Composition-viscosity data for polymer thickened aqueous solutions,63 together with reliable theoretical models to predict the effect of the dispersed phase,64 were used to construct equations of the type \(log(\eta)=a+bx_{n}+c\phi\) (average relative error of 22%), for each polymer, and for both \(\eta_{1}\ \)and \(\eta_{2}\) (\(\phi\) is the mass fraction of oil phase). Since only one polymer is used, mixing rules are not needed. Fatty alcohols were used at a 2-4% concentration. As indicated above, all the formulations also included a fixed amount of mandatory ingredients, namely water, humectant (3% Glycerol) and preservative (0.7% Cosgard®).
Optimization problem : Product design variables and short formulation of the optimization problem for both case studies - in the form of (3) - are shown in Table 2.
Table 2. Product design variables and initial problem formulation