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Electron irradiation induced molecular changes in PMMA : A positron spectroscopy study
Author(s) -
Awad Somia,
Alkureda Tahani,
AbdelHady Esam E.,
Gomaa Mahmoud M.
Publication year - 2021
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.5125
Subject(s) - positron , materials science , fluence , doppler broadening , positron annihilation spectroscopy , positronium , irradiation , spectroscopy , positron lifetime spectroscopy , electron , electron beam processing , atomic physics , annihilation , trapping , radiation , positron annihilation , spectral line , nuclear physics , physics , ecology , quantum mechanics , astronomy , biology
To examine the positron annihilation parameters with regard to microstructural changes, the positron annihilation lifetime spectroscopy and measurements of the Doppler broadening of annihilation radiation (DBAR) of electron‐irradiated poly(methyl methacrylate) were carried out at room temperature. Trapping rate equations were applied in terms of the positron bulk lifetime as well as the positron lifetime fitting results to investigate the molecular changes due to electron irradiation effects. It was found that the mean positron lifetime shows the same trend as the o‐Ps intensity. In disordered regions, the positronium trapping rate suggests that trapping of o‐Ps increases with increasing electron irradiation fluence until electron fluence reached 5.9 × 10 13 electrons/cm 2 , after which it begins to decrease. The line shape S‐parameter was found to have similar behavior as the o‐Ps intensity, and suggests that poly(methyl methacrylate) undergoes chain scission, followed by cross‐linking, and eventually degradation, due to the electron radiation effects. The results of positron annihilation spectroscopy were verified by X‐ray results, mechanical, and electrical measurements.