Abstract: The stability of cationic and anionic polydimethylsiloxane latices towards acid and base was studied. It was found that the anionic latices were stable in the acid of concentration usually employed for catalytical polymerization. The stability of cationic latices was poor towards base, which is used as the catalyst of the polymerization. The limit sodium hydroxide concentration causing slow flocculation of cationic latices was lower than the concentration needed for the polymerization, so that the formation of large latex particles owing to flocculation could not be prevented during the emulsion polymerization. The transfer of a large part of the emulsifier from the aqueous phase to tpolysiloxane phase during the emulsion polymerization was also responsible for the formation of large latex particles.

Key words: emulsion polymerization, octamethylosiloxane, stability, large latex particle