The mechanical and thermal properties of injection-molded recycled polyethylene were studied, specifically with respect to the influence of large-scale washing and melt-compounding of polyethylene from post-consumer packaging waste. Three types of materials were studied: those taken after sorting, after sorting and washing, and after sorting, washing, and melt-compounding, including melt-filtration, all from a large-scale material flow. The materials were further processed on a laboratory scale and compared. The results showed that large-scale washing significantly reduced thermo-oxidative stability, as well as molar mass and melt viscosity. The degradation during large-scale washing made the material susceptible to further degradation in the subsequent extrusion compounding, as shown by the differences in compounding at 240 and 200 °C using a high-shear screw configuration. The compounding parameters, screw configuration, and compounding temperature did not influence the stiffness and strength of the unwashed and large-scale-washed materials, but the elongation-at-break varied, specifically, with the increased temperature. Washing had an influence on the mechanical properties as well, and the unwashed material provided molded samples with stiffness measurements of approximately 550 MPa, whereas the large-scale-washed material provided stiffness of approximately 400 MPa. The strength measurements were approximately 15 MPa for samples made of both unwashed and large-scale-washed material, and the elongation-at-break measurements were between 50 and 150%. The large-scale-washed and compounded materials had very different mechanical properties, with stiffness measurements of approximately 320 MPa, strength of approximately 20 MPA, and elongation-at-break of approximately 350%. The significantly different mechanical properties of the large-scale-washed and compounded materials were likely due to the melt-filtration included in the compounding through the removal of metal and rubber particles, and they may also have been due to the compatibilizing and stabilizing additive used in the compounding. © 2022 by the authors.
Swedish recycling businesses argue that the Non-Toxic Environmental target gets too much weight and that resource efficiency gets too little focus, which results in decreased recycling. The purpose of this paper is to highlight different factors that recycling of waste decisions should consider, as well as contributing to a constructive discussion of the overall principles and policies for recycling. How recycling works in practice is explored based on nine interviews with stakeholders from the governmental agency level to recycling businesses. Theory with regards to ethics, risk, decision-making, governmental policy and laws is summarised. Finally, the discrepancy and connection between practice and theory is analysed. If recycling of waste is seen as a decision problem, the choice is between to recycle (in different ways) or not to recycle (i.e., energy recovery and/or landfill). Based on risk and decision theory, all relevant goals should be considered. This requires a broader problem framing when goals are in conflict. All parties agree that recycled and virgin material should be treated equally. From a higher policy perspective, it should then be demonstrated that any use of material (recycled and/or virgin) minimize environmental impact and promotes long-term sustainability. © 2020 by the authors.
The manufacturing industry in the Nordic countries aims to include closing product and material loops to recover values in their circular economy strategies. Recirculating strategies for products and materials are required for existing products that are part of the stock and are also anticipated to be aligned with products designed for circularity and circular business models in the future. Options to capture value of discarded products are diverse and include reuse, remanufacturing and material recycling. The Circular Economy Integration in the Nordic Industry for enhanced sustain-ability and competitiveness (CIRCit) project developed a framework to guide decision makers in the industry on how to identify suitable treatments and subsequent use at the end of use or end of life of a product and how to select among different options. Factors considered in the assessment include technical feasibility, necessary efforts, networks of business partners, legal implications and overall sustainability aspects. Our empirical studies show great support for decision-makers in the value recovery of different products with different complexity levels. It is also concluded that the properties of products at their end of use are the main drivers behind selecting a proper recirculation strategy. This study contributes with an empirical evaluation and a consistent terminology framework for recirculation options. The general setup is relevant for the Nordic countries. © 2021 by the authors.
The substitution of mineral aggregates with crumb rubber (CR) from waste end‐of‐life tires (ELTs) in the asphalt concretes, has been considered a sustainable paving industry approach. The rubber has been used to construct pavements with proven enhanced resilience and improved durability. However, some issues related to the rubber’s surface adhesion or swelling may arise with these practices and generate complications (binder consumption, temperatures, mixing times). One possible solution to overcome the materials’ compatibility problems is to pre‐treat the CR’s surface before its incorporation into the asphalt mixes to allow a surface functionalization that can enhance coverage and cohesion inside the mixes. The physical treatments using radiations‐based beam are already exploited in the plastic recycling industries avoiding the use of chemicals in con-siderable amounts. Such treatments permit the recovering of large quantities of polymer‐based materials and the enhancement of interfacial properties. This article provides an overview of existing surface treatments of polymers and especially rubber, including gamma ray, UV‐ozone, micro-waves, and plasma. Several studies have shown an overall improvement of the rubber surface’s reactive properties due to contaminant removal or roughness enhancement attributed to cross‐link-ing or scission reactions occurring on the rubber’s surface layer. With those properties, the asphalt mixes’ phase stability properties are increased when the pre‐treated rubber is incorporated. The treatments would permit to increase the CR quantities, yet reduce the layer stiffness, and improve the durability and the sustainability of future advanced road pavements. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
The fashion industry is becoming one of the largest emitters worldwide due to its high consumption of raw materials, its effluents, and the fact that every garment will eventually contribute to the vast amount of waste being incinerated or accumulating in landfills. Although fiber-to-fiber recycling processes are being developed, the mechanical properties of the textile fibers are typically degraded with each such recycle. Thus, tertiary recycling alternatives where textiles are depolymerized to convert them into valuable products are needed to provide end-of-life alternatives and to achieve circularity in the fashion industry. We have developed a method whereby cotton waste textiles are depolymerized to form a glucose solution, using sulfuric acid as the sole catalyst, with a high yield (>70%). The glucose solution produced in this process has a high concentration (>100 g/L), which reduces the purification cost and makes the process industrially relevant. This method can be applied regardless of the quality of the fibers and could therefore process other cellulosic fibers such as viscose. The glucose produced could subsequently be fermented into butanediol or caprolactam, precursors for the production of synthetic textile fibers, thus retaining the value of the waste textiles within the textile value chain. © 2022 by the authors.