Effect of latex and pigment volume concentrations on suspension and consolidated particle packing and coating strength

Packing in the wet state of a suspension of pigment particles at afixedvoltune concentration is of.fected by the threshold addition of latex binder, provided the particle size of the admixed particles is siifficiently similar. The resulting consolidated dry structure displays shrinkage resistance, resulting firom the spacing effect of high-T-g latex. This study investigates a range of pigment and latex volume concentrations, providing a means of extrapolating the combined independent concentrations. Increasing pigment content leads to increased sensitivity to latex volume concentration. The progression toward consolidation follows an exponential viscous (disruptive) response to the presence of latex spheres and supports the observed resistance to capillarit y-induced shrinkage by the correct choice of latex particle size and hardness in relation to pigment packing void size. Using mercury porosimetry, it is shown that the critical disruption point for latex addition in the wet state leads to a complete closure of the pore structure in the dried state. These findings have been correlated with a discontinuity in the breaking elongation of a coated substrate as a function of amount of latex. Therefore, the critical pigment volume concentration can be predetermined in the wet state by the extrapolation of low-shear rheological data, given that the particles involved are of similar size. Hence, the degree of shrinkage resistance can be fornulation-controlled and the degree of coating strength determined.