Mixed Plastic Waste Research Articles

Upgrading Mixed Plastic Waste through Industrial Symbiosis: Pseudoductile Regenerated Cellulose Fiber-Reinforced Shredder Residue Composites

Upgrading Mixed Plastic Waste through Industrial Symbiosis: Pseudoductile Regenerated Cellulose Fiber-Reinforced Shredder Residue Composites

Integrated Ziegler-Natta/Brookhart-Ni Catalysts for the Synthesis of Sutured Polar High-Impact Polypropylenes.

The direct synthesis of polar high-impact polypropylenes using industrially-preferred heterogeneous catalysts is challenging due to the poisoning of polar functional groups towards metal center and the high stereo-selectivity requirement. In this work, dual-site catalysts combining Ziegler-Natta and Brookhart-Ni catalysts were used to produce polar polyolefin ionomers, followed by polar high-impact polypropylenes containing isotactic polypropylene and branched polyethylene as toughening agents. Three combination modes between these catalysts were investigated, including mixed, core-shell, and integrated types. The integrated dual-site catalyst achieved the optimal material properties because the polyolefin ionomer acted as a suture molecule that stitched different components into a whole network. This produced sutured polar high-impact polypropylenes with excellent mechanical properties and compatibility with polar substances. The restraining effect of the suture molecules greatly reduced the release of microplastic particles after aging. Moreover, the obtained polar high-impact polypropylene can serve as an efficient compatibilizer to recycle polyethylene/polypropylene mixed-waste plastics. This work provides an appealing and potentially practical strategy to upgrade the widely used polypropylenes and to alleviate the ever-growing plastic pollution issue.

Catalytic Conversion of Plastic Waste into Diesel Fuel through Pyrolysis and Hydroprocessing

This study evaluates the potential of hydro-processed plastic pyrolysis oil (HPO) as a sustainable alternative fuel derived from mixed plastic waste. The physicochemical properties of diesel, mixed plastic pyrolysis oil (MPPO), and HPO were thoroughly analyzed according to IS standards, enabling a direct comparison and alignment of HPO characteristics with EN590 diesel fuel standards. Gas chromatography-mass spectrometry (GC-MS) analysis identified key fuel components—n-alkanes, alkenes, benzene, and naphthalene with HPO showing 98% compositional similarity to commercial diesel. The HPO blend with various percentage of pure diesel ratio is (30:70, 60:40 and 90:10). The hydroprocessing technique effectively reduced the alkene content of MPPO, enhancing the purity and quality of the resulting HPO. This refinement was crucial in ensuring that the oil met the necessary fuel standards. Engine performance evaluations further indicated that blending HPO with conventional diesel resulted in emissions with 95% similarity to those of standard diesel fuel. This close match in emission profiles underscores the potential of HPO as a cleaner and more environmentally friendly fuel alternative. Additionally, the increased aromatic content in HPO, due to hydroprocessing, significantly improved combustion properties. This enhancement not only supports the feasibility of using HPO as a substitute for traditional diesel but also suggests that HPO may offer superior performance in specific applications. Overall, these findings highlight the potential of HPO as a sustainable fuel option, capable of addressing the environmental impacts associated with both plastic waste and fossil fuel consumption. The study demonstrates the environmental benefits of converting plastic waste into valuable fuel through pyrolysis and hydroprocessing, offering a promising strategy for sustainable plastic waste management and advancements in environmental sustainability and the fuel industry.

Combined thermochemical-biotechnological approach for the valorization of polyolefins into polyhydroxyalkanoates: Development of an integrated bioconversion process by microbial consortia

Waste management of persistent polymers such as polyolefins (PO)1 still represents a major challenge, often leading to material loss from the value chain and contributing to plastic pollution. This study investigated an integrated process to valorize PO pyrolysis side stream. PO wax was recovered and used as a feedstock for a microbial bioconversion process. A modified emulsification protocol (using two-surfactants system) allowed the successful dispersion and bioconversion of PO wax without the need of the extra oxidation step. Enrichment of plastic landfill inocula allowed to develop efficient mixed microbial consortia (MMC) able to grow on PO wax. Adaptive laboratory evolution improved 4 times cell growth, leading to 2.6–17.3 times shorter lag phase. The bioconversion process using the adapted MMC was performed in a 2 L-bioreactor with PO wax-emulsified media (10 g L−1) at neutral pH and 20% pO2. 87% of substrate was consumed within 12 h and complete consumption was achieved within 48 h (4 times faster than previously reported). A maximum of 2.95 gCDW L−1of biomass was produced, while the intracellular triglycerides reached a maximum of 105.5 mg L−1 at 30 h. Moreover, the conversion of PO wax into polyhydroxyalkanoates (PHAs) was demonstrated and the production was maximized by statistical optimization. Maximum PHA titer of 384 0.1 mg L−1 was achieved, which represents a 1.5–17 times improvement from previous reports. This integrated thermochemical-biotechnological approach might represent an interesting strategy to valorize and upcycle currently unrecyclable PO-rich mixed plastic waste streams, thus improving the circularity of the plastic sector.

Environmental and economic assessment of mixed plastic waste pelletization in the Gulf Cooperation Council region

Pelletizing mixed plastic wastes (MPW) has gained interest as an upcycling technology and an alternative to conventional recycling. To investigate its potential, we conducted a cost analysis and life-cycle assessment (LCA) for a conceptual pelletization facility designed to produce 1 kg of pellets per batch of MPW (comprising polyethylene—PE and polypropylene—PP). This work has the following merits: (i) evaluating environmental impact (EI), cost analysis, and mechanical strength based on actual experimental data and its comparison with local and international manufacturers; (ii) enabling the evaluation of LCA impacts of MPW pellets; and (iii) emphasizing the significance of waste management in reducing EIs. The following ten EIs were assessed: climate change (CC), net energy, particulate matter formation, natural land transformation, metal depletion, marine ecotoxicity, ionising radiation, freshwater ecotoxicity, freshwater eutrophication, and terrestrial ecotoxicity. The CC of the as-synthesized pellets is 1.26 kg CO2 eq., significantly lower than the data obtained from the Gulf Petrochemicals and Chemicals Association (GPCA) and an actual plant in Gulf Cooperation Council (GCC) countries. Additionally, the net energy required for the production of 1 kg of pellets is 54.1 MJ, while the cost is around 0.55 USD. The tensile strength of MPW pellets (24.63 MPa) falls between that of PE virgin pellets (21.12 MPa) and PP virgin pellets (28.12 MPa). This suggests that the MPW pellets exhibit competitive strength characteristics, warranting its consideration for applications where moderate strength is required. Overall, the competitive cost, coupled with the reduced EIs, demonstrates the potential of pelletization as a sustainable and economically viable waste management solution.

Photooxidation of Polyolefins to Produce Materials with In-chain Ketones and Improved Materials Properties.

Herein, we report a selective photooxidation of commodity postconsumer polyolefins to produce polymers with in-chain ketones. The reaction does not involve the use of catalyst, metals, or expensive oxidants, and selectively introduces ketone functional groups. Under mild and operationally simple conditions, yields up to 1.23 mol% of in-chain ketones were achieved. Installation of in-chain ketones resulted in materials with improved adhesion of the materials and miscibility of mixed plastics relative to the unfunctionalized plastics. The introduction of ketone groups into the polymer backbone allows these materials to react with diamines, forming dynamic covalent polyolefin networks. This strategy allows for the upcycling of mixed plastic waste into reprocessable materials with enhanced performance properties compared to polyolefin blends. Mechanistic studies support the involvement of photoexcited nitroaromatics in consecutive hydrogen and oxygen atom transfer reactions.

Applications of H2-Enriched syngas and slag products from plastic wastes via novel plasma dual-stage-arc pyrolysis

Sustainable plastic waste management in the prevailing ‘new-normal’ post-pandemic scenario calls for calorific waste plastic up-cycling into high-end product recovery pathways. The present work employed a novel dual-stage arc plasma pyrolysis reactor to recover syngas and slag products from mixed plastics and Low-Density Polyethylene and Polyethylene Terephthalate (LDPE-PET) plastic waste feeds. Syngas product yield decreased while the solid slag yield increased with rising arc current, attaining 75% and 25% for mixed plastic waste feed and 59% and 41% for LDPE-PET wastes, respectively, at 200A arc current. The resultant syngas composition showed 83% and 77% H2 while 1.7% and 2.7% CO for mixed plastic waste-feed and LDPE-PET wastes, respectively, with no significant presence of CO2. Slag characterization studies revealed the presence of scattered pores on the slag surface, graphitic nanostructures due to scraped carbon depositions from electrode tips and the absence of aromatic groups due to complete conversion. High carbon content was observed in the slag due to the dissociation of lighter hydrocarbon and carbon dioxide on dual-arc exposure in two stages, underscoring the higher efficiency. For holistic integrated circular onsite ‘plastic waste-to-resource’ recovery-cum-application, electricity was generated from the resultant syngas and the slag was used for the manufacture of tiles in the community platform. Techno-economic evaluation of an up-scaled plasma pyrolysis facility shows the power recovery of 3.5 kWh/kg of waste plastic, with a net annual profit of $2800 and a payback period of 1.7 years. The findings of the present work suggest that the proposed integrated dual-arc plasma pyrolysis based plastic waste-to-resource recovery in circular-economy model has a viable outcome.

Co-pyrolysis of furniture wood with mixed plastics and waste tyres: assessment of synergistic effect on biofuel yield and product characterization under different blend ratio

Pyrolysis of waste furniture wood, mixed plastics and waste tyres was examined separately and in different combinations from the perspective of improved value products and energy production. The effect of different combinations of furniture wood, plastics and tyres on the product distribution during co-pyrolysis was analyzed. The experimental work throughout this study was performed at a temperature of 500 °C. Prior to the pyrolysis experiments, thermogravimetric analysis was done to assess the thermal degradation behavior of all selected feedstocks. During individual pyrolysis, mixed plastic wastes produced 70.6 wt% of pyrolysis liquid, which is 37.9% and 33.4% more than furniture wood and waste tyres. During co-pyrolysis, a binary blend of mixed plastics and waste tyres produced 63.3 wt% of pyrolysis liquid, which is 7.65% more than the logarithmic mean value, indicating a positive synergistic interaction on liquid production. The liquid yield of the ternary blend was observed to be as low as 54.4 wt% due to the lower volatiles present in the blend. The presence of volatiles in the feedstock is correlated with the production of liquids by individual and co-pyrolysis. For feed-flexible, more efficient, and cleaner operating systems, the increased liquid production offers crucial information. With the use of Fourier transform infrared spectroscopy (FT-IR) and gas chromatography/mass spectroscopy (GC–MS), the impact of different combinations on product characterization was investigated. The characterization study of the pyrolysis liquid obtained from mixed plastics showed the presence of different aromatic and aliphatic compounds. The findings offered viable options for efficiently utilizing waste materials, particularly plastics and tyres to improve the quality and substance of products.

A simulation-based techno-economic-safety-social-environmental decision-making framework for prioritizing plastic waste treatment processes

Chemical recycling technologies hold promising potential in converting mixed plastic waste into energy and chemicals. This study proposed a simulation-based quantitative life cycle sustainability assessment framework for the potential plastic waste valorization processes. Sustainability metrics including environment, economy, safety, society, and energy were quantified and comprehensively investigated. Based on the Bayesian best-worst weighting and vector-based ranking methods, the normalized and weighted life cycle sustainability scores were used to prioritize the best process. Gasification-based technology was found superior than incineration-based technology, especially in the economic, techno-energetic, and social aspects. However, incinerated-based process with direct CO2 emissions performed better in the environmental aspects compared with the process integrating with carbon capture and utilization unit. Additional environmental burdens were brought to the system when incorporating the carbon capture and methanol synthesis process. Increased system complexity might bring unexpected environmental burdens, and sometimes even outweighed the benefits. Various weights were assigned to the multi-criteria decision-making model, and the gasification-based process consistently ranked first across all scenarios.

Total separation of multi-plastic wastes using magnetic levitation with adjustable sensitivity

Novel separation method with high efficiency is of great significance for mechanical recycling mixed waste plastics plays. However, the efficiency of most extant methods is restricted by their shortage that the methods can only deal with binary mixtures. In this paper, a novel magnetic levitation (MagLev) separation method based on scaled-up MagLev device is proposed to handle multi-plastics. A theoretical model on distribution of magnetic flux intensity and levitation conditions is established to guide the design of separation process. Based on the theoretical analysis, different processes for separation of multi-plastics with different purpose can be realized. The high sensitivity allows the separation of plastics with similar appearances (e.g. transparent plastics like polycarbonate and polymethyl methacrylate) and densities (difference with 0.01 g/cm3). The adjustable distribution of magnetic field changes the levitation condition of the waste plastics. Thus, the sequential separation of multi-plastics and extraction of target material from multi-plastics mixture are successfully addressed. The experiments demonstrate that the purities of separated multiple plastics reach to approx. 100 %. Furthermore, additional advantages of low cost and no energy consumed in separation process make the method a promising solution for economically-viable and environmentally-friendly mass production procedure.

RECYCLING OF PLASTIC WASTE BY THE PYROLYSIS METHOD

Chemical recycling of plastic waste can be a useful complement to mechanical recycling to achieve the required rate of plastics recycling and create a climate-neutral and resource-saving circular economy. Various mixed plastic wastes to be recycled in the future are investigated under fully uniform intermediate pyrolysis conditions characterized by moderate heating rates and pyrolysis temperatures. The distribution of the product and the selected properties of the product are determined, and the mass and energy balance of the process is obtained. Product yield and composition are highly dependent on pyrolyzed residues. All results indicate that pyrolysis is a suitable process for obtaining chemical feedstocks from various complex mixed plastic wastes. The main mass and energy balances for chemical recycling of mixed plastic waste by pyrolysis method were determined. Products for recycling raw materials can be obtained from all investigated plastic waste. Product quality often depends on raw materials. The energy requirement for heating, melting, pyrolysis and evaporation is about 5% of the calorific value of the raw material. It has been demonstrated that 50 to 75% of the raw carbon can be recovered in the condensate and reintroduced into the value chain in the chemical industry.

An experimental investigation on performance, emission and combustion characteristics of IC engine using liquid fuel produced through catalytic co-pyrolysis of pressed oil cake and mixed plastics with the addition of nanoparticles

The study focuses on using a combination of diesel and a liquid fuel derived from the co-pyrolysis of pressed neem cake (PNC) and mixed waste plastics (MWP) containing waste polyethylene terephthalate (PET) and low density polyethylene (LDPE) in equal amounts with the help of cupric oxide (CuO) catalyst. The engine analysis was carried out using diesel and five different blends of co-pyrolysis oil with diesel in proportions of 20 % (20 % pyrolysis oil + 80 % diesel = PD20), 40 % (PD40), 50 % (PD50) and 100 % pyrolysis oil (PD100), respectively. Initially, the co-pyrolysis oil was produced using PNC and MWP in a ratio of 1:2 under different operating temperatures between 350 °C and 650 °C. The process temperature was optimized to yield maximum liquid oil, and the characterization study was performed. In addition to that, CeO2 nanoadditives were used to improve the properties of PD20 fuel. Different dosages of nanoadditives were blended with PD20 to prepare PD20@25 (PD20 + 25 ppm CeO2), PD20@50, PD20@75, and PD20@100. The objective of the study is to assess the performance, emission, and combustion characteristics of a diesel engine utilizing co-pyrolysis oil-diesel blend by including the nanoadditives. The analysis was carried out on a single-cylinder water-cooled diesel engine mounted with an eddy current dynamometer. The experiments demonstrated that the combination of PD20 and 50 ppm CeO2 resulted in a 6 % increase in thermal efficiency when compared to other blended fuels and diesel. When compared to all fuels, the PD20@50 produced a higher decrease in CO and HC emissions by roughly 30 and 6.2 %, respectively. The combustion analysis showed that the heat release rate (HRR) and maximum cylinder pressure were also found to have improved by adding nanoparticles.

High‐Performance Dynamic Photo‐Responsive Polymers With Superior Closed‐Loop Recyclability

AbstractChemical recycling to monomer (CRM) provides an ideal solution for reducing plastic waste and achieving a circular polymer economy. Cyclopentene (CP) and its derivatives are representative molecules that exemplify an efficient CRM process under mild conditions. However, most CP‐based polymers possess limited thermal and mechanical properties, constraining their potential applications. Herein, new CP‐based polymers with superior thermo‐mechanical properties and autonomous functions are proposed by integrating anthracene as a dynamic functional motif. Anthracenes not only serve as supramolecular cross‐linkages through strong π–π interactions but also form stronger chemical ones under UVA light irradiation, enhancing thermo‐mechanical properties. Furthermore, damage‐reporting, self‐healing, and local shape reprogramming capabilities are accomplished by utilizing the reversible nature of photodimerized anthracene. A mild and orthogonal depolymerization condition for the CP‐based polymers facilitates efficient monomer recovery even from mixed plastic wastes. This work presents a simple yet effective strategy to expand the usability of chemically recyclable polymers and contribute to a closed‐loop polymer economy.

Environmental impact of waste plastic oil and hydrogen-enriched diesel engines: A comprehensive review on performance, combustion, and emissions

This review focuses on the sustainable use of waste plastic by converting it into waste plastic oil (WPO) through catalytic pyrolysis. The primary objective is to explore the potential of WPO, derived from used polyethylene terephthalate bottles, as an alternative fuel for diesel engines. This review also evaluates WPO's physical and chemical properties, revealing that it possesses fuel attributes similar to those of petroleum-based fuels. Catalytic pyrolysis is employed on a laboratory scale, using catalysts such as silica, Zeolite Socony Mobil-5 (ZSM-5), alumina, and kaolin to extract WPO from mixed waste plastics. However, direct use of WPO in diesel engines has shown drawbacks, including significant combustion delays and increased emissions. To address these issues, this review suggests blending WPO with diesel fuel rather than using it as a standalone fuel. Furthermore, the review explores hydrogen enrichment in WPO blends to improve combustion efficiency. Hydrogen enrichment enhances thermal efficiency and reduces environmental emissions, showing potential for improved performance and lower brake-specific fuel consumption. This review presents a comparative analysis of various WPO blends with hydrogen enrichment, highlighting the benefits of incorporating hydrogen to boost combustion and performance. Although promising, further research is needed to ensure the sustainability and effectiveness of WPO blends as a long-term energy source.

Developing hybrid C-sections from waste and recycled composite materials

This paper investigates the performance of hybrid composites made from mixed waste plastics (wMP), recycled carbon fibre (rCF), and waste glass fibre (wGF). Two lay-up configurations with varying wGF and rCF contents were considered: one with approximately 7 vol% rCF (25 vol% wGF) and another with approximately 15 vol% rCF (9.4 vol% wGF). The tensile, compressive, and flexural performance of standard coupon specimens for both configurations were assessed, revealing that specimens with increased rCF content exhibited superior performance. Additionally, three hybrid C-sections, containing 15 vol% rCF, were thermoformed and subjected to axial compression. All three C-sections failed due to bearing failure, accompanied by some interlaminar delamination and material crushing at the loading ends. Their weight-specific load capacity surpassed that of similar sections published in the literature, such as ultra-thin-walled steel C-sections, by almost 95 %. A finite element model (FEM) of the C-section was developed and was able to predict reasonably well the stress versus strain response. These findings demonstrate that waste and recycled composite materials could serve as sustainable alternatives to ultra-thin-walled steel C-sections and other conventional materials commonly used in construction.

Production of cycloalkane-rich fuel by vacuum pyrolysis of mixed waste plastics using combined titanium and aluminum oxide: a preliminary investigation

The mitigation of plastic pollution constitutes one of the major challenges worldwide. Innovative research approaches have been solicited to improve the properties of fuel derived from plastic pyrolysis. The present study looks at the effect on the chemical composition of pyrolysis oil of the application in situ of a mixed metal oxide of titanium and aluminum in vacuum pyrolysis of mixed waste polyethylene, polypropylene, and polyethylene terephthalate. The experiment was performed at process parameters of 250 °C temperature, 79.9 Kpa vacuum pressure, and 1:10 catalyst-to-feedstock ratio, first without the mixed metal oxide (parent reaction) and then with the mixed metal oxide (modified reaction). The results showed that the presence of combined titanium and aluminum oxides in the reaction medium accounted for the presence of alkyl-substituted cycloalkanes at an area% of 33.97% in the liquid product, and a calorific value of 11,950 cal/gm was reported for the modified reaction. The parent reaction produced higher liquid and gaseous yields of 28.3% and 43.1% respectively while the modified reaction produced a greater percentage of char (23.8%) and residual wax(36.0%). The fuel properties of the liquid products obtained were equally determined.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review.

Plastics are widely used materials in our daily lives and various industries due to their affordability and versatility. The massive production of plastic waste, however, has recently emerged as a pressing environmental concern across all media. To address this, emerging technologies are being explored for the sustainable valorization of postconsumer plastic wastes including thermochemical, physical, and catalytic processes aimed at transforming them into higher value-added products. However, the chemical recycling of mixed plastic wastes poses a formidable challenge due to the diverse array of monomers and catalyst systems involved, each employing distinct mechanisms. Complicating matters further is that contaminants reduce catalytic efficacy, requiring rigorous and labor-intensive separation and purification processes to extract individual plastic streams from practical plastic waste mixtures. Consequently, the majority of such mixtures often end up in incineration and landfills, perpetuating environmental and societal challenges, such as leachate, carbon dioxide emissions, and other air pollutants. This review will introduce current technical developments available for recycling practical plastic waste mixtures through catalytic processes. The current challenges in process performance, low selectivity of the desired products, and catalyst deactivation from the catalysis of plastic waste mixtures are also discussed. Promising approaches to overcome the problems are suggested in future research directions.

Revolutionizing waste from household plastics to eco-friendly diesel alternatives through catalytic degradation with biogas utilization

The study tackled the pressing environmental issue of managing both biodegradable and non-biodegradable household plastic waste, aiming to convert this waste into valuable hydrocarbons, thus addressing critical concerns over plastic pollution and the quest for renewable energy sources. In the context of escalating environmental degradation and the urgent need for sustainable alternatives to fossil fuels, the ability to transform various forms of waste into energy presents a significant stride towards ecological and energy sustainability. Utilizing an innovative methodology, the research employed catalytic degradation of mixed plastic waste, leveraging fly ash as a catalyst and biogas produced from a combination of cow dung and kitchen waste as a renewable and sustainable heat source. This process was fine-tuned across several catalyst-to-polymer (cat/pol) ratios, specifically 0.10, 0.15, and 0.20, with detailed documentation of the degradation temperatures and yields of liquid and gaseous hydrocarbons for each 1 kg batch of plastic waste. Notably, at a cat/pol ratio of 0.20, a remarkable 100% conversion rate was achieved, highlighting the efficiency of this method. Following this, the resultant oil was segmented based on boiling points for further analysis and evaluation of its utility as a diesel fuel substitute. Significant findings include the highest liquid hydrocarbon yield of 65.1% at 378 °C, achieved with the 0.20 cat/pol ratio. Moreover, fractions boiling above 100 °C were identified to possess superior heating values and cetane numbers compared to conventional diesel, particularly the fraction boiling at 100 °C–150 °C (C2), which demonstrated optimal performance and combustion qualities. This fraction achieved a maximum brake thermal efficiency of 32.92%, exhibited low smoke density and hydrocarbon emissions of 48 HSU and 32ppm, but it also resulted in a significant increase in NOx emission. Among all the fractions, diesel C2 was observed to be the best in terms of performance & combustion and was lower in emission. The conclusions drawn underscore the method’s potential to mitigate plastic pollution and reduce fossil fuel reliance by converting both biodegradable and non-biodegradable waste into useful energy. This study’s novelty lies in its comprehensive approach to waste management and energy recovery, significantly advancing over previous literature by achieving a 100% conversion rate at a specific cat/pol ratio and optimizing the output for use as a diesel alternative. It stands out by producing a fraction with both high efficiency and lower emissions, offering a scalable, sustainable solution to waste management challenges and paving the way for future innovations in sustainable energy production.

Material Recycling of Plastics—A Challenge for Sustainability

The complexity of plastic polymers and even more so of additives has increased enormously in recent years. This makes the material recycling of plastic waste considerably more difficult, especially in the case of mixed plastic waste. Some additives have now been strictly regulated or even completely banned for good reasons (‘legacy additives’). Material or mechanical recycling generally uses old plastics that still contain these substances. Consequently, products that are manufactured using such recyclates are contaminated with these harmful substances. This poses a major challenge for sustainability, as there is a conflict of objectives between protecting the health of consumers, especially vulnerable groups, conserving resources and recycling, keeping material cycles ‘clean’ and destroying pollutants, and transporting them to a safe final sink. With regard to the first objective, we recommend avoiding the use of contaminated recyclates for products with intensive contact with consumers (‘contact-sensitive products’) until further notice. We also show that the climate policy challenges for the plastics (and chemical) industry necessitate defossilization (‘feedstock change’). This turnaround can only succeed if solely closed-loop recycling takes place in the future; recyclates should primarily replace virgin plastics. For material or mechanical recycling, this means that this can only work if used plastics with a high degree of homogeneity and known formulation are collected separately, as is already the case today with PET bottles. The objective of this article is to illustrate the increasing complexity of plastic polymers and additives, especially legacy additives, which will force a legislative readjustment of todays’ material recycling.

Closed-Loop Recycling of Mixed Plastics of Polyester and CO2-Based Polycarbonate to a Single Monomer.

Physical blending is an effective strategy for tailoring polymeric materials to specific application requirements. However, physically blended mixed plastics waste adds additional barriers in mechanical or chemical recycling. This difficulty arises from the intricate requirement for meticulous sorting and separation of the various polymers in the inherent incompatibility of mixed polymers during recycling. To overcome this impediment, this work furthers the emerging single-monomer - multiple-materials approach through the design of a bifunctional monomer that can not only orthogonally polymerize into two different types of polymers - specifically lactone-based polyester and CO2-based polycarbonate - but the resultant polymers and their mixture can also be depolymerized back to the single, original monomer when facilitated by catalysis. Specifically, the lactone/epoxide hybrid bifunctional monomer (BiLO) undergoes ring-opening polymerization through the lactone manifold to produce polyester, PE(BiLO), and is also applied to ring-opening copolymerization with CO2, via the epoxide manifold, to yield polycarbonate, PC(BiLO). Remarkably, a one-pot recycling process of a BiLO-derived PE/PC blend back to the constituent monomer BiLO in >99 % selectivity was achieved with a superbase catalyst at 150 °C, thereby effectively obviating the requirement for sorting and separation typically required for recycling of mixed polymers.