ESR study of free radicals produced in polyethylene irradiated by ultraviolet light

Abstract

ESR studies of ultraviolet‐irradiated polyethylene (PE) were carried out. Irradiation effects different from those of high‐energy radiation are observed. Ultraviolet radiation is absorbed selectively, and especially in carbonyl groups in PE produced by oxidation. Radicals produced were identified as \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CHO}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CH}_2 \hbox{---}$\end{document}. Some radicals giving a quintet signal stable at room temperature were also observed but remained unidentified. The radical \documentclass{article}\pagestyle{empty}\begin{document}$ \hbox{---} {\rm CH}_2 \hbox{---} {\dot {\rm C}} {\rm H} \hbox{---}{\rm CHO}$\end{document} undergoes a mutual conversion with the acyl radical:

Properties of Nanocomposites Based on Polyethylene (UHMWPE) and Carbon Nanotubes Mixed by High-Energy Ball Milling and UV-Source Irradiated

“…This result is in agreement with Hama et al [16] In Table I are listed the oxidation indexes (OI Carbonyl ) of all the checked polymeric samples (UH0, UH2, UH4, UH6, UH18, UH24). CAMPO AND A. M. VISCO signal, suggesting that C ¼ O is the main oxidized species induced by the UV ray absorption.…”

Photothermal recycling of waste polyolefin plastics into liquid fuels with high selectivity under solvent-free conditions

“…In the case of photothermal recycling of polyolefin plastics, reaction temperatures above the melting point of the plastics (melting temperatures by differential scanning calorimetry (DSC) 25 : 112 °C for LDPE, 138 °C for HDPE, 169 °C for PP) will be beneficial for (1) increasing the mobility of polymeric chains and (2) increasing the contact between the polymers and the photothermal catalyst, thereby improving the probability of C-C or C-H scission processes in the presence of a suitable catalyst 26 . Further, UV irradiation of polyolefins can activate inert polymeric chains and generate active radical species (such as the allylic radicals in the irradiated polyethylene), thereby offering pathways for polymer conversion into other products [27][28][29] . Based on this information, we hypothesized that photothermal recycling of polyolefin plastic wastes into valuable liquid fuels should be possible in the presence of a suitable catalyst with good activity for C-C and C-H scission reactions.…”