纳米粉体在橡胶基质中的聚集和分散研究

【作者】 林桂；

【导师】 张立群；

【作者基本信息】 北京化工大学 ， 材料学， 2004， 博士

【摘要】 本论文分两个部分:第一部分:利用纳米粉体填充橡胶复合材料,使其发挥纳米粉体对橡胶增强效应及其他特殊的功能,考察填料分散结构和复合材料性能之间的关系显得尤为重要。本论文对纳米粉体填料在橡胶基体中聚集动力学、填料在橡胶基体中的分散和增强效应及其在橡胶制品坦克履带着地胶中应用、填料分散和抗菌性能的影响等方面进行了研究,主要归结如下:纳米填料/橡胶混合体系中填料网络结构在热停放状态下的演变:提出采用低频率低应变下橡胶混合体系的储能模量G’0用来表征纳米粉体在基体中的填料网络结构;采用橡胶加工分析仪在线跟踪了混合体系在热存储下的填料网络结构的演变行为。在SiO2/SIR和SiO2/EPDM体系中纳米填料填充复合材料在初始几千秒内动态储能模量迅速恢复并逐渐达到平衡。模量恢复速率和填料用量具有良好的线性关系。填料网络结构的恢复速度对温度的依赖性较小,压力对SiO2/SIR体系的模量恢复没有影响,而SiO2/EPDM随压力的增大填料网络聚集加强。硅烷偶联剂改性纳米二氧化硅提高了其在橡胶基体当中的分散和稳定。透射电镜和结合胶等测试手段证实纳米填料填充橡胶复合材料在热停放过程中的模量恢复动力学过程是纳米填料絮凝和结合胶增加二者共同作用的结果。纳米填料在橡胶基质中的分散与增强效应:纳米二氧化硅表面富含有硅羟基,在非极性橡胶中自身有很强的聚集力和弱的填料-橡胶相互作用力,因而很容易产生聚集倾向。采用分散剂(含铵基的丙烯酸盐B52)、硅烷偶联剂TESPT、分散剂和TESPT并用改性纳米二氧化硅来增强EPDM,制备具有填料分散度和填料-橡胶相互作用等不同微观结构的复合材料,讨论了填料对复合材料增强能力,以及复合材料性能(动态力学性能)与微观结构之间的关系。结果表明:分散剂能提高二氧化硅在EPDM这种非极性基体当中的混合和分散,但并没有提高填料-橡胶作用,释放出非流动胶,降低硫化<WP=5>胶的模量。添加TESPT也能提高二氧化硅在EPDM基体中分散,同时提高二氧化硅-橡胶作用。TESPT和分散剂并用能进一步提高二氧化硅的分散和填料-橡胶间作用,从而提高纳米粉体的增强效应。填料分散程度的提高和填料-橡胶作用的加强有利于硫化胶的滚动阻力的提高;而抗湿滑性能的提高主要归功于填料-橡胶作用的加强。纳米二氧化硅增强EPDM在坦克履带着地胶(TTRP)中的应用:使用高分散的纳米白炭黑,采用TESPT原位改性分散技术,并通过各种配合体系的精心设计,获得了符合美军标主要技术指标要求的TTRP,某些指标还有明显的超出。同时,使用加入较多量ZDMA的TTRP胶料的胶浆作为粘合过渡层等方式,基本上成功地解决了EPDM难粘合的问题。因此,纳米二氧化硅/EPDM基TTRP可以作为我军新一代主战坦克用的高性能TTRP来使用。纳米二氧化钛/橡胶复合材料的分散结构与性能:新型纳米TiO2(BT)纳米二氧化钛可以提高丁腈橡胶(NBR)橡胶复合材料的硫化活性,却一定程度上延迟了天然橡胶(NR)复合材料的正硫化时间。Degussa 纳米TiO2(DT)对NR硫化特性基本没有影响。两种纳米TiO2在NR、NBR等基体中已达到纳米级分散,形成的聚集体的尺寸小于或接近于100nm,但BT在天然橡胶基体的分散度明显优于DT,与原生颗粒大小相近;纳米二氧化钛添加到橡胶复合材料中起到良好的抗杀菌作用,而且随着纳米二氧化钛含量的增加,其杀菌性能明显提高。BT的杀菌效果与DT的杀菌效果相当。在研究的范围内(0~5phr),纳米二氧化钛/橡胶复合材料的物理机械性能随纳米二氧化钛含量的增加变化不大;纳米二氧化钛对橡胶复合材料的老化性能基本没有影响;热氧老化并不影响复合材料中纳米二氧化钛的抗菌性能。本论文第二部分研究了短纤维增强橡胶发泡复合材料的微观结构与性能的关系,并对其性能进行预测。实验中分别制备了橡胶发泡体(MF)、未处理短纤维增强的橡胶发泡体(MFUS)、预处理短纤维增强的橡胶发泡体(MFPS),观察了气体泡孔和短纤维在橡胶发泡复合体中的微观形态,都得到泡孔分布均匀的发泡复合体,模压工艺使得短纤维在基体中呈现为二维平面分布,未处理的短纤维周围有气泡包围,处理过的短纤维与橡胶间粘合良<WP=6>好;并对它们对复合体的拉伸增强机理及破坏失效机理的影响进行了分析,添加短纤维能有效地提高发泡复合材料的100%拉伸应力和拉伸模量,撕裂强度有所提高,拉伸强度却提高不大。本文还考察了泡孔和短纤维在复合材料压缩过程中行为特征及其对破坏失效机理的影响,添加短纤维能有效地提高发泡复合材料的压缩强度和压缩模量。最后对橡胶发泡复合体的拉伸模量和压缩模量与聚合物发泡体模量预测模型进行了比较,MF的模量和简单混合模型符合较好,而模压成型获得的短纤维增强橡胶发泡复合体(MFPS和MFUS)与常用的简单混合模量预测模型、平方预测模量模型不能很好符合。经过修正的简单混合模型能较好地预测相对密度较低于0.7的MFPS的相对压缩模量,而修正的Halpin-Kerner模型能较好的预测相对密度高于0.7的MFPS的压缩模量。更多还原

【Abstract】 This thesis contains two parts: Firstly, the research works focus on the agglomeration kinetics of nano-inorganic powders filled rubber composites, the relationship of the dispersion of filler and the reinforcement, and the application of nano-silica filled EPDM compounds in the tank-tracked pad. The relationship of dispersion of nano-titania and antimicrobial property of rubber composites are also investigated. Secondly, the research works focus on the reinforcement of short fibers in the microcellular rubber foams.The agglomeration kinetics of nano-silica filled rubber:The properties such as modulus of nanofiller filled rubber compounds are remarkably influenced by the extent of the filler microdispersion. The present work focuses on the microstructure evolution of nanofiller filled rubber composites during thermal annealing. It is found that the modulus at small strain amplitude and low frequency Go’ can be used to evaluate the microstructure of nanofiller filled rubber composites since it is sensitive to the microstructure. Times of wide-range strain sweeps technique is applied before the modulus kinetics testing to avoid the various dispersions of nanofillers in the rubber matrix. Experiment techniques such as transmission electron microscopy, bound rubber measurement are also applied to confirm the change of microdispersion of the nanofiller in the rubber matrix and nanofiller-polymer interactions. The experiment results show that the logarithm of the modulus Go’ grows linearly with the logarithm of time at the initial thousands of seconds. The correlation between the bound rubber and flocculation of nanofiller is also studied. The experiment results indicate that the agglomeration of nano-silica aggregates and the increasing bound rubber are responsible for the modulus recovery of nanofiller filled rubber matrix during thermal annealing. A filler networking <WP=8>mechanism, wherein the silica aggregate bridged by the immobilized shell layer and free polymer chains and the filler-filler network densified by nanofiller’s agglomeration, is proposed to explain the experiment results observed.The dispersion and reinforcement of nano-silica filled EDPM:As silica easily agglomerates in nonpolar rubber due to the strong filler-filler and weak filler-rubber interactions, a dispersant-an alphatic salt containing amine groups and carboxylic groups is used to study effect of the filler-filler and filler-rubber interactions on the reinforcement of silica as well as the dynamic properties of the compounds, in comparison with a traditional silane coupling agent-bis(triethoxysilylpropyl) tetrasulphide (TESPT). The experimental results indicate that incorporation of the dispersant leads to a reduction in the extent of particle agglomeration but also lowers the modulus of the composites by decreasing the adhesion between filler and rubber, while the introduction of TESPT improves the dispersion of silica but also strengthens filler-rubber interactions, therefore leads to a increase in reinforcing potential of the filler. Greater improvement in the dispersion of filler and filler-rubber interactions is obtained when TESPT is adopted to modify silica together with the dispersant. The results also suggest that the strengthened interfacial interaction are the primary contributor to the improved wet traction of the composites, and that both the improved dispersion of filler and the strengthened filler-rubber interactions are mainly responsible for the lowered rolling resistance.The application of nano-silica filled EPDM rubber composites in tank-tracked rubber pads:Tank-tracked rubber pad (TTRP) with excellent mechanical properties, which well meets with the requirement of the novel tanks, is obtained using the formula of nano-silica filled ethylene-propylene-diene terpolymer (EPDM) “in-situ” modified by silane coupling agent. The EPDM rubber composites have good bonded with the metal pad by incorporating dimethacrylic acid zinc salt.The dispersion and antimicrobial properties of nano-titana filled rubber composites更多还原