MICROEMULSION AND EMULSION POLYMERIZATION OF BUTYL ACRYLATE .1. EFFECT OF THE INITIATOR TYPE AND TEMPERATURE

Oil-in-water-type (o/w) microemulsion and emulsion polymerizations of butyl acrylate (BA) initiated by ammonium peroxodisulfate (AP, a water -soluble radical initiator) and dibenzoyl peroxide (DBP, an oil-solubl e radical initiator) with sodium dodecylsulfate (SDS) as an anionic em ulsifier were kinetically investigated. Emulsion polymerizations were faster than those in microemulsion. The rates of emulsion or microemul sion polymerization were larger with AP. The size of particles and the polymer molecular weight decreased with increasing temperature. The n umber of particles and the average particle radical number increased w ith increasing temperature. The overall activation energy (E(o)) for t he BA radical polymerization was found to decrease in the following or der: bulk or solution (ca 120 kJ mol(-1)) > microemulsion (ca 60 kJ mo l(-1)) > emulsion polymerization (ca 15 kJ mol(-1)). The E(o) for the microemulsion polymerization was independent of conversion ca up to 60 %. The strong decrease in the E(0) observed after 60% conversion and t he low value for E(0) in disperse systems were ascribed to diffusion c ontrolled termination.