ESR investigation of ion beam irradiated polyethylene

Tirnovan

Surface & Interface Analysis

et al. 2006

Self Cite

In this paper, we have studied the structure and the phase transformations in thin films (obtained by evaporation from g-irradiated polyethylene bulks -ageing polymer) before and after laser irradiation. We made a comparison between the following samples: A -thin films obtained from g-irradiated polyethylene bulk and not subjected to laser irradiation; B -thin films obtained from g-irradiated polyethylene bulk and subjected to laser irradiation. We have revealed many modifications in the dielectric and structural properties of the thin films, depending on the dose, dose rate and the time of laser irradiation (in the case of samples B). The thickness of all deposited films was 90 nm. The samples (non-irradiated or irradiated) were analysed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), in combination with selected area electron diffraction (SAED). We have also presented the structure of non-aged and non-irradiated thin polyethylene films (control polyethylene film), in which we observed a particularly puzzling phase between an incipient spherulitic phase and a fine structure of the spherulitic phase (specifically for thin PE films structure). After g-and laser irradiations, we observed a strong modification of the structure. The spherulitic phase was transformed. We observed large, amorphous, transparent crystals containing many defects, carbon precipitates, the beginning of crystallisation revealed by electron diffraction, treeing and breakdown figures (usually after laser irradiation).

Section: Discussionmentioning

confidence: 99%

Electron microscopy of γ‐irradiated polyethylene

Tirnovan

Surface & Interface Analysis

et al. 2006

Self Cite

Polymer Degradation and Stability

“…Since we are dealing with an amorphous polymer, the absence of hyperfine structure cannot be attributed to the de localized single electrons of ethylenic and/ or aromatic free radicals. 16 Quantitatively, the variation of the number of spins per g of resin as a function of the integrated dose is shown in Fig. 7.…”

Section: Bulk Sample Characterizationmentioning

confidence: 99%

Gamma-ray-induced modifications of the chemical structure of an ion exchange resin

Draye

Nsouli

Allali

et al. 1997

Gamma-ray irradiation of ion exchange resins used for processing nuclear effluent may lead to considerable modifications of the molecular structure and macroscopic properties. In the present study, crosslinked poly(4-vinylpyridine) (P4VP), irradiated by a 137Cs y-source up to an integrated dose of 14 400 kGy, has been investigated. The particle-induced desorption-mass spectrometry (PDMS) technique is able to detect the radiation-induced structural degrada tion of such an infusible and insoluble material. From the results of PDMS, a coherent description of the production of specific radical fragments and modified chains is proposed. Both the nature of these fragments as well as their formation, as a function of the dose of irradiation, correlate with results of electron paramagnetic resonance spectrometry and Fourier transform infrared spectroscopy, and with thermogravimetric and dynamical mechanical analysis. In addition, analysis of the soluble and insoluble fractions helps to discriminate between different possible processes. In particular, it is shown that the loss of pyridine fragments correlates well with chemical measurements like the loss of protonatable sites.

“…In addition to its high concentration of hydrogen atoms, lightweight, and reduced radiation-induced activation, HDPE may be used as a structural material due to its good mechanical properties and high radiation stability. It is expected that low temperature irradiation (below the glass transition of HDPE) may result in a dominant scission degradation induced (because the diffusion of free radicals is hindered) [4]. It is expected that low temperature irradiation (below the glass transition of HDPE) may result in a dominant scission degradation induced (because the diffusion of free radicals is hindered) [4].…”

Section: Introductionmentioning

confidence: 99%

Proton Beam Induced Modifications in Multi-Functional Polyethylene-Based Carbon Nanotubes Composites

et al. 2004

The space applications of composites obtained by dispersing carbon nanotubes within highdensity polyethylene are analyzed. Electron spin resonance investigations on proton-irradiated composites are reported. The effect of ionizing radiation of the parameters of electron spin resonance spectra is studied. A radiation-induced increase of the concentration of uncoupled electronic spins delocalized over the conducting domains of carbon nanotubes is reported. It is concluded that radiation-induced modifications in such composites are weak.