Rheology of Colloidal Gels

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.