High PVC film‐forming composite latex particles via miniemulsification, part 3: Optical properties

The optical properties of films cast from latexes comprising TiO 2 particles encapsulated in poly(styrene‐ co ‐ n ‐butyl acrylate) prepared by miniemulsification and having high loading (11–70% pigment volume concentration (PVC)) were investigated. Contrast ratio (CR) measurements for all batches showed that a 3 mil film (obtained at 43% PVC) was the minimum thickness at which 98% CR could be achieved. Also, the greatest hiding power (HP) (535 ft 2 /gal) was obtained at 43% PVC. In addition, gloss measurements showed that as the TiO 2 loading increased, the gloss decreased, indicating that the increasing amount of TiO 2 contributed to a reduction in the surface smoothness. The effects of surfactant concentration (sodium lauryl sulfate) on the encapsulated particle size and the optical properties of the encapsulated films for the 11% PVC system are described. The effect of varying the sonifier operating conditions on the TiO 2 particle size, encapsulated particle size, and the optical properties of the encapsulated films for the 43% PVC system was also investigated. A comparative study of the optical properties of films cast from encapsulated latex particles with films cast from physical blends of polymer particles and pigment at the same TiO 2 loading and film thickness was made. The optical properties (i.e., CR and gloss) showed a clear advantage of the miniemulsification process over the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4526–4537, 2006