Challenges in the Emulsion Co- and Terpolymerization of Vinylidene Fluoride

Abstract

The feasibility of co-and terpolymerizing vinylidene fluoride (VDF) with ethylene (C2) and/or vinyl acetate in an emulsion polymerization process was studied for different C2 pressures, initiator concentration, surfactant concentration, pH, C2 injection protocols and the influence of vinyl acetate (VAc) in the reaction medium. Pressure drop and temperature profiles, as well as gravimetry were used to follow the rate of polymerization. The microstructure of the synthesized products was assessed fluorine and hydrogen nuclear magnetic resonance spectroscopy (19F and 1H NMR). C2 was found to cause an inhibition/retardation effect on the copolymerization with VDF (and with VDF/VAc). However, statistical copolymers containing VAc and VDF were synthesized by reducing as far as possible the homogeneous nucleation of the VAc in water phase. This was done by adding VAc into the reaction after the homogeneouscoagulative nucleation of VDF takes place (around 5 minutes after initiator injection).

Chain-End Functionality: The Key Factor toward Fluoropolymer Thermal Stability

“…11−16 Commercially available PVDF is mainly prepared via either emulsion or suspension process in water, using a fluorinated or nonfluorinated surfactant, initiated by a wide variety of organic peroxides 17,18 or inorganic persulfate initiators. 19−21 These synthetic methods are efficient, but the use of surfactants, such as ammonium perfluorooctanoate (APFO), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS), 22 is a major drawback because of the bioaccumulation, toxicity, and persistence issues. 23 However, the nature of the chain-end functionality was found to be a crucial factor that affects the thermal stability of the polymers via the "Unzipping" thermal degradation.…”