Characterisation of instability of concentrated dispersions by a new optical analyser: the TURBISCAN MA 1000
Characterisation of instability of concentrated dispersions by a new optical analyser: the TURBISCAN MA 1000
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DOI：
10.1016/s0927-7757(98)00680-3
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发表时间：
1999-07-15
影响因子：
5.2
通讯作者：
Snabre, P
中科院分区：
文献类型：
--
作者：
Mengual, O;Meunier, G;Snabre, P
乳化液或悬浮液的不稳定通常是由两种物理现象引起的：(1)颗粒尺寸增大（聚结）或颗粒聚集（絮凝）；(2)颗粒迁移（起霜或沉淀）。乳化或沉淀通常被认为是可逆的，而聚并或絮凝则会给配方剂带来灾难。因此，为了缩短老化试验和改进配方，在早期阶段发现这些现象是至关重要的。因此，这项工作涉及集中色散的不稳定的光学特征。它主要处理光的独立和各向异性散射的悬浮液或乳剂在圆柱形玻璃管与光学分析仪TURBISCAN MA 1000。事实上，在密集的悬浮液或乳剂中，光子在逃离介质并进入接收器孔径之前经历了许多散射事件。因此，多次散射对测量的透射通量和后向散射通量有重要贡献。我们提出了仅涉及光子平均路径长度、不对称因子和光接收器几何形状的悬架（平面或圆柱几何）中的辐射传输的统计模型和数值模拟。我们进一步开发了一种高灰度分辨率的成像方法，用于后向散射聚光灯下表面通量的可视化和分析。我们将物理模型和模拟结果与使用成像方法和TURBISCAN MA 1000分析仪进行的乳胶珠分散（可变尺寸和颗粒体积分数）实验结果进行了比较。然后，我们用TURBISCAN MA 1000提出了几个分散不稳定分析的例子。我们表明，该仪器能够区分浓度和颗粒或聚集体大小的变化，并检测到这些现象比操作员的肉眼更早，特别是不透明和集中的系统。(C) 1999 Elsevier Science B.V.版权所有
Emulsion or suspension destabilisation is often due to two physical phenomena:(1) particle size increase (coalescence) or particle aggregation (flocculation);(2) particle migration (creaming or sedimentation).Creaming or sedimentation are often considered as reversible while coalescence or flocculation spells disaster for the formulator. Therefore, it is of prime importance to detect at an early stage these phenomena in order to shorten the ageing tests and to improve the formulations.This work thus concerns the optical characterisation of destabilisation of concentrated dispersions. It deals mainly with the independent and anisotropic scattering of light by a suspension or emulsion in a cylindrical glass tube in relation with the optical analyser TURBISCAN MA 1000. Indeed, in dense suspensions or emulsions, photons undergo many scattering events before escaping the medium and entering a receiver aperture. Multiple scattering thus contributes significantly to the measured transmitted and backscattered flux.We present statistical models and numerical simulations for the radiative transfer in suspensions (plane or cylindrical geometry) only involving the photon mean path length, the asymmetry factor and the geometry of the light receivers.We have further developed an imaging method with high grey level resolution for the visualisation and the analysis of the surface flux in the backscattered spot light.We compare the results from physical models and simulations with those of experiments performed using the imagery method and the TURBISCAN MA 1000 analyser for dispersions of latex beads (variable size and particle volume fraction).We then present a few examples of dispersion destabilisation analysis with the TURBISCAN MA 1000. We show that the instrument is able to discriminate concentration and particle or aggregate size variations and to detect those phenomena much earlier than the operator's naked eye, especially for opaque and concentrated systems. (C) 1999 Elsevier Science B.V. All rights reserved.