| POLYMERS Vol.69 No.11 |
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COVER STORY
Recycle: Responsible Consumption and Production |
| COVER STORY: Highlight Reviews |
| Recycling of Waste Plastics Using Sub- and Supercritical Fluids | Takeshi SAKO, Idzumi OKAJIMA |
| <Abstract> Plastics are indispensable materials in our daily life and large amounts of waste plastics is incinerated or buried in the ground. How to reuse waste plastics is an important issue. In this review, the feedstock recycling of waste plastics using a subcritical or supercritical fluid as a decomposition solvent is introduced, where a subcritical or supercritical fluid is a high temperature and high pressure fluid and has a large decomposition power for organic materials. In case of the waste plastic recycling, a subcritical/supercritical water or alcohol is used in many cases. The following topics are explained: [1] monomerization of polyethylene terephthalate with subcritical water or subcritical/supercritical ethylene glycol, [2] monomerization of nylon 6 or aromatic polyamide with subcritical water, and [3] decomposition of thermosetting epoxy resin in carbon fiber reinforced plastics and recovery of carbon fiber sheets with supercritical alcohol or supercritical acetone. Keywords: Supercritical Fluids / Subcritical Fluids / Waste Plastics / Monomerization / Decomposition / PET / Polyamide / CFRP |
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| Recycling of Polyvinyl Chloride using Dechlorination | Toshiaki YOSHIOKA, Shogo KUMAGAI, Yuko SAITO |
| <Abstract> Regarding the dificulty and recycle polyvinyl chloride (PVC), we introduced the effective utilization of dechlorination. In particular, the possibility of PVC recycling was shown through the technological concept and upgrading to apply and circulate it in the processes of upstream industries by removing chlorine, and the utilization for other waste treatment. Keywords: PVC / Chlorine Circulation / Dechlorination / Chemical Recycling |
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| COVER STORY: Topics and Products |
| Self-Resilience Ability of Polymers and Advanced Mechanical Recycling | Shigeru YAO, Patchiya PHANTHONG |
| <Abstract> Recently, the load of plastics on the environment has become a big problem. Mechanical recycling is drawing attention as a means for solving this problem, however it has been considered that there is no effective means for solving the deterioration of physical properties. In this paper, we introduce the advanced material recycling process that enables us to improve the physical properties by utilizing the self-resilience ability of polymers that we recently found. Keywords: Self-Resilience Ability / Mechanical Recycle / Physical Degradation / Physical Regeneration / Extruder |
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| New Devulcanization Methods for Tire Rubber | Masahiro HOJO, Hideyuki TAGAYA |
| <Abstract> We have developed a new tire rubber devulcanization method toward the realization of a Circular Economy. This devulcanization method makes it possible to obtain a recycled rubber having a higher molecular weight than ever before, without using any special chemicals other than the organic solvent. In particular, it was confirmed that the decrosslinking reaction proceeds efficiently while maintaining the polymer molecular weight in a specific fatty alcohol under an air atmosphere at 200℃. Keywords: Circular Economy / Devulcanization / Fatty Alcohol |
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| Acceleration of Enzymatic PET Hydrolysis by the Addition of Surfactants | Norifumi KAWAKAMI, Kenji MIYAMOTO |
| <Abstract> Poly（ethylene terephthalate） （PET） is a synthetic polymer with high stability and transparency, useful for various purposes, resulting in a wide spread of PET-based commercial products in society. The efficient degradation of PET is thus important for implementing a sustainable society. Enzymatic degradation of PET is one of the most prominent approaches for this purpose. We have recently found that enzymatic PET hydrolysis can be accelerated by non-covalent modification of PET surfaces using alkyl surfactants such as sodium dodecyl sulfate. Specifically, the surfactants were incubated with PET prior to the addition of enzymes. As a result, the catalytic activity of PETase, a PET specific hydrolase, was improved 120-fold compared with the reaction in the absence of surfactants. The possible interpretation of this acceleration effect was that the surfactant mediated the interaction between hydrophilic enzymes and hydrophobic PET substrate. Therefore, if we could design the surfactant molecule more efficiently enhancing the interactions, the PET hydrolysis would be further accelerated. Keywords: PET / PET Hydrolase / Surfactants / PETase |
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| A Solvent-based Method to Purify Recycled PP | John M. LAYMAN, Dimitris I. COLLIAS |
| <Abstract> Solvent-based purification processes provide a non-chemical, lower-energy pathway to recycle waste plastics. The process shared in this article is based on the use of a hydrocarbon solvent at elevated temperature and pressure, and a novel combination of standard chemical engineering unit operations, such as liquid – liquid extraction, sedimentation, size exclusion and adsorbent filtrations, and devolatilization. These processes purify the recycled plastic via removal of odor, volatile organic chemicals, and other organic and particulate contaminants and additives. The initial focus of this technology is on polypropylene （PP）； however, purifications of other polymers are also possible. Keywords: Solvent-Based Recycling / Sustainability / Plastics Recycling / Circular Economy / Polypropylene |
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| Polymer Science and I: A Personal Account |
| Incredible Power | Kai KAN |
| <Abstract> I experienced “incredible power” throughout my research life. This power was a fortunate power, that gave me happiness from failure to succeed in my direction of research. I would like to explain this “incredible power” in two awesome research experiences in my heartfelt emotion. |
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| Front-Line Polymer Science |
| Role of Polymers in a Sustainable Society: Current Situation of Fiber Reinforced Plastics Recycling | Tohru KAMO |
| <Abstract> The market size of fiber reinforced plastics (FRP) is expected to expand significantly in near future owing to their distinguished mechanical properties as a material. However, FRP is one of the most difficult plastics for recycling and the majority of the waste FRP is currently deposited in land fills. In the recycling of printed circuit boards (PCB), increasing value of the liquid product derived from pyrolysis of the PCB by debromination is required. And in the recycling of carbon fiber reinforced plastics (CFRP), the development technology for recovering carbon fibers with minimal degradation of their physical properties is important. In this article, the latest research works using pyrolysis, solvolysis, and super critical solvents for recycling of PCB and CFRP are introduced. To ensure the continued use of FRP, it is important not only to develop recycling technologies, but also to reduce the environmental load of the entire life cycle of the materials, including production, use, recovery and recycling. Keywords: Recycle / CFRP / Carbon Fiber / Wast Plastics / Epoxy Resin / Pyrolysis / Solbolysis / Super Critical Solvent |
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