Increasing the stream of recycled plastic necessitates an approach beyond the traditional recycling via melting and re‐extrusion. Various chemical recycling processes have great potential to enhance recycling rates. In this Review, a summary of the various chemical recycling routes and assessment via life‐cycle analysis is complemented by an extensive list of processes developed by companies active in chemical recycling. We show that each of the currently available processes is applicable for specific plastic waste streams. Thus, only a combination of different technologies can address the plastic waste problem. Research should focus on more realistic, more contaminated and mixed waste streams, while collection and sorting infrastructure will need to be improved, that is, by stricter regulation. This Review aims to inspire both science and innovation for the production of higher value and quality products from plastic recycling suitable for reuse or valorization to create the necessary economic and environmental push for a circular economy.
Increasing the stream of recycled plastic necessitates an approach beyond the traditional recycling via melting and re‐extrusion. Various chemical recycling processes have great potential to enhance recycling rates. In this Review, a summary of the various chemical recycling routes and assessment via life‐cycle analysis is complemented by an extensive list of processes developed by companies active in chemical recycling. We show that each of the currently available processes is applicable for specific plastic waste streams. Thus, only a combination of different technologies can address the plastic waste problem. Research should focus on more realistic, more contaminated and mixed waste streams, while collection and sorting infrastructure will need to be improved, that is, by stricter regulation. This Review aims to inspire both science and innovation for the production of higher value and quality products from plastic recycling suitable for reuse or valorization to create the necessary economic and environmental push for a circular economy.
“…Then, the capsules were heated twice from the ambient temperature and up to 300°C with a heating rate of 10°C/min. The capsules were cooled at the same rate while the results were reported from the second cycle [10] The crystallization index of the polymer can be calculated from the equation number (1)…”
The properties of these polymers, as in the case of any materials, depending on the molecular weight of the polymer and the structure of the polymer chains. The main objective of this work is to study the mechanical and physical properties of pure PP and HDPE. To obtain a full characterization of pure polymer, samples were produced using a compression molding technique. Polymeric samples successfully filled the cavity of the die. The mechanical properties of PP and HDPE were determined using three-point bending, compression, hardness and impact test. While the physical properties were studied through density and water absorption. Also, the thermal analysis behavior was determined by thermogravimetric analysis, differential scanning calorimetry and thermomechnical analysis. Results showed the structure affects the properties. The PP showed better elastic modulus and strength due to the methyl attached to the carbon that prevents the chain rotation and hence makes the material stronger but inflexible. On the other hand, the absorbed energy of PP is less than that of HDPE. The thermogravimetric analysis results show a single weight-loss event with a degradation temperature of 310°C for HDPE and 255°C for PP. The differential scanning calorimetry shows that the crystallinity of PP (≅51) is less than that for HDPE (≅68) due to the difference in the specific heat. The coefficient of thermal expansion of HDPE is higher than that of PP due to the stronger interatomic forces.
Das Vergrößern des Recyclingstroms erfordert einen neuen Ansatz, der über das Schmelzen und Umformen hinausgeht. Es gibt einige Techniken des chemischen Recyclings mit dem Potential, bestehende Recyclingmöglichkeiten zu ergänzen. In diesem Aufsatz sind die Methoden des chemischen Recyclings dargestellt und anhand einer Ökobilanz bewertet, ergänzt durch eine Aufzählung von Prozessen und Firmen in diesem Bereich. Wir zeigen, dass bestimmte Techniken besonders für spezifische Müllströme geeignet sind und dass nur eine Kombination aus den vorhandenen Methoden geeignet ist, das Kunststoffmüllproblem zu lösen. Aktuelle Forschung sollte realistischeren und weniger reinen Mischströmen größere Aufmerksamkeit widmen, während Trenn‐ und Sortierprozesse z. B. durch effektivere Regularien verbessert werden müssen. Dieser Aufsatz soll zur Entwicklung von Verfahren inspirieren, mit denen hochwertige Produkte hergestellt werden können, die die Kreislaufwirtschaft antreiben, indem sie nötige Wirtschaftsanreize und Erleichterungen für die Umwelt bieten.
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