Zur Bestrahlung gasförmiger Perfluorcarbone. Ein Beitrag zum Mechanismus des strahlenchemischen Abbaus von Polytetrafluorethylen

Abstract

Durch erneute Einwirkung beschleunigter Elektronen auf die gasförmigen und leicht flüchtigen Produkte des strahlenchemischen PTFE‐Abbaus vom Kettenlängenbereich C1 bis C6 in inerter Atmosphäre werden Reaktionen der Kettenverlängerung ausglöst. Die analytischen Befunde beweisen ein stärkers Auftreten kettenverzweigter Produkte. An Hand der Ergebnisse werden einige grundlegende Aspekte zum Reaktionsmechanismus des strahlenchemischen Abbaus von PTFE diskutiert.

Electron beam irradiation of polytetrafluoroethylene in vacuum at elevated temperature: An infrared spectroscopic study

“…In the spectrum of PTFE irradiated with a dose of 0, and the appearance of a third band at 1690 -1680 cm Ϫ1 (OCFACFϽ; i.e., branching at ␣ position) was observed. 18,19 In contrast to these observations, Fisher and Corelli 15 postulated that absorption bands, which were found at 1735 and 1715 cm Ϫ1 , are caused by branched or crosslinked structures.…”

Electron beam irradiation of polytetrafluoroethylene in vacuum at elevated temperature: An infrared spectroscopic study

“…17 Radiationinduced reaction routes forming the olefinic structures are discussed in an earlier work. 20 In some cases, both a splitting into two bands at 1743 cm Ϫ1 /1730 cm Ϫ1 , 18 and 1736 cm Ϫ1 /1722 cm Ϫ1 , 19 and the appearance of a third band at 1690 -1680 cm Ϫ1 (OCFACFϽ; i.e., branching at ␣ position) was observed. 18,19 In contrast to these observations, Fisher and Corelli 15 postulated that absorption bands, which were found at 1735 and 1715 cm Ϫ1 , are caused by branched or crosslinked structures.…”

“…The other three bands, at 1730, 1717, and 1671 cm Ϫ1 , are assumed to be characteristic of olefin formation in the polymer chain because of results obtained in earlier stud-ies of PTFE degradation in nitrogen atmosphere at very high doses. [17][18][19] By this procedure, mixtures of perfluoroparaffins and perfluoroolefins with terminal and internal double bonds were obtained. The IR spectra of these mixtures show a band at 1740 cm Ϫ1 (OCFACFO) in addition to the band at 1795 cm Ϫ1 (OCFACF 2 ).…”

Influence of High‐Energy Ion Irradiation on the Structural, Optical, and Chemical Properties of Polytetrafluoroethylene

“…78 There was a decrease in the absorption of a band at position 2387 cm −1 of the irradiated sample at a fluence of 1 × 10 11 ions/cm 2 . 82 This band dissappeared after irradiation. Similarly, Atta et al 79 observed in their study on PTFE after irradiation by 3 keV argon ions the decrease in the absorption band of 2360 cm −1 (in our case, the same band is at wave number 2387 cm −1 in the pristine sample; this band is assigned to a combination of two modes associated with the CF 2 backbone 80 ).…”

“…The CF 3 branches are formed by a reaction of the chain radical with the mobile CF 3 radical as reported by Dorschner et al 81 A weak absorption band at 1730 cm −1 in the spectrum of the pristine sample is assumed to be characteristic of internal double bonds. 82 This band dissappeared after irradiation. Two bands at positions 1805 and 1796 cm −1 disappeared in the spectrum of irradiated PTFE at a fluence of 1 × 10 10 ions/cm 2 .…”