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Title: Multiple-scale approach to understanding formulated product production
Author: Rodgers, Thomas Lawrence
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2011
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Consumer- and pharmaceutical-based products are a major component of the chemical industry. In the personal care industry, formulations often consist of a mixture of surfactants and fatty alcohols. The addition of surfactants aids the stability of the formulation. The formulated product microstructure depends upon the preparation conditions as well as the ingredients. Controlling which microstructures form during the production of a formulated product is important as different microstructures can have wildly different physical properties, making some far more favourable than others. This thesis examines several of the processes undertaken in the manufacture of formulated products. The dissolution of a surfactant in a bulk water phase is examined. This is examined in a number of ways; firstly, the dissolution times of the surfactants are measured using electrical resistance tomography. It is found that the dissolution time varies with the agitation rate, agitator size, and addition method. The dissolution is also examined using dissipative particle dynamics to gain insight into the dissolution on a molecular scale. It is found that the surfactant breaks into wormlike micelles on dissolution. If an oil is added to the initial bulk then the dissolution process is modified so that long cylinders are produced with some spherical micelles. Finally, the break-up rate is predicted using a breakage model based on the agitator shear rate and a network-of-zones model. This produces good results. The production and post-shear processing of a sample formulated product, hair conditioner, is examined. Firstly, the mixing in a vessel is examined with electrical resistance tomography. Problems are encountered when the production method involves the use of distilled water as the conductivity is very low; however, the mixing time of the final product in the vessel can be determined. It is also shown that the majority of the structural changes in the post-shearing process are caused by the in-line rotor-stator mixer. The viscosity of the product increases in a linear fashion with the shear rate, while the conductivity increases as a function of the shear rate and the recycle rate. This allows the monitoring of the post-shearing process to be carried out using electrical resistance tomography. This thesis also looks at the possibility of producing a multiple frequency electrical resistance tomography device to monitor formulated product production; however, it has been shown that the conductivity does not vary with the voltage frequency over a usable range. This meant that no further effort was put into developing this, as it gave no advantage over the traditional single frequency technique. Nevertheless, important advances towards better understanding of mixing processes resulted due to the investigations carried out.
Supervisor: Siperstein, Flor Sponsor: Unilever
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Tomography ; Mixing ; Surfactants ; DPD ; NoZ