Rheology of Colloidal Gels

胶凝剂在学术和工业上都很有意义。事实上，在工业中，它们可以用作增稠剂，防止沉淀，使产品具有更好的均匀性，可以持续更长时间，而不会有微生物变质的缺点，例如。因此，市场上存在着种类繁多的具有不同流变特性的胶凝剂，适用于不同的体系（水基或油基体系）和应用（食品或化妆品）。然而，也有可能通过改变系统中粒子或分子之间的相互作用来调整它们的流变特性。它可以通过使用盐、改变pH值或改变颗粒表面来实现。然而，由于时间对基体的影响，具有理想流变特性的胶凝剂也可以具有一些好处。因此，该项目可以导致凝胶的配方或具有所需流变性能的改性胶凝剂的合成。对这些性质的了解将有助于更好地理解凝胶的结构及其随时间的演变，并可以作为定制凝胶流变学性质的指导。在先正达作为工业合作伙伴的支持下，该项目旨在开发替代胶凝剂或配方，以取代目前使用的胶凝剂或配方，同时符合流变学要求。从学术的角度来看，这个项目的目标是多重的。一个是通过确定老化动力学并试图阻止它来了解无机胶凝化合物随时间的行为。另一个目标是了解为什么它们具有与聚合物化合物相同的流变性能。本项目主要研究使用矿物化合物作为胶凝剂。作为项目的一部分，不同的无机材料将被流变学表征。这些无机材料主要由粘土组成，粘土可以是合成的，也可以是天然的。首先，对市场上已有的粘土进行了调查。那些具有最有前途的特征的将被保留。然后，可以设想几种选择来创建具有与现有的和参考的凝胶相同的流变性能的凝胶。一种是研究凝胶的配方，尝试混合不同的粘土或玩弄盐和/或ph值。另一种选择是通过涂覆来修改选定的粘土，例如调整其流变性能。该项目属于EPSRC物理科学研究领域和繁荣雄心，因为它通过牛津大学和先正达胶体小组的高度参与，将学术目的和行业相关性结合在一起。它还将有助于开发新的系统，这些系统可以在未来被工业使用，以改进产品制造，同时更好地了解产品。

Gelling agents are of interest for both academic and industrial purposes. In fact, in industry they can be used as thickeners preventing sedimentation and allowing a better homogeneity of products that can last for longer without the disadvantage of microbial spoilage, for example. Hence, a huge diversity of gelling agents with different rheological properties exists on the market and are suitable for different systems (water or oil based system) and applications (food or cosmetic). However, it is also possible to tailor their rheological properties by changing interactions between the particles or molecules in a system. It can be achieved by using salt, varying the pH or changing the surface of the particles. Nevertheless, a gelling agent having desired rheological properties can also feature some benefits due to the effect of time on the matrix for instance. Hence, this project can lead to the formulation of gels or the synthesis of modified gelling agent having desired rheological properties. The understanding of these properties will contribute in building a better comprehension of the gel structure and its evolution with time, and could serve as guide to tailor rheological properties of gels. With the support of Syngenta as industrial partner, this project aims at developing alternative gelling agents or formulations to replace the currently used one while complying with rheological requirements. From an academic point of view, the goals of this project are multiple. One is to understand how inorganic gelling compounds behave with time by determining an aging kinetic as well as trying to prevent it. Another goal is to understand why they feature the same rheological properties as polymeric compounds. This project is mainly focused on using mineral compounds as gelling agent. As part of the project, different inorganic materials will be rheologically characterised. These inorganic materials will consist mainly of clays which can be either synthetic or naturals. First of all, clays already available on the market are investigated. The ones having the most promising characteristics will be kept. Then, several options can be conceivable to create a gel having the same rheological properties as the already existing and referenced one. One will be to work on the formulation of the gel, trying to mix different clays or playing with salt and/or pH. Another option will be to modify the selected clays by coating them for example to tailor their rheological properties. This project falls within the EPSRC Physical sciences research area and Prosperity ambition as it contributes in bringing academic purpose and industry relevance together through the high involvement of the Colloid group at the University of Oxford and Syngenta. It will also contribute in developing new systems that could be used in the future by industries to improve manufacturing of products while building a better understanding of them.