As described in the contract proposal the first phase of work was to:
(i) I prepare and characterise a model dispersion
(ii) develop or evaluate a suitable low stress viscometer
and progress in these in reported in section 2 and 3 of this report. The model dispersion was chosen to consist of well characterised particles in which the degree of flocculation/deflocculation could be controlled by suspension in a fluid whose viscosity could be modified thus altering the shear stresses present for a given strain rate. For reasons previosuly discussed it was decided to use a mono-disperse polystyrene latex as the model dispersion and this report describes how sufficient quantities for rheological experiments were synthesised, worked up and characterised. Work is still proceeding on the characterisation of these latices, particularly to measure their zeta potentials as a function of salt concentration and to determine the effect on this of high sucrose and gylcerol concentrations, these substances being chosen to alter the viscosity of the suspending fluid.
A requirement of the programme of work to be done under this contract is the ability to measure shear stress/strain properties at low strain rates and in oscillation at small amplitudes. To this end the University has purchased a Deer Rheometer and this report gives a preliminary assessment of this instrument. Section 4 of this report is an account of preliminary experiments to study 2 the effect on the viscosity of a calcium carbonate/water/Dispex system of increasing the viscosity of the suspending liquid. The results of this work are discussed in relations to a published suspension flow equation and to a theoretical model of the balance of interparticle and hydrodynamic forces on suspension stability.