Lee JD, Yang SM
Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, 373-1, Kusong-dong, Yusong-gu, Taejon, 305-701, Korea
J Colloid Interface Sci. 1998 Sep 15;205(2):397-409. doi: 10.1006/jcis.1998.5651.
The rheo-optical behaviors and suspension stability of silica particles coated with silane coupling agents were investigated experimentally. Mono-dispersed silica particles were synthesized by the sol-gel method and the particles were coated with silane coupling agents such as vinyltriethoxy silane (VTES) and gamma-methacryloxypropyl triethoxy silane (MPTES). Although all the suspensions of identical particle volume fraction exhibited similar rheological behaviors at high shear rates, only the stabilized suspensions coated with either VTES or MPTES displayed smooth shear thinning rather than abrupt change in the shear viscosity, as is typical of suspensions with no surface treatment. The present study showed that the MPTES coating was very effective in enhancing the phase stability compared to the VTES coating. The flow-induced dichroism for the MPTES-coated suspensions did not experience sign change, while those of the non-stabilized suspensions changed sign as the shear rate was increased. The VTES-coated suspensions underwent a transition from a stable to an unstable state as the particle volume fraction increased. Specifically, the rheological behaviors of the VTES-coated suspensions of particle volume fraction 0.35 were similar to those of the MPTES-coated suspensions. When the volume fraction exceeded 0.45, however, the effect of VTES coating diminished. Finally, the stress-optical rule proposed by Bender and Wagner was adopted to model the stabilized suspensions considered here. The present results indicated that the stress-optical coefficient could be predicted successfully by the proposed stress-optical rule if the contribution from the hydrodynamic interaction is considered separately from the thermodynamic contribution. Copyright 1998 Academic Press.
对涂有硅烷偶联剂的二氧化硅颗粒的流变光学行为和悬浮稳定性进行了实验研究。通过溶胶 - 凝胶法合成了单分散二氧化硅颗粒，并使用乙烯基三乙氧基硅烷（VTES）和γ - 甲基丙烯酰氧基丙基三乙氧基硅烷（MPTES）等硅烷偶联剂对颗粒进行包覆。尽管相同颗粒体积分数的所有悬浮液在高剪切速率下表现出相似的流变行为，但只有涂有VTES或MPTES的稳定悬浮液表现出平滑的剪切变稀，而不是像未进行表面处理的悬浮液那样剪切粘度突然变化。本研究表明，与VTES涂层相比，MPTES涂层在增强相稳定性方面非常有效。MPTES包覆悬浮液的流动诱导二色性没有发生符号变化，而非稳定悬浮液的流动诱导二色性随着剪切速率的增加而发生符号变化。随着颗粒体积分数的增加，VTES包覆的悬浮液从稳定状态转变为不稳定状态。具体而言，颗粒体积分数为0.35的VTES包覆悬浮液的流变行为与MPTES包覆悬浮液相似。然而，当体积分数超过0.45时，VTES涂层的效果减弱。最后，采用Bender和Wagner提出的应力 - 光学规则对这里考虑的稳定悬浮液进行建模。目前的结果表明，如果将流体动力学相互作用的贡献与热力学贡献分开考虑，则可以通过提出的应力 - 光学规则成功预测应力 - 光学系数。版权所有1998年学术出版社。
