Morphological Changes during Preparation of Hollow Latex Particles

摘要

Voided particles derived from multilayer core/shell structures with an alkali-swellable core have gained major commercial importance as opacifiers in coating formulations. In order to control the particle morphology efficiently in such systems, it is important to understand the physical changes brought about in the alkali post-treatment process. In this reported study SEM and TEM were used to investigate the influence of post-treatment temperature, time and initial pH of the latex on particle morphology. The system studied comprised a core derived from MMA (40), MAA (24), BA (35.4), EGDMA (0.6). An intermediate shell was formed from MMA (72), St (20), MAA (8) and finally an outer shell from St homopolymer. A multistage emulsion polymerisation procedure was used to prepare the latex. The core diameter and shell thickness of the final un-neutralised latex were -235nm and -60nm respectively. Ammonia solution was used to post treat the latex at predetermined initial pH and temperature.