Copolymerizations of tetrafluoroethylene and perfluoropropylvinyl ether in supercritical carbon dioxide: Polymer synthesis, characterization, and thermal properties

Abstract

Tetrafluoroethylene (TFE) and perfluoropropylvinyl ether (PPVE) were copolymerized in supercritical carbon dioxide (sc-CO 2 ) with a perfluorodiacyl initiator bis(perfluoro-2-n-propoxypropionyl) peroxide (BPPP). The resultant copolymers with stable perfluoroalkyl end groups were obtained, avoiding the decomposition during processing and applications. Reactivity ratios of TFE and PPVE were first reported. The r TFE and r PPVE values are about 8 and 0.08, respectively. Such parameters are significant for the modification of PTFE through copolymerization of TFE and PPVE. It is found that through increasing the reaction pressure from 8.5 to 25 MPa, while r TFE increases by 12.0%, r PPVE decreases by 9.0%, which should be ascribed to the enhancement of the polarity of CO 2 under high pressures.Because the reactivity of TFE is by two orders of magnitude higher than that of PPVE; on one hand, the copolymerization rate falls rapidly with the decrease of TFE feed ratio; on the other hand, TFE content in the copolymer decreases with the reaction time. All copolymers containing different fractions of PPVE enjoy outstanding thermal stability. The DSC result indicates that there exist two forms of crystals with highly regular molecular arrangement or less ordered chain packing which is disturbed by perfluoropropyl pendants.

2,2‐Bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene copolymers with different compositions: Synthesis, chain and condensed matter structures and optical properties

“…The monomer reactivity ratios are key parameters to affect the composition and sequence distributions of copolymers at a given monomer composition. The monomer reactivity ratios and the relationship between monomer and copolymer compositions of TFE‐PPVE and TFE‐PMVE copolymerization systems were reported elsewhere, 22,23 However, relationships between the monomer and copolymer compositions were only reported by Desimone et al for TFE‐PDD copolymerizations in the supercritical carbon dioxide medium 21,24 …”

Polytetrafluoroethylene fiber fabrication from the continuous melt-spinning process and its properties

“…Post-thermal treatment was applied to further increase the mechanical properties of the PTFE fiber under a nitrogen atmosphere. Based on the previous thermal deposition studies, a temperature of 260 C was selected for 30 min to 4 h. 24,25 Characterization of morphologies…”

Polycarboxylate superplasticizers of acrylic acid–isobutylene polyethylene glycol copolymers: monomer reactivity ratios, copolymerization behavior and performance

“…A controlled/living photopolymerization of styrene (St) and acrylic acid (AA) was performed at room temperature under UV irradiation, and the monomer reactivity ratios were calculated by the methods of Mayo-Lewis [15], Kelen-Tüdös [11], and YBR [16]. In addition to the above-mentioned methods and means, the methods of Joshi-Joshi [17], extended Kelen-Tüdös [18], Tidwell-Mortimer [19], and error-in-variable [13] and the means of UV-vis [20], 13 C NMR [21], 1 H NMR [22][23][24], 19 F NMR [25], FTIR [26,27], elementary analysis [28], and elemental microanalysis [29] are appropriate for the determination of the monomer reactivity ratios at low conversions. In general, based on terminal copolymerization equation, determination of monomer reactivity ratios needs instantaneous mole fractions of monomers in the copolymer and unreacted and instantaneous monomer concentrations [15].…”