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EnglishThe radiation-induced oxidative degradation of polyethylenes (PEs) with different degrees of crystallinity was characterized after electron-beam irradiation and during storage at room temperature. UHMWPE, HDPE, LDPE, LLDPE and an ethyleneeoctene copolymer (Engage) were e-beam irradiated to 30 or 60 kGy in vacuum or in air and stored at room temperature in air. EPR spectroscopy was used to investigate macro-radicals produced during irradiation and their post-irradiation changes. FTIR spectroscopy was used to monitor changes in the polymer structure, induced by irradiation, and to follow post-irradiation oxidation. We found that the crystallinity and the size of the crystalline lamellae, in particular, play a major role on the post-irradiation effects. The low-crystallinity polyethylenes showed no oxidation or oxidation only to a small extent, even when irradiated and stored in air. On the contrary, development of postirradiation oxidation was observed in HDPE and UHMWPE. We attribute these results to a different reactivity of the macro-alkyl radicals formed upon irradiation in the amorphous or in the crystalline phase. While the radicals formed in the amorphous phase decay in short time, the migration time of the radicals trapped in the crystalline phase to the amorphous one is a key factor, governing the oxidation process.
| Titolo: | Post-irradiation oxidation of different polyethylenes | |
| Autori Riconosciuti: | ||
| Autori: | Ilenia Carpentieri; Valentina Brunella; Pierangiola Bracco; Maria Cristina Paganini; Elena Maria Brach del Prever; Maria Paola Luda; Sara Bonomi; Luigi Costa | |
| Data di pubblicazione: | 2011 | |
| Abstract: | The radiation-induced oxidative degradation of polyethylenes (PEs) with different degrees of crystallinity was characterized after electron-beam irradiation and during storage at room temperature. UHMWPE, HDPE, LDPE, LLDPE and an ethyleneeoctene copolymer (Engage) were e-beam irradiated to 30 or 60 kGy in vacuum or in air and stored at room temperature in air. EPR spectroscopy was used to investigate macro-radicals produced during irradiation and their post-irradiation changes. FTIR spectroscopy was used to monitor changes in the polymer structure, induced by irradiation, and to follow post-irradiation oxidation. We found that the crystallinity and the size of the crystalline lamellae, in particular, play a major role on the post-irradiation effects. The low-crystallinity polyethylenes showed no oxidation or oxidation only to a small extent, even when irradiated and stored in air. On the contrary, development of postirradiation oxidation was observed in HDPE and UHMWPE. We attribute these results to a different reactivity of the macro-alkyl radicals formed upon irradiation in the amorphous or in the crystalline phase. While the radicals formed in the amorphous phase decay in short time, the migration time of the radicals trapped in the crystalline phase to the amorphous one is a key factor, governing the oxidation process. | |
| Volume: | 96 | |
| Fascicolo: | 4 | |
| Pagina iniziale: | 624 | |
| Pagina finale: | 629 | |
| Digital Object Identifier (DOI): | 10.1016/j.polymdegradstab.2010.12.014 | |
| Parole Chiave: | Oxidation; e-Beam irradiation; Polyethylene; Radicals | |
| Rivista: | POLYMER DEGRADATION AND STABILITY | |
| Appare nelle tipologie: | 03A-Articolo su Rivista |
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http://hdl.handle.net/2318/85064
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