Surfactant-free emulsion polymerization of chlorotrifluoroethylene with vinylacetate or vinylidene fluoride

A surfactant-free emulsion process has been developed for the preparation of copolymers of chlorotrifluoroethylene with vinylacetate or vinylidene fluoride. A redox initiator system, consisting of sodium-meta-bisulfite, t-butylhydroperoxide, and ferrous sulfate heptahydrate, has been found to be effective in preparing self-emulsifying fluoropolymers with a monodisperse particle size distribution, having up to 45% polymer solids in water. Over the range studied in this investigation, the particle number and the ultimate particle size is linearly related to the quantity of initially charged redox catalyst. Under conditions of optimal catalyst concentrations, a greater number of particles is produced in the surfactant-free process than that which can be obtained using conventional fluorosurfactants. Particle number is defined at the earliest stage of polymerization and remains constant throughout the polymerization, unless surfactant is postadded to the surfactant-free latex at a very early stage in the polymerization. The aqueous phases of various latices have been purified by ion-exchange and dialysis, enabling the sulfonic acid-terminated fluoropolymer end groups to be quantified. The highest level of bound sulfonic acid is obtained at elevated temperatures. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2211–2225, 1998