32〜37年間生物活性な土壌中に埋没していたLDPEの酸化劣化と分子量変化

概要

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The degradation of the thick parts of a LDPE container which was confirmed to have been buried under bioactive soil for 32-37 years was investigated by the molecular weight measurements and reflectance FT-IR spectroscopy of the surface. The depth profile of the degradation state was also investigated. The number averaged molecular weight of PE just under the surface was about one half of that of the internal part. This is the first case where the decrease of the molecular weight of the LDPE was directly observed under the oxidation promoted by the bioactive circumstance. The surface FT-IR spectra demonstrated the presence of carbon-carbon double bonds which are characteristic of the LDPE degraded under bioactive condition. The depth profile of microscopic FT-IR and the distribution of oxygen atoms observed by EPMA line analyses showed that the oxidation extended to as far as 40μm depth from the surface. These results suggested that even the high molecular weight LDPE could biodegrade as opposed to the generally accepted opinion.
日本ゴム協会の論文