Rheological Properties of Silica Suspensions and Visualization of the Network Structures

用轧机将气相二氧化硅分散到丙烯酸单体中。分散颗粒采用二氧化硅气溶胶（A200; Degussa Co.）。粉末直径为12nm，密度为2.2g/cm^3。光敏分散介质是用光敏自由基发生器敏化的两个功能化丙烯酸单体。用计算机辅助流变仪测量了其动态粘弹性特性。所有测量均在25℃的温度下进行。所有悬浮液均表现为典型的剪切变薄。我们可以推断，随浓度变化的絮凝网络结构是通过稳定剪切被破坏的。在无稳态剪切流的情况下，G′与角频率的关系表现出浓悬的特性，即G′与角频率无关。在稳定剪切作用下，用紫外照射对粘膜样品进行聚合，以固定结构。结果表明，根据二氧化硅悬浮液的流变行为估计的剪切网状结构的形成或变形与透射电镜观察结果一致。

Fumed silica was dispersed in acrylate monomer by a roll mill. The silica aerosil (A200 ; Degussa Co.) was used for dispersed particle. The diameter and the density of powder were 12nm and 2.2g/cm^3, respectively. Photosensitive disperse medium was two functional acrylate monomer sensitized with photosensitive radical generator. Dynamic viscoelastic properties were measured by computer aided rheometer with a cone and plate geometry. All measurements were carried out at 25ﾟC.All suspension show typical shear thinning. We can deduce that the flocculated network structure depending on the concentration is broken down by steady shearing. The dependence of on the angular frequency without steady shear flow shows the characteristics of a concentrated suspension, namely the G' is independent of this frequency. After applying steady shear, the viscous film samples were polymerized by UV irradiation for fixing the structure. The results showed that the formation or deformation of the network structure by shearing estimated from the rheologycal behaviors of silica suspension was consistent with the TEM observation.