粘土与其它填料并用补强的橡胶复合材料。本论文主要对粘土、炭黑并用填充天然橡胶进行了研究，考察两种填料的并用对复合材料结构与性能的影响。研究发现，两种填料在橡胶基体中均达到纳米级分散，且炭黑粒子填补了粘土片层间的空隙。在填料总量一定的情况下，粘土与炭黑并用，可以提高橡胶基体中填料的体积份数，改善复合材料的加工流动性能、动态力学性能以及物理机械性能。更多还原

【Abstract】 "The nano-compositing technique based on separation of clay nano-platelets by rubber latex particles in aqueous clay nano-suspension", (abr. LCM), is a facile and highly effective nano-compounding method brought forward by Dr. Zhang Li-Qun. Especially, LCM is considered as one of the most important methods to prepare layered silicate/rubber nanocomposites. In this paper, clay/rubber nanocomposites (i.e. MMT/SBR, NR nanocomposites) were prepared through LCM, while the interface of the nanocomposites was carefully designed by introducing various organic modifiers, in order to improve both the clay dispersion and inter facial adhesion of the nanocomposites, and above all, to improve the mechanical properties of the nanocomposites. In addition, the combined effect of nano-clay and nano-carbon black on the properties of rubber (NR) nanocomposites was investigated to provide useful results relevant to the industrialization of clay/rubber nanocomposites.In this paper, mainly two modification methods were adopted to tailor the interface of the clay/SBR nanocomposites. The first one was melt organic modification, in which the clay/SBR nanocomposites were prepared firstly through regular LCM, and then the organic modifiers were added to the nanocomposites during the conventional melt compounding. After blending on the mixers and vulcanization, the final clay/SBR nanocomposites with improvements on the interfacial adhesion were obtained. The effects of C16 (hexadecyl trimethyl ammonium bromide) and KH550 (3-aminopropyltrithoxy silane) on the structures and properties of the nanocomposites were studied and compared, and it was found that both modifiers could well improve the interfacial adhesion between the clay and rubber, resulting better mechanical properties of the nanocomposites. The difference was that, C16 could only form physical interaction with rubber macromolecules that could only benefit the tensile strength of the nanocomposites, but KH550 developed connections between the clay and rubber macromolecules through chemical bonding, which offered much better results from the modification, increasing both the stress at certain strain and tensile strength of the nanocomposites. In second stage, the addition amounts of silane coupling agents (KH550 and Si69: bis-(3-triethoxysilyl propyl)-tetrasulfide) on the structures and properties of the nanocomposites were carefully investigated. The results showed that, with increase of silane coupling agents, the modulus increased, but the ultimate elongation decreased, resulting in better tensile strength at small loading but decreased strength at large loading. The optimum dosage of silane coupling agents was found at 4phr, and it could also be concluded that KH550 gave better outcome of modification than Si69.The second modification method was in-situ organic modification during LCM, invented firstly by author, in which the organic modification was carried out before the co-coagulation step of LCM. This method could well improve the nanocomposite interfaces and increase the mechanical properties of the resulted nanocomposites. In a typical procedure, the organic modifier was added into the clay aqueous suspension to in-situ modify the clay nano-platelets, then mixed the suspension with SBR latex before adding flocculants to co-coagulate clay and rubber. The obtained clay/SBR nanocompounds were dried, further mixed using traditional mixers and vulcanized to give the nanocomposites. Herein, quaternary ammonium salts with long alkyl chain and silane coupling agents were mainly utilized as organic modifiers. The effects of modifier type and loading level on the structures and properties of the nanocomposites were studied, and the modification mechanism was thoroughly discussed. It was found that, in the clay aqueous suspension, the organic modifiers could be adsorbed onto the clay nano-platelets through ionic exchange reaction, in which the originally inorganic clay acquired certain organic characteristics. When the flocculants were introduced into the mixture of modified clay and rubber latex, the organic modifier molecules and flocculants both could be intercalated into the clay galleries, and the competition between the two affected the final structure and properties of the nanocomposites. With relatively large loading of organic modifier, they could be well intercalated into clay layers, rather than flocculants, which then led to the intercalation of rubber macromolecules. Therefore in the final nanocomposites there were modifier intercalated structures and rubber macromolecules intercalated sturetures, which definitely improved the clay dispersion in rubber matrix and the interfacial adhesion. Consequently, the mechanical performance was significantly enhanced. Besides, comparing these two types of organic modifiers, the quaternary ammonium salts could only form physical interaction with rubber macromolecules, while silane coupling agents helped to construct chemical linked interface, particularly with both KH550 and Si69, a quite stronger interfacial adhesion was achieved. The in-situ modification was found to be more efficient in promoting the interfacial interaction and mechanical properties of the nanocomposites than the first method, melt organic modification.Finally, in application studies on the clay/rubber nanocomposites prepared by LCM, other nano-filler could be incorporated into the master batch to give the joint reinforced rubber nanocomposites. In this paper, the combined effects of nano-clay and nano-carbon black on the properties of rubber (NR) nanocomposites was systematically investigated. The results showed that two nano-fillers were uniformly dispersed in the NR matrix at the nano-scale, and the carbon black particles filled into the space between clay layers. At the same total filling amount, combining clay and carbon black could increase the filler volume fraction in the nanocomposites, improve the processability, dynamic and mechanical properties of the nanocomposites.更多还原