Particle growth in butadiene emulsion polymerization, 1. The use of Fremy salt as aqueous radical scavenger

Abstract

AbstractThe kinetics of the seeded emulsion polymerization of butadiene in combination with variable Fremy salt (potassium nitrosodisulfonate) concentrations was investigated in order to monitor non‐steady state kinetics necessary for obtaining information on entry and exit of radicals from latex particles. Fremy salt is used because it is an entirely water‐soluble stable radical that in principle can scavenge water‐soluble radicals produced by a water‐soluble initiator like peroxodisulfate, but allegedly will not interfere with radicals within latex particles. Adequate buffering of the pH is a prerequisite for stable Fremy salt concentrations in time. Emulsion polymerizations in the presence of Fremy salt showed that not all radicals in the aqueous phase of a swollen polybutadiene latex are scavenged. The use of Fremy salt to monitor non‐steady state kinetics in the seeded emulsion polymerization of butadiene in the presence of tertiary dodecyl mercaptan yields no satisfying results. The use of Fremy salt seems to be restricted to systems where the rate of polymerization is strongly influenced by variation in initiator concentration, i.e. the styrene system or the butadiene system in the absence of tertiary dodecyl mercaptan.