| Abstract: | When a clay–latex coating, dried below the minimum film-forming temperature (MFT) of the latex, was subsequently heated above the MFT, its opacity and brightness were considerably enhanced. The improvement in optical properties was optimum in the latex content range of 20–40 parts per 100 parts of clay. The sintering of the latex particles, brought about by the thermal treatment, increased the average size of the microvoids to a diameter that is optimum for the scattering of light, without significantly affecting the total void content. Data on light-scattering coefficient, porosity, gloss, brightness, and oil permeability are discussed and compared to those of conventional coatings, i.e., of coatings dried above the MFT of the latex. Similar improvements in optical properties were obtained when coalescence of the latex particles was induced by exposure to a solvent. |
