Latex dispersability index

摘要

The pigment loading capacity (PLC) of dispersion binders is an important factor in the formulation of a latex paint. However, there has been no reliable method for the quantitative evaluation of this property; this has led to difficulty in comparing latex binders in this regard. In this article, a new parameter, the latex dispersability index (LDI), is proposed as a quantitative measure of PLC of latex binders. In this test method, the capability of latex to disperse pigments (or extenders) is quantified on the basis of the idea of the minimum viscosity method for dispersants. The face-centered cube experimental design was used to synthesize 26 binders. On the basis of this design, the synthesized latexes had a maximum diversity of properties, especially with regard to PLC. The binders were formulated with three mineral powders (i.e., TiO_2, CaCO_3, and talc). The curves of viscosity versus mass of the resin for all of the samples were prepared. The general trend of the curves was universal and only depended on the nature of the powders. The geometry of the curves and PLC had quantitative correlations. To make a quantitative correlation between the curves and PLC, LDI was defined as a function of the area under the curve, the height of the curve, and the length of the end point. Four ranges of LDI were assigned to the conventional quantitative phrases for PLC. The usefulness of this parameter was then verified by some well-known commercial binders with different PLCs. The results were in a good agreement with the expected behaviors.