(A) study on the particle formation and kinetics in the emulsion polymerization of tetrafluoroethylene

Abstract

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semi-batch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). In order to understand the particle formation and kinetics in the emulsion polymerization of tetrafluoroethylene, the polymerization rate, polymer molecular weight, particle formation, and thermal properties and crystalline behavior of polytetrafluoroethylene (PTFE) was investigated over the various reaction conditions. The effects of the reaction conditions were investigated though the polymerization rate, molecular weight of PTFE, and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between $3.48 × 10^{-3}$ and $32.48 × 10^{-3}$ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the reaction temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. The effects of the reaction condition on particle formation investigated. Two different shapes of PTFE dispersion particles were formed by the emulsion polymerization: 1) rods and 2) spherical particles. Variables except for surfactant concentration do not affect the initial a...