On the effect of radiation-chemical and radiation-physical transformations in polytetrafluoroethylene on its dielectric properties

Matveev, V. K.; Klinshpont, E.R.; Surnin, V.A.; Kiryukhin, V.P.; Milinchuk, V.K.

doi:10.1016/0032-3950(90)90152-v

Cited by 1 publication

(8 citation statements)

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“…The mechanism of eq 4B is validated by previous work, , while the mechanism of eq 4D is facilitated by both the radiolysis of molecular oxygen and the decomposition of H 2 O 2 . Equation 4C is confirmed by our observation of CF 2 O which is a verified decomposition product of peroxyl-functionalized fluorocarbon radicals. ,, Generation of atomic oxygen is supported by our data which show an increase in the signal of O - with increasing α dose.…”

Section: Discussionsupporting

confidence: 80%

“…In general, the exponential fits overestimate the signals at low dose and underestimate the signals at high dose. The signal of the CF 2 O + ion, an autolytic decomposition product of peroxyl-functionalized fluorocarbon species, , follows the same trend, as expected. Noteworthy exceptions to this generalization are the signals of oxyl-functionalized fluorocarbon species, C 3 F 4 O + and C 3 F 7 O + .…”

Section: Discussionsupporting

confidence: 79%

“…This conjecture is based on the signals of both F - and F 2 - that decline as a function of α dose and the signals of small fluorocarbon fragments that escalate as a function of α dose. Several studies have implicated a second-order mechanism for the production of oxyl species, ,,,, and we postulate the pathways shown in eqs 4B−D to address these data. The mechanism of eq 4B is validated by previous work, , while the mechanism of eq 4D is facilitated by both the radiolysis of molecular oxygen and the decomposition of H 2 O 2 .…”

Section: Discussionmentioning

confidence: 84%

“…In addition to previous data 7,8 regarding the emergence of hydro-, oxyl-, and peroxyl-functionalized fluorocarbons, we have disclosed evidence demonstrating the production of hydroxyl-functionalized fluorocarbons by way of α particle-initiated reactions between fluorocarbon fragments and molecular gases. We have proposed a set of kinetic expressions that address the prominent features observed in our data without contradicting previously validated reaction mechanisms. − ,− Without question, these mechanisms neglect the intermediate, dynamic processes since we are only able to identify the stable products of reaction and decomposition. Nevertheless, the proposed kinetic expressions provide a basis from which to interrogate systematically the α radiolysis of PTFE in ambient and vacuum atmospheres.…”

Section: Discussionmentioning

confidence: 90%

“…Characteristic fragment ions and their nominal mass-to-charge ratios are CF + (31 m/z), CF 2 + (50 m/z), CF Upon R particle irradiation, changes in the signal of characteristic PTFE fragments were monitored, and new features in the mass spectra were identified and characterized. In most cases, emergent fragments appear in the mass spectra at intervals of 12,16,19,31, and 50 m/z units corresponding to C, O, F, CF, and CF 2 , respectively, whereby we are able to recognize families of related fragments. We have previously shown substantial evidence for the emergence and proliferation of hydrocarbons as well as oxyl-and peroxyl-functionalized fluorocarbon moieties.…”

Section: Resultsmentioning

confidence: 99%

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TOF-SIMS Evidence of Intercalated Molecular Gases and Diffusion-Limited Reaction Kinetics in an α Particle-Irradiated PTFE Matrix

et al. 2006

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The chemical evolution of poly(tetrafluoroethylene) (PTFE) that is brought about by increasing levels of irradiation with alpha particles is accompanied by the emergence and proliferation of functionalized moieties. Families of reaction products specifically identified in the alpha-irradiated polymer matrix include hydride-, hydroxide-, and oxide-functionalized fluorocarbons. The data also indicate the emergence of hydrogen peroxide (H2O2) and hydrazine (N2H4), but no distinct evidence suggesting the formation of perfluorinated amines, amides, or cyanogens is found. In this article we substantiate the speciation of emergent species and reveal evidence of intercalated molecular gases with which alpha particle-generated radicals may react to form the observed products. Furthermore, we present evidence to suggest that the kinetics of alpha particle-induced reaction is limited by the diffusion of radicals within the polymer matrix. That is to say, chemical additives in the polymer matrix are shown to be scavengers of H*, O*, and F* radicals and limit the rates of reaction that produce functionalized fluorocarbon moieties. Above a threshold dose of alpha particles, the concentration of radicals exceeds that of the scavenger species, and free radical diffusion commences as evidenced by a sudden increase in the yield of reaction products. Samples of PTFE were irradiated to alpha doses in the range of 10(7) to 5 x 10(10) rad with 5.5 MeV 4He2+ ions from a tandem accelerator. Residual gas analysis (RGA) was utilized to monitor the liberation of molecular gases from PTFE during alpha particle irradiation of samples in vacuum. Static time-of-flight SIMS (TOF-SIMS), equipped with a 20 keV C60+ source, was employed to probe chemical changes as a function of alpha particle irradiation. Chemical images and high-resolution mass spectra were collected in both the positive and negative polarities.

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