Many commercial products use non-Newtonian rheology to provide stability against sedimentation of important active ingredients, including pharmaceuticals and cosmetics. Unfortunately, these altered theologies only provide a delayed collapse of the product’s stability because they slowly compress and then suddenly collapse over long times scales close to the shelf-life of the product. There is no reliable model of such systems’ collapse kinetics and no way to link the stability to manufacturing parameters like microrheology. This project could adapt existing models of colloidal gel collapse that only incorporate bulk rheological terms and include microrheological parameters that can be linked to processing parameters like mixing speed or pressure drop during homogenization.
- Colloidal gel collapse: Buscall, R. et al. Towards rationalising collapse times for the delayed sedimentation of weakly-aggregated colloidal gels. Soft Matter 5, 1345–1349 (2009).
- Microrheology: Caggioni, M., Spicer, P., Blair, D., Lindberg, S. & Weitz, D. Rheology and microrheology of a microstructured fluid: The gellan gum case. J. Rheo. 51, 851 (2007).
Another aspect of this project involves vibration of products during transport. Fluid products with suspended active ingredients, like shampoos, liquid soaps, and some soft drinks, are often quite stable for long shelf-lives but fall apart quickly after a short trip across town on a bumpy road. The loss of stability is a huge problem for many companies, as it threatens the robustness of products during transport and complicates new product development. (in collaboration with US Procter & Gamble Company)
- Prepare model fluids with known microstructural length scales and examine their collapse kinetics via microscopy.
- Models with updated descriptions of instability kinetics can then be developed and used to design products
- Use high-speed imaging to study the failure of product stability during controlled vibrations