Die emulsionscopolymerisation von tetrafluorethylen mit propylen bei niedrigen temperaturen

Abstract

Tetrafluoroethylene and propylene were copolymerized in emulsion at low temperatures (≈25°C) by use of a redox catalyst containing ammonium peroxodisulfate, ferrous sulfate, ethylenediaminetetraacetic acid (EDTA) and hydroxymethane sulfinate. The kinetical study suggested that the working mechanism of the catalyst conforms the following scheme: where the reduction of the ferric ion seems to be rate determining (i.e. k1 ≫ k2) and the hydroxyl ion plays an important role. The overall polymerization reaction is supposed to proceed according to the Case I of the Smith‐Ewart theory under the experimental conditions examined.

A 19F NMR Signal Assignment and a Detailed Structural Study of Alternating Tetrafluoroethylene-Propylene Copolymer by High Resolution 19F NMR Spectroscopy and Computational Chemistry

“…The theoretical calculated peak positions of gtg conformer well explain the experimentally obtained peak positions for both meso and racemic configurations. Compared with theoretically calculated and experimentally obtained peak positions, the signals of (1,(2)(3)(4)8) are assigned to the gtg conformer of racemic configurations and the signals of (1,(3)(4)(5)6) are assigned to the gtg conformer of meso configurations. Consequently, the population of the gtg conformer is larger than that of the other conformers for both meso and racemic configurations at room temperature.…”

“…These cross peaks come from the 3 J couplings between AB and XY pairs. Consequently, two (AB-XY) pairs which are (1,(2)(3)(4)8) and (1,(3)(4)(5)6) exist. These two (AB-XY) pairs are assigned to meso or racemic configurations, respectively.…”

“…TFE-P copolymers possess typical characteristics of this group of elastomers excellent heat resistance, exceptional chemical resistance especially to bases and amines, high electrical resistivity and good mechanical properties. 1,2 Basic studies on the synthesis, structure and properties of these elastomers were carried out by Japanese researchers [3][4][5][6][7][8][9] and they were commercialized by Asahi Glass Co. as Aflas Ò elastomers. The microstructure of TFE-P copolymers has been analyzed by 1 H and 19 F NMR.…”

Initiation of RAFT Polymerization: Electrochemically Initiated RAFT Polymerization in Emulsion (Emulsion eRAFT), and Direct PhotoRAFT Polymerization of Liquid Crystalline Monomers

“…Drawing on the approach used in redox-initiated RAFT, the Fe 2þ species can then reduce APS, being oxidized back to Fe 3þ in the process. [35,36] This mediated reduction of APS also has the advantage that the initiator is activated and radicals are generated in the continuous aqueous phase as in conventional emulsion polymerization, rather than at the electrode surface. These factors were anticipated to promote initiation of polymerization and limit passivation of the working electrode by initiatorderived radicals as observed previously in eRAFT when using exogenous radical initiators.…”

Cure Systems for Fluoroelastomers

“…[42] The initiation system, consisting of ammonium persulfate, ferrous sulfate, ethylene diamine tetraacetic acid (EDTA), and sodium hydroxymethanesulfinate, allows attainment of number average molecular weights above 100,000 Daltons. [42] The initiation system, consisting of ammonium persulfate, ferrous sulfate, ethylene diamine tetraacetic acid (EDTA), and sodium hydroxymethanesulfinate, allows attainment of number average molecular weights above 100,000 Daltons.…”