| POLYMERS Vol.70 No.1 |
| >> Japanese | >> English |
COVER STORY
Polymers in the Marine Environment |
| COVER STORY: Highlight Reviews |
| Oceanic Pollution Caused by Microplastics | Atsuhiko ISOBE |
| <Abstract> Current abundance, prediction in the future, and environmental influences of pelagic microplastics in the ocean are descrived on the basis of accomplishments by ocean science and related reseach fields to date. Also suggested is possible collaborations between ocean and polymer sciences. Keywords: Ocean Plastics / Microplastics |
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| Importance of Fundamental Polymer Science of Microplastics | Atsushi TAKAHARA |
| <Abstract> As the amount of polymer consumption increased, microplastics (MPs) generated from disposed polymer products are flowing into the environment and becoming a serious social problem. In this review, analytical methods on MP collected in the ocean and a model experiment of an MP formation process are introduced. Also, the author emphasizes that the basic research is indispensable for solving the MP issue. Keywords: Microplastic / Polyolefin / Degradation / Photooxidation / Fragmentation / Analytical Methods/ Separation |
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| Microplastics and Polymer Recycle | Isaburo FUKAWA, Youichiro IDE |
| <Abstract> An outline of marine plastic litter and microplastic problems is summarized. In addition, the transition to the circular economy (resource recycling), that is, the state of promotion of mechanical recycling and various chemical recycling of single-use plastics made of PET, PE, PP, (foamed) PS, is summarized in the EU and Japan. PE film (MW110,000) diminishes to a molecular weight of 20,000 or less when exposed to sunlight for 1 year, becoming brittle to and able to form microplastics. Moreover, it was found by computer simulation that 33 to 45 years of sunlight exposure is required to obtain PE with a molecular weight of 500, which has been confirmed to be biodegradable. This article also introduces and explains Japan’s polyolefin recycling project. Contrary to expectations, the chemical degradation of the recycled plastics from post consumer recyclates (PCR) was not observed with SEC and IR analysis. A toiletry bottle was successfully prototyped using recycled PE from the PCR, and its mechanical properties were equivalent to that of a virgin bottle. Keywords: Ocean Plastics / Microplastics / Circular Economy / Mechanical Recycle / Chemical Recycle / Single Use Plastics / PE / PP |
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| COVER STORY: Topics and Products |
| A Puzzle of Lost Marine Microplastic: Fragmentation Mechanism of Polypropylene in Water | Hisayuki NAKATANI |
| <Abstract> A polypropylene (PP) film photodegradation test was performed in water with a specific photocatalyst under visible light irradiation to identify its fragmentation mechanism. The results showed that the surface exfoliation was provoked by the test. The spherulite structure contributed to the surface microcrack location and growth. The microcrack allowed entrance of water into the inner amorphous part. The water caused an internal stress by expanding itself due to radiant heat from the visible light irradiation and induced a microcraze in the interlamellar amorphous region. The microcraze developed into an internal microcrack, and surface microcracks finally coalesced together, producing a planar exfoliation. The weight change ratio and rate of the photodegraded PP film showed multi-stages with the increase of photodegradation time. The increment of positive rate was small, showing that the exfoliation caused suppression of the autoxidation rate. The negative rate was due to the exfoliation behavior and was nonlinear to the photodegradation time. Keywords: Microplastics / Polypropylene / Photodegradation / Surface Exfoliation / Water |
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| Design and Synthesis of Novel Biodegradable Copolymers with Controlled Sequence | Yuushou NAKAYAMA |
| <Abstract> Poly(glycolic acid) (PGA), poly(L-lactide) (PLA) and polyamide 4 (PA4) have been known for their biodegradability. We developed a series of novel sequential copolyesters and copoly(ester amide)s containing the repeating units of common polyesters such as poly(ethylene terephthalate) (PET) as well as those of PGA, PLA or PA4 as new biodegradable polymers. The 2 : 1 condensation products of hydroxy acids (L-lactic acid or glycolic acid) and ethylene glycol were polymerized with terephthaloyl chloride to produce novel sequential polyesters, poly(GEGT) and poly(LELT), respectively. Poly(GEGT) showed relatively high melting temperature (Tm) while poly(LELT) was amorphous. Poly(GEGT) exhibited high biodegradability in seawater. We also synthesized a series of new sequential copoly(ester amide)s containing γ-aminobutyric acid (GABA) units. The copoly(ester amide)s showed higher thermal stability and lower Tm than those of PA4, indicating their improved processability. The copoly(ester amide)s also exhibited biodegradabiity in seawater depending on their structure. Keywords: Sequential Copolymer / Copolyesters / Copoly(ester amide)s / Glyclic Acid / Lactic Acid / γ-Aminobutyric Acid / Diol / Dicarboxylic Acid |
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| The Naturally Occuring Polymer PHBH and its Realisation | Shunsuke SATO |
| <Abstract> We have been developing “KANEKA Biodegrable Poymer PHBH®” as an environmentally compatible material with technical integration of fermentation, downstream process and polymer processing technology. PHBH consists of 3-hydroxybutyrate and 3-hydroxyhexanoate(3HHx) and is a naturally occuring biopolymer synthesized by a bacterium as an energy and carbon storage material. Thus, PHBH has exellent biodegradability in various environments including the ocean. So, we believe that PHBH could be one of the solutions for the current marine pollution problem. To realise PHBH, it is highly important to regulate the fractions of 3HHx since the material and mechanical properties of the PHBH depend on the fractions of 3HHx. Therefore, we examined the precise control of the 3HHx fractions by fine-tuning the expressions of phaJ, the genes encoding enoyl-CoA hydratases, which are responsible in the intracellular supply of 3HHx and by regulating the reactivity of the PHBH polymerizing enzyme (PhaC) against 3HHx. To make plastics a truly environmentally friendly material, it will be important for manufactures and users to be smarter. Keywords: PHBH / Naturally Occurring Polymer / Biodegradable / Marine Pollution |
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| Polymer Science and I: A Personal Account |
| What's Your Strength ? | Shinji KANEHASHI |
| <Abstract> This personal essay is written by Dr. Shinji Kanehashi. I talk about my career and the key points that influenced my thoughts as an independent researcher. |
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| Front-Line Polymer Science |
| Recent Development in the High-Performance of Biodegradable Biomass Plastics | Tadahisa IWATA |
| <Abstract> To establish a sustainable material production system and preserve the beautiful global environment forever, it is desirable to develop “biomass plastics” that are made from renewable biomass instead of petroleum, and “biodegradable plastics” that are completely degraded into carbon dioxide and water by enzymes secreted by microorganisms in the environment. This front-line describes recent development in the high-performance biodegradable biomass plastics. In particular, some important and interesting researches will be presented, focusing on biodegradable initiation functions and marine biodegradability. Keywords: Biodegradable Biomass Plastics / Biodegradable Plastics / Marine Biodegradation / Biodegradable Initiation Function / BOD-Biodegradation / Enzymatic Degradation / Deepsea Biodegradation |
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| Polymer Select |
| Elucidation of the Characteristics of Hierarchical Structures of the Solid State of Polymers | Kohji TASHIRO |
| <Abstract> In order to elucidate the detailed characteristics of the hierarchical structure of crystalline polymer solids, a systematic research has been conducted by studying their formation process and their relation to the physical properties of polymers. In these researches, such a wide variety of methods have been utilized as wide-angle/small-angle X-ray scattering, neutron scattering, electron diffraction, infrared and Raman spectroscopy, and computer simulations containing lattice dynamics, molecular dynamics and density functional theory. Some concrete results are described in detail and the future of structural science of polymer solids has been discussed. Keywords: Polymer Solid / Hierarchical Structure / Structural Evolution Process / X-ray Scattering / Neutron Scattering / Electron Diffraction / Vibrational Spectroscopy / Computer Simulation |
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