High PVC film‐forming composite latex particles via miniemulsification, part 1: Preparation

Abstract

Miniemulsification technology was used to encapsulate TiO 2 particles inside a styrene/n-butyl acrylate copolymer with high loading levels (11 to 70% PVC (pigment volume concentration)). In this approach, a St/BA copolymer dissolved in toluene in the presence of a costabilizer (hexadecane) was mixed with a dispersion of TiO 2 particles in toluene and sonified, and then emulsified in an aqueous surfactant solution by sonification. The effect of sonification time on both the dispersibility of the TiO 2 particles in the presence of the copolymer and hexadecane and on the encapsulated particle size was investigated. Particle size analysis by dynamic light scattering showed that these composite latexes are quite stable. It was also found that as the TiO 2 loading increased from 11 to 43% PVC, the particle size of the TiO 2 dispersion decreased while the polymerencapsulated TiO 2 particle size increased. The effect of surfactant concentration (sodium lauryl sulfate, SLS) on the encapsulated particle size was investigated using four different SLS concentrations in the 11% PVC system. The results showed that as the SLS concentration increased the particle size decreased, as expected. Also it was found that the minimum surfactant concentration that gives stable encapsulated TiO 2 particles is above 10 mM SLS. The role of HD in the recipe was studied for an artificial latex containing no TiO 2 and one prepared at 11% PVC, in terms of particle size before and after solvent stripping, and its effect on the T g .

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

“…25 The recipe for the preparation of TiO 2 -encapsulated artificial latexes by the direct miniemulsification technique is shown in Table II. The detailed description of the preparation procedure can also be found in the previous paper.…”

“…25 Sodium lauryl sulfate (SLS; Fisher, Pittsburgh, PA), toluene (VWR, Bridgeport, NJ), and hexadecane (HD; Sigma-Aldrich, St. Louis, MO) were used as received. The solid to be encapsulated in this work was TiO 2 (hydrophilic, 30 nm, Degussa, Parsippany, NJ) under the brand name P-25.…”

“…The detailed description of the preparation procedure can also be found in the previous paper. 25 Latexes with varying TiO 2 loadings (11-70% PVC) were prepared. These latexes were used to cast films at different thicknesses, which were then characterized in terms of their optical properties, as will be discussed later.…”