Solid state 19F NMR determination of new structure formation in FEP following radiolysis at 300 and 363K

Forsythe, John S.; Hill, David J. T.; Mohajerani, S.; Whittaker, Andrew K.

doi:10.1016/s0969-806x(01)00182-7

Cited by 17 publications

(14 citation statements)

References 14 publications

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“…33 The intense signal at F = -122 was attributed to the CF 2 backbone (also found in the NMR spectrum of PTFE). Smaller signals at F = -72 (-CF 3 groups), F = -112 (CF 2 next to CF(CF 3 ) groups), and F = -186 (CF(CF 3 )) were all observed.…”

Section: Solid State Nmr Spectroscopymentioning

confidence: 77%

Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells

2003

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This submission was created using the RSC Article Template (DO NOT DELETE THIS TEXT) (LINE INCLUDED FOR SPACING ONLY -DO NOT DELETE THIS TEXT)Vinylbenzyl chloride was grafted onto PVDF and FEP polymer films using the radiation-grafting methodology. Subsequent reaction with trimethylamine and ion-exchange with potassium hydroxide yields alkaline anion-exchange membranes that are capable of conducting hydroxide ions; such membranes may be suitable for use in low temperature direct methanol fuel cells for portable devices. The PVDF based materials underwent an undesirable degradation and were found to be less suitable for this class of membrane. FEPbased materials exhibited superior structural stability, conductivities up to 0.02 S cm -1 at room temperature, and good retention of ionexchange capacities when treated in water at 60°C.

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Section: Solid State Nmr Spectroscopymentioning

confidence: 77%

Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells

2003

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“…The new signals have been already observed and assigned during previous studies of irradiated perfluorinated polymers. [10,11,[14][15][16][17][18][19] The small signal at À82 ppm is assigned to -CF 3 end groups (-CF 2 -CF 3 ), which are generated as a result of main-chain scission. Short-chain branches (>CF-CF 3 ) as in poly(tetrafluoroethylene-cohexafluoropropylene) (FEP), give rise to signals of -CF 3 side groups (À68, À71 ppm), -CF 2 -groups adjacent to >CF-CF 3 structures (À112 ppm), and >CF-branching points (À184 ppm).…”

Section: Resultsmentioning

confidence: 99%

The Influence of the Irradiation Temperature on the Ratio of Chain Scission to Branching Reactions in Electron Beam Irradiated Polytetrafluoroethylene (PTFE)

Lappan

Geißler

Scheler

2007

Macro Materials & Eng

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Polytetrafluoroethylene (PTFE) films have been irradiated by electron beam in vacuum at various temperatures ranging from room temperature up to temperatures far above the melting temperature. Changes of the chemical structure have been analyzed by 19F solid‐state NMR and IR spectroscopy. The concentration of several structures generated by irradiation increases with increasing irradiation temperature up to the beginning of the thermal degradation. The molar ratio of >CF branching points to CF3 end groups changes with crossing of the melting temperature. The generation of >CF branching points is accelerated if the PTFE is irradiated in the molten state, where branching reactions become more important.magnified image

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“…The spectrum also displays satellites shifted by the rotating frequency from the principal line. Signals from the ter minal -CF 2 -CF 3 or -CF=CF 2 groups, which are present in the commercial PTFE [8], were not observed in the spectra of the composite. It should be noted that the yield of the polymer in the postradiation low temperature polymerization of TFE in the pres ence of MEGO is four to six times that in the case of pure TFE, other conditions being the same (table).…”

Section: Resultsmentioning

confidence: 99%

An NMR, DSC, and IR spectroscopy study of the composite formed during low-temperature postradiation polymerization of C2F4 in the presence of a 3D graphene material

et al. 2013

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By solid state magic angle spinning nuclear magnetic resonance spectroscopy (NMR), differen tial scanning calorimetry (DSC), and IR spectroscopy, polytetrafluoroethylene (PTFE) samples obtained by low temperature (T = -196°C) postradiation polymerization of tetrafluoroethylene (C 2 F 4 ) and C 2 F 4 mix tures with a 3D graphene material formed by the microwave exfoliation of graphite oxide films (MEGO) have been investigated. It has been shown that the melting point of PTFE in the PTFE-MEGO composite is 332.5°C, which is 8.8°C above the melting point of pure PTFE obtained under the same conditions. Accord ing to the measured values of specific enthalpy of melting ΔH m (51.5 and 45.4 J/g), the degrees crystallinity (x c ) of 0.63 and 0.55 have been calculated for the pure polymer and the composite, respectively. It has been also found that none of the PTFE containing samples examined has terminal CF 3 groups typical of PTFE prepared by conventional suspension polymerization.

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Solid state 19F NMR determination of new structure formation in FEP following radiolysis at 300 and 363K

Cited by 17 publications

References 14 publications

Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells

Alkaline anion-exchange radiation-grafted membranes for possible electrochemical application in fuel cells

The Influence of the Irradiation Temperature on the Ratio of Chain Scission to Branching Reactions in Electron Beam Irradiated Polytetrafluoroethylene (PTFE)

An NMR, DSC, and IR spectroscopy study of the composite formed during low-temperature postradiation polymerization of C2F4 in the presence of a 3D graphene material

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