[M-IS19] 地球科学としての海洋プラスチック

[MIS19-06] ポリオレフィン系マイクロプラスチックの構造と物性

★招待講演

*高原 淳¹、梶原 朋子¹、An Yingjun¹、Padermshoke Adchara¹、陣内 浩司²、佐々木 園³、磯辺 篤彦¹ (1.九州大学、2.東北大学、3.京都工芸繊維大学)

キーワード：マイクロプラスチック、ポリオレフィン、環境劣化、精密特性解析

Plastic products, particularly polyethylene (PE) and polypropylene (PP) have been widely used daily necessities for about 50 years. These products are indispensable not only for daily convenience but also for medical necessity. On the other hand, plastics pollution of the oceans, rivers, and soil has become a serious issue in recent years. Especially, plastic wastes with size of 5 mm or less are called microplastics (MPs). In this talk, structure and physicochemical properties of microplastics collected from the surface layer in the sea near Japan were characterized. The target sample size in this study is on the order of mm which was collected by Neuston net and can be observed with the naked eye. Since MPs were floated on the surface of the sea, collected MPs were mainly composed of PP, PE and foamed polystyrene (PS) which density were lower than sea water. Polymer components in MPs were characterized by polarizing optical microscopy (POM), transmission electron microscopy (TEM), RAMAN scattering, infrared (IR) spectroscopy and wide-angle X-ray diffraction (WAXD). MPs which showed birefringence were crystalline polyolefin and without birefringence was mainly foamed PS. Cross sectional TEM observation of MP which was identified as PP revealed the presence of degraded amorphous phase on the surface. WAXD results revealed that the polyolefin film or plate was fragmented while maintaining the orientation state of the crystallite in the film to some extent. IR microscopic measurement of cross section of polyolefin MP clarified that oxidation was proceeded from the surface. In addition, the results of nanoindentation of MP which was identified as PP, it was revealed that the surface of MP became brittle due to photo-oxidative degradation. Furthermore, this presentation contains focuses on the mechanism of MP formation by evaluating the structure and physical properties of fragments generated by mechanically stimulating PP after artificial weathering.