EFFECT OF AMOUNT OF EMULSIFIER ADDED IN THE 2ND-STAGE ON MORPHOLOGY OF COMPOSITE LATEX-PARTICLES

In this article, PBA/P(MMA-crosslinking agent)-composite particle late xes were prepared by semicontinuous seeded emulsion polymerization. To determine the seed emulsion's saturating capacity of an emulsifier, a mathematical model was built to simulate the changes of the seed PEA emulsion's surface tension with the amount of emulsifier added dropwis e. The effects of the emulsifier amount added in the second stage and the addition method on the morphology of the composite particles were studied. The results were shown as follows: If the amount of emulsifie r added in one batch to the seed emulsion in the second stage was less than or equal to the saturating capacity of emulsifier of the seed em ulsion (Cs), the morphology of the particles was ''core-shell''; other wise, a few particles were of a core-shell structure. However, if shel l materials were preemulsified and added dropwise at an appropriate ra te, the latex particles were still of a core-shell structure, even whe n the amount of emulsifier added to the seed emulsion was greater than the Cs. (C) 1998 John Wiley & Sons, Inc.