Recycled Plastic Research Articles

Circular Economy and Chemical Conversion for Polyester Wastes.

Polyester waste in the environment threatens public health and environmental ecosystems. Chemical recycling of polyester waste offers a dual solution to ensure resource sustainability and ecological restoration. This minireview highlights the traditional recycling methods and novel recycling strategies of polyester plastics. The conventional strategy includes pyrolysis, carbonation, and solvolysis of polyesters for degradation and recycling. Furthermore, the review delves into exploring emerging technologies including hydrogenolysis, electrocatalysis, photothermal, photoreforming, and enzymatic for upcycling polyesters. It emphasizes the selectivity of products during the polyester conversion process and elucidates conversion pathways. More importantly, the separation and purification of the products, the life cycle assessment, and the economic analysis of the overall recycling process are essential for evaluating the environmental and economic viability of chemical recycling of waste polyester plastics. Finally, the review offers perspective into the future challenges and developments of chemical recycling in the polyester economy.

Selective Degradation of Polyethylene Terephthalate Plastic Waste Using Iron Salt Photocatalysts.

Plastic pollution poses a significant challenge to environmental conservation. Efficient recycling of plastic is a key strategy to address this issue. Polyethylene terephthalate (PET), commonly found in plastic bottles, represents a substantial portion of plastic waste. Consequently, the efficient degradation and recycling of PET is crucial for the sustainable development of society. However, the implementation of methods for PET depolymerization and recycling typically necessitates alkaline/acidic pre-treatment and significant energy input for heating. Here, we propose a gentle, and highly efficient photocatalysis approach for selectively degrading PET plastic waste into terephthalic acid (TPA) in high yield (up to 99%) using cost-effective iron salts. Notably, this method achieved excellent selectivity with high TON and TOF values, applying oxygen or air as environmentally friendly oxidants. In addition, the solvent can be recycled without compromising the TPA yield, and large-scale reactions can be performed smoothly.

Fire parameters of recycled plastic pellets

AbstractDuring the recycling process, waste plastic undergoes various processes that change its geometry. The thermal properties and fire behaviour of plastic in different geometries has not been widely studied. This paper aims to determine critical thermal properties of plastic pellets made of recycled plastic. For this paper, cone calorimeter tests of various volumes of recycled plastic pellets of low‐ and high‐density polyethylene and polypropylene were conducted. During these tests, the heat release rate (HRR), mass loss rate and time‐to‐ignition were measured, thereafter the heat of combustion (HOC) was calculated. A calibration of suitable time‐to‐ignition equations is carried out. The average HRR is between 353 and 581 kW/m2 with an external heat flux of 50 kW/m2. The measured time‐to‐ignition values ranged between 27 s at 50 kW/m2 and just more than 90 s at 25 kW/m2. Values obtained analytically from the thermally thin time‐to‐ignition equations for these materials describe ignition well, which appears to be due to the particulate nature of the samples. The HOC (40–41 MJ/kg) shows good agreement with the HOC for virgin plastic found in literature. These properties can be used as a basis for material characterisation, and further testing will be done before using this as simulation inputs to determine how bulk stored plastic pellets will behave in the event of a fire.

The Properties of Bricks Made from Recycled HDPE

Plastic waste, particularly high-density polyethylene (HDPE), poses significant environmental challenges due to its non-biodegradable nature. Recycling HDPE into building materials, such as bricks, offers a sustainable solution to mitigate these impacts. This study investigates the properties of bricks made from recycled HDPE, focusing on their compressive strength, water absorption, and durability. The results indicate that HDPE bricks exhibit superior mechanical properties, including higher compressive strength and lower water absorption compared to traditional clay bricks. These bricks are lightweight, cost-effective, and demonstrate excellent durability, making them a viable alternative for sustainable construction. The research highlights the potential of recycled HDPE bricks in reducing plastic waste and promoting environmental sustainability. The intensifying generation of plastic waste presents a significant environmental challenge worldwide. Plastic waste, due to its non-biodegradable nature, contributes to land and water pollution, requiring the exploration of sustainable waste management solutions. Recycling plastic waste into building materials, such as bricks, offers a potential solution to mitigate environmental impacts. This research aimed to investigate the integration of plastic waste into building materials through a comprehensive study using experimental testing, software analysis, and structural design. The ETAB analysis demonstrated that the HDPE model exhibited lower bending moments and axial loads compared to the concrete model, suggesting superior mechanical properties and load-carrying capacity. This research contributes to the understanding of the behaviour and performance of plastic bricks in structural applications, enabling the development of sustainable and efficient building designs that incorporate plastic waste materials. Key Words: Plastic Waste, Environmental Challenge, Non-Biodegradable, Sustainable Solutions, Experimental Study, Plastic Bricks, Alternative Building Materials, Methodology, Comparable Strength, Plastic Waste Crisis.

Photooxidation of Polystyrene into High‐Value Chemicals

Plastics play a crucial role in the survival and advancement of human civilization. However, the increasing challenge of plastic pollution presents significant obstacles. Disposal methods such as incineration and landfilling result in substantial resource wastage and pose potential environmental hazards. The slow progress in recycling and reusing waste plastics hinders their industrial application and effective response to environmental crises. Photocatalysis offers promising solutions for the future of plastic recycling, particularly with the recent increase in photocatalytic degradation methods for polystyrene (PS). This review provides a comprehensive overview of the latest advancements in the photooxidation of PS into high‐value chemicals.

Super Tough PA6/PP/ABS/SEBS Blends Compatibilized by a Combination of Multi-Phase Compatibilizers

Development of multi-component blends to prepare high-performance polymer materials is still challenging, and is a key technology for mechanical recycling of waste plastics. However, a multi-phase compatibilizer is prerequisite to create high-performance multi-component blends. In this study, POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) compatibilizers are prepared via melt-grafting of maleic anhydride (MAH) and styrene (St) dual monomers to polyolefin elastomer (POE) and poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), respectively. Subsequently, these compatibilizers are utilized to compatibilize the PA6/PP/ABS/SEBS quaternary blends through melt-blending. When POE-g-(MAH-co-St) and SEBS-g-(MAH-co-St) are added, respectively, both can promote the distribution of the dispersed phases, significantly reducing the dispersed phase size. When adding 10 wt% POE-g-(MAH-co-St) and 10 wt% SEBS-g-(MAH-co-St) together, compared to the non-compatibilized blend, the fracture strength, fracture elongation, and impact strength surprisingly increased by 106%, 593%, and 823%, respectively. It can be attributed to the hierarchical interfacial interactions which facilitate gradual energy dissipation from weak to strong interfaces, resulting in the improvement of mechanical properties. The synergistic effect of the enhanced phase interfacial interactions and toughening effect of elastomer compatibilizer achieved simultaneous growth in strength and toughness.

Plastic waste in dense asphalt mixes for road pavements

Recycling plastic waste in asphalt pavements records increasing statistic figures of application during the last decade worldwide. Due to environmental constraints, but also, to some beneficial properties of plastic waste, recycling in asphalt tends to become current practice, in several countries. In the Aristotle University of Thessaloniki (AUTH), the first attempt to produce asphalt mix using plastic waste consisted of mixing recycled plastic flakes with non-modified binder. Following an asphalt mix design in the laboratory, the whole mass of conventional aggregates was replaced by PET flakes. Recycled PET flakes were chosen to be introduced in the asphalt mix since they are hard, resilient and water repellent. Bitumen emulsion was first preferred as a binder to produce a cold asphalt mix. At a second stage of experimental research, plastic flakes replaced a part of the limestone sand while conventional asphalt 50/70 was used as a binder. At this stage, the experimental research provided more encouraging outcomes. Stability of asphalt mixes decreases as the plastics content in the mix increases, but all recorded values were still within limits of acceptance. At a third stage of research, LDPE recycled material of fine gradation was used to replace a part of the asphalt binder in dense mixes. The objective was to produce a modified binder and a more durable asphalt structure. Test results showed a significant improvement of the performance of asphalt mixes, in terms of strength and deformability of the asphalt mix structure. The research is completed by comparing the conventional techniques with the outcomes of the recycling process and by delineating potential fields of application of the recycled plastics in asphalt pavements.

Providing a new route for chemical recycling of plastics by aspen plus simulation, energy, and its carbon dioxide emissions analysis

Providing a new route for chemical recycling of plastics by aspen plus simulation, energy, and its carbon dioxide emissions analysis

Effects of acid and sulphate attack on concrete containing recycled plastic waste fine aggregate

Effects of acid and sulphate attack on concrete containing recycled plastic waste fine aggregate

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

Exploratory analysis of influential factors in the choices of using single-use or reusable cups in vending

PurposeThis study investigates the variables that play a role in the purchase intention of a hot beverage at a vending machine (1) served in a 100% recyclable plastic single-use cup, (2) served in a biodegradable paper single-use cup and (3) served in personal, reusable cups brought by customers. The variables considered are perceived environmental benefits (PEBs), perceived contamination risk (PCR), social norms (SNs), value for money (VM), gender and age. The secondary objective is to investigate respondents’ perceptions of these cups using the first four variables and to assess the existence of significant differences among them.Design/methodology/approachFor the first purpose, three separate logistic regression models on purchase intention were created, considering PEBs, PCR, SNs, VM, gender and age as independent variables. For the second purpose, the analysis relied on Friedman’s nonparametric test. The entire survey was conducted in Italy on a sample of 1,006 consumers.FindingsSNs and VM are the variables with the greatest influence on final purchase intention. PEBs seem to have an effect only in the case of the plastic and paper single-use cups, while PCR only in the case of the reusable cup. Neither gender nor age seem to play a significant role in final purchase intention. Friedman’s test revealed significant differences among the three cup types in terms of perceptions, but not in the case of the PCR variable.Originality/valueThe study is the first to compare new single-use cups with reusable cups from vending machines in terms of consumers’ perceptions and preferences.

Dynamic covalent epoxy network of hyperbranched-synergistic-supramolecular: Catalyst-free reprocessing, and application in carbon fiber composites recycling

Plastic recycling, especially the recycling of thermosets, is a crucial step towards improving waste management and achieving economic recycling. Here, a method utilizing non-covalent supramolecular interactions and synergistic hyperbranched structures is reported to endow transesterification-based thermosetting materials with recyclability in the absence of a catalyst. A hyperbranched epoxy resin curing agent (HPCA) containing amide bonds, terminated by amine and ester, was designed and synthesized, and further cured with bisphenol A epoxy resin. The hyperbranched topological structure and its abundant amide bonds contribute to the formation of a dense hydrogen bonding network, enhancing the reprocessability, thermal, and mechanical properties of the material. As a result, the resin can be reprocessed by hot pressing at 190 °C and 10 MPa for 40 min without catalyst. Moreover, amide and ester bonds endow resin materials with excellent degradation performance in alkaline solutions, laying the foundation for the recycling and utilization of carbon fibers in composite materials.

Recycling of Plastics in the Automotive Sector and Methods of Removing Paint for Its Revalorization: A Critical Review

The presence of plastics in the automotive industry is increasingly significant due to their lightweight nature, which contributes to reducing fuel consumption and CO2 emissions while improving versatility and mechanical properties. Polypropylene (PP) and other polyolefins are among the most commonly used materials, especially for components such as bumpers. The use of composite materials, i.e., a combination of different polymers, improves the properties through synergistic effects, thereby also improving the performance of the final product. In the automotive industry, PP reinforced with 20% talc or CaCO3 is commonly used. The mechanical recycling of polypropylene bumpers is the most common type of recycling. However, challenges arise during this process, such as the presence of impurities like paint, chemical contaminants from previous use, and polymeric impurities from different polymers mixed into the polymer matrix, among others. Paint affects both the aesthetic quality and the mechanical and intrinsic properties of the recycled material. This review aims to analyze the main methods reported in the literature, focusing on those with low environmental impact. Furthermore, these methods are classified according to their capacity, effectiveness, substrate damage, environmental hazards, and economic feasibility. It also aims to offer a comprehensive overview of the mechanical recycling of plastic waste in the automotive industry.

Attitude of Romanian students and their families concerning waste management

Abstract Waste recovery, recycling included, is an important step in waste management, preceding final disposal. In 2018, according to Eurostat, the recycling rate of municipal waste was 47% in the European Union and only 11.1% in Romania. Thus governmental institutions have implemented new measures in order to reduce environmental pollution by ineffective waste management. In 2022, 535 students aged 22-24.5 years, males and females, studying in Craiova (one of the six largest academic cities of Romania), were asked to answer an 18-item questionnaire regarding their and their families’ attitude towards waste recycling. Most of the students (60.7%) were residents in the university city, while the others - in smaller cities or in villages of the region. Only 38.3% of the subjects (N = 205) declare their families recycle waste; the most common excuse for no-recycling (37.8%) is the lack of recycle bins in the house proximity. Only 20 families (3.7%), all of them living in Craiova, take the fried oil to collecting points in supermarkets; most of the others eliminate it in the sewerage system, especially those from outside the city (p < 0.01). Seventy-five students (14%) are not able to mention any recent measure taken by the government in order to reduce plastics environmental pollution; the others discuss about the increased number of recycle bins around the city (53.2%), recycling of single-use plastics (34.5%) or use of biodegradable bags (25.2%). No-recycling (42%), using daily his/her own car (18.7%, p < 0.01 males vs. females), using too much plastics (11.2%) are the most frequent self-reported students’ disregards for the environment. Most of the subjects consider environmental health of essential importance (88.7%) and would like to participate in environment protection actions (92.5%). Romanian students seem to have a positive attitude and like to be involved in the environment protection, without a significant influence regarding the gender and the residence place. Key messages • Education and information are essential tools to make people ecologically aware. • Recycling is one of the best ways to have a positive impact on both natural and community environment.

Look before you leap: Are increased recycling efforts accelerating microplastic pollution?

AbstractTo fight plastic pollution and reach net‐zero ambitions, policy and industry set goals to increase the recycling of plastics and the recycled content in products. While this ideally reduces demand for virgin material, it also increases pressure on recyclers to find suitable endmarkets for the recyclate. This may lead to two effects: a multiplication of recycled content in applications already made of plastic and a substitution of non‐plastic materials with cheap, low‐quality recyclate. Both areas of application may be sources of microplastic (MP) pollution. Combined with the inherent degradation of recyclate during its lifecycle, but also during recycling, we expect the increase in recycled content will subsequently lead to an increase in MP pollution. We propose a framework to investigate the risk of MP generation through plastic applications throughout their subsequent lifecycle of production, use phase, and end of life. We apply the framework to two prominent examples of recyclate endmarkets, that is, textiles and wood–plastic, and point out where the degradation effects can cause higher release. To conclude, we outline a research agenda to support policymakers in their decision making on specifying targets for recycling and recycled content.

Economic instruments for reducing the use of plastic bags in the state of Pará, Brazil

The state of Pará has prohibied the sale and distribution of conventional plastic bags to mitigate their socio-environmental impact. This article aims to suggest economic incentives to assist State Law 8902/2019 in diminishing plastic bag consumption. This study employed the SWOT Matrix analysis to develop two economic instruments based on the externality precepts defined by Arthur Pigou and Ronald Coase. The initial proposal, derived from Pigou, involved of a “tax exemption for plastic recycling enterprises”, whereas the subsequente proposal, based on Coase, stipulated “offering discounts to customers who refrain from utilising plastic bags”. Both instruments demonstrated potential for yielding favorable outcomes when integrated with Law 8902/2019; nevertheless, their efficacy relies on an effective selective collecting system and the advancement of environmental education.

A Business Management Model in the Circular Economy: Technological Solutions for Plastic Recycling

Objectives: this article develops a model for managing business processes in a circular economy using technologies for plastic recycling. Theoretical Framework: The theoretical idea and basis of the article consists in the development of project management methodology, process approach in the closed-loop economy, development of methods and economic tools aimed at effective resource management taking into account waste reduction and increased reuse of plastic fractions in Municipal Solid Waste (MSW). The application of digital technologies and solutions in the context of business process management in the field of plastics recycling will be substantiated, which will allow to identify new opportunities and reserves for optimising business processes in this field, increasing the efficiency of resource use, improving the environment and reducing costs. Method: the work uses a project approach, a process approach, digital modeling methods, and the “polluter pays” method. To implement the process approach, it is proposed to use the concept of Business Process Management (BPM). Competent business process management allows the company to react quickly to changing market conditions and customer orientation. Digital modelling in this paper means the representation of actions in the form of business processes in the organisation of solid waste management, the 'polluter pays' method means the economic assessment and accounting of environmental damage in waste management in the costs of business processes. Results and Discussion: The results of the study can be used to introduce the process approach to plastics recycling in individual regions and countries for the development of a green economy. According to the estimates of the authors, the optimisation and cost reduction of business processes, taking into account the environmental factor and the increase of the revenue part of the project from the reuse and inclusion in the economic turnover of plastic waste recycling products on the scale of the considered city (population of 1800 thousand people, area of 2856 ha, 18.14 tonnes of plastic waste accumulated per day) will reduce the costs of business process management by more than 200 thousand euros. Research Implications: the results of the study can be used to justify projects for the processing and recycling of solid municipal waste, including plastic waste, to introduce environmentally friendly production, to reduce the negative impact on the environment, to develop a process approach to the organisation of all activities for the collection of plastic waste in the city, district. In addition, the application of the proposed approach allows to obtain economic benefits for companies through the sale of secondary resources for the processing of plastic waste, as well as to reduce the negative impact on the environment. Originality/ Value: The originality of the research and its value lies in a new scientific formulation of the problem of reducing environmental pollution from plastic waste through the use of business processes in the field of plastic recycling and digital solutions, as well as the possibility of practical application of the results obtained in the field of green economy.

An appropriate artificial intelligence technique for plastic materials recycling using bipolar dual hesitant fuzzy set

Plastic recycling has become more important than ever as the globe struggles with growing environmental issues. This research explores the significant environmental impact of recycling plastic and its growing relevance. The pervasive material known as plastic presents a complex risk to both human health and ecosystems in contemporary life. It exacerbates problems including marine pollution, habitat damage, and wildlife entanglement because of its persistence in landfills and seas, which leads to serious ecological deterioration. In addition, producing plastic uses a lot of energy and produces a lot of greenhouse gas emissions, which exacerbate climate change. Through the use of multi-criteria decision making (MCDM), this study emphasizes how vital it is to support recycling activities in order to protect the environment and promote a sustainable future. The elimination and choice ex-pressing reality (ELECTRE) approach is used to rank the alternatives in this proposed research study that employs bipolar dual hesitant fuzzy sets (BDHFs). The most efficient and versatile outranking method for making decisions is the BDHF-ELECTRE approach. The weights of environment, economic, social, technical, and finally safety is computed using the entropy distance metric. The economic factor received the highest score of 0.2945 among the other factors since economic considerations are crucial in choosing the most efficient plastic recycling method, as they ensure sustainability, cost-effectiveness, resource allocation, and overall feasibility in managing plastic waste. The decision-makers determined that the mechanical recycling approach ought to be prioritized over all others for the efficient recycling of plastic waste. The robustness of the system is examined in the sensitive and comparative analyses. The proposed MCDM technique thus presents a viable solution, mitigating the adverse effects of plastic waste by conserving resources, reducing energy consumption, and curbing pollution.

The emission and physicochemical properties of airborne microplastics and nanoplastics generated during the mechanical recycling of plastic via shredding

This study examined the emission and physicochemical properties of microplastics and nanoplastics (MPs/NPs) generated during shredding, which is regularly used in mechanical recycling. Waste and new polyethylene terephthalate, polypropylene, and high-density polyethylene were investigated herein for a total of six categories. The concentration and size distribution of particles were measured using two spectrometer instruments, and morphology and elemental composition of emitted particles were analyzed with microscopy and spectroscopy. This study found that number concentrations in both submicron and micron sizes of respirable particles were 3–2910× higher during periods of shredding than pre-shredding background concentrations. Maximum concentrations of particles within 10–420 nm, across all six categories, ranged from 22,000- to 1,300,000-particles/cm3 during shredding, compared to average background levels of 700 particles/cm3. Maximum concentrations of particles within 0.3 to 10 μm, across all six categories, ranged from 24- to 2000-particles/cm3 during shredding, compared to average background levels of 2 particles/cm3. Waste plastics consistently generated higher emissions than their new counterparts, which is attributed to the labels, adhesives, and increased additives incorporated into the waste plastic. Morphology varied drastically between particles and an elemental composition analysis found that the samples consisted primarily of C and O, representing the polymer material, as well as Na, Mg, Al, Si, Cu, Cl, K, Ca, Ti, Fe, Rb, and Br representing additives, label, and other contaminates. The shredding of plastic has the potential to expose workers to elevated concentrations of airborne MPs/NPs, especially those between 10 and 100 nm.

Overcoming barriers to proactive plastic recycling toward a sustainable future

The plastics sector, accounting for a significant portion of global emissions, presents a challenge and an opportunity in achieving carbon neutrality. Despite Japan's commendable polyethylene terephthalate (PET) bottle recycling rates, most plastics are thermally recycled, creating environmental issues. This study proposes an evaluation framework to enhance recycling, aligned with end-user preferences and fostering a circular plastics economy. Employing a mixed-methods approach, this study conducts fieldwork including interviews with plastic recyclers and analysis of industry data. A weighted sum multicriteria analysis integrating end-user preferences, recycling effectiveness, and market dynamics is utilized. Systemic, process, and policy challenges were shown to hinder sustainable recycling practices, while varying willingness to pay, emission and cost reduction potentials, among acceptability and sectoral diversity informed priority plastic types for recycling. Multicriteria analysis showed that although PET is favored by end users, Polyoxymethylene (POM) emerges as a potential priority target for manufacturers and recyclers. Sensitivity analysis underscores the potential impact of establishing or enhancing willingness to pay (WTP) toward certain plastic types. Moreover, manufacturer and recycler evaluations suggest a broader willingness to recycle plastics than previously assumed. The proposed evaluation framework offers insights toward plastic recycling strategies. Policy interventions such as sustained subsidies for recyclers, market incentives leveraging WTP preferences, and technological advances, including chemical recycling and the broadening of plastic type recycling in line with user and manufacturer preferences, could all contribute to promoting sustainable plastic recycling practices.