Special Issue "Polymer Recycling"

A special issue of Recycling (ISSN 2313-4321).

Deadline for manuscript submissions: closed (30 March 2021).

Special Issue Editor

Dr. Martin Schlummer
E-Mail Website
Guest Editor
Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Strasse 35, 85354 Freising, Germany
Interests: polymer recycling; recyclability; plastics in packaging; WEEE, ELV; plastic composite; fiber-reinforced plastics; recycling technologies; circular economy of plastics; hazardous compounds, POPs, SVHCs

Special Issue Information

Dear Colleagues,

As outlined in the EU Strategy for Plastics in a Circular Economy, recycling of polymers is an important but highly challenging issue, especially when it comes to post-consumer waste. In consequence, polymer recycling is a growing field of research and development covering concepts, technologies, and case studies in a wide field of branches.

Amongst others, Polymer Recycling addresses issues including:

  • Recovery of polymers from waste packaging, WEEE, ELV, building and construction, and post-industrial plastics and plastic composites;
  • Collection concepts and sorting technologies;
  • New pre-treatment and recycling technologies;
  • Recycling of mixed and multilayered plastics, e.g., from EoL packaging
  • Recycling of plastic composites including fiber-reinforced polymers, e.g., from automotive and building and construction sectors;
  • Dilemma of circular economy and safe disposal of legacy additives;
  • Odors and contaminants in recycled polymers;
  • Re-compounding and upgrading of recycled polymers;
  • Evaluation of environmental and economic performance of polymer recycling;
  • Process and equipment design for polymer recycling processes and its scale-up;
  • Design for and from recycling;
  • Application of recycled polymers in high-level products.

This Special Issue aims to highlight, through original research, review articles and case studies, an updated state-of-the-art of polymer recycling in a series of branches. This issue will report on innovative and disruptive recycling approaches that contribute a) to the general idea of plastics’ circularity and b) to a more sustainable plastic production that implements recycled polymers and reduces the CO2 footprint.

Dr. Martin Schlummer
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Recycling is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Polymers, commodities, and engineering polymers
  • Recycling technologies
  • Sorting technologies
  • Design
  • LCA
  • Case studies

Published Papers (6 papers)

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Research

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Article
Production of a PET//LDPE Laminate Using a Reversibly Crosslinking Packaging Adhesive and Recycling in a Small-Scale Technical Plant
Recycling 2021, 6(3), 47; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6030047 - 13 Jul 2021
Viewed by 669
Abstract
Multilayer packaging is an important part of the packaging market, but it is not recyclable with conventional methods since it is made of different thermodynamically immiscible materials. In this work, it was shown that it is possible to produce a PET//LDPE laminate in [...] Read more.
Multilayer packaging is an important part of the packaging market, but it is not recyclable with conventional methods since it is made of different thermodynamically immiscible materials. In this work, it was shown that it is possible to produce a PET//LDPE laminate in a pilot plant for lamination by using an adhesive consisting of maleimide- and furan-functionalized polyurethane prepolymers that cure through the Diels–Alder reaction. The material could then be delaminated in a small-scale recycling plant using a solvent-based recycling process by partially opening the Diels–Alder adducts through the influence of temperature. The PET and LDPE could be recovered without any adhesive residues before each material was regranulated, and in the case of the PE, a film was produced via cast film extrusion. The obtained PET granulate exhibited a slight, approximately 10%, decrease in molecular weight. However, since small amounts of LDPE could not be separated, compatibilization would still be required here for further use of the material. The obtained LDPE film was characterized by means of infrared spectrometry, differential scanning calorimetry, tensile testing, determination of the melt index, and molecular weight. The film showed lower crosslinking than usual for LDPE recycling and exhibited good mechanical properties. In this work, it was thus shown that upscaling of the laminate production with the modified adhesive and also its recycling at the pilot plant scale is possible and thus could be an actual option for recycling multilayer packaging. Full article
(This article belongs to the Special Issue Polymer Recycling)
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Article
Recycling Potential for Non-Valorized Plastic Fractions from Electrical and Electronic Waste
Recycling 2021, 6(2), 33; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6020033 - 19 May 2021
Cited by 2 | Viewed by 1055
Abstract
This paper describes a study for waste of electrical and electronic equipment (WEEE) to characterise the plastic composition of different mixed plastic fractions. Most of the samples studied are currently excluded from material recycling and arise as side streams in state-of-the-art plastics recycling [...] Read more.
This paper describes a study for waste of electrical and electronic equipment (WEEE) to characterise the plastic composition of different mixed plastic fractions. Most of the samples studied are currently excluded from material recycling and arise as side streams in state-of-the-art plastics recycling plants. These samples contain brominated flame retardants (BFR) or other substances of concern listed as persistent organic pollutants or in the RoHS directive. Seventeen samples, including cathode ray tube (CRT) monitors, CRT televisions, flat screens such as liquid crystal displays, small domestic appliances, and information and communication technology, were investigated using density- and dissolution-based separation processes. The total bromine and chlorine contents of the samples were determined by X-ray fluorescence spectroscopy, indicating a substantial concentration of both elements in density fractions above 1.1 g/cm3, most significantly in specific solubility classes referring to ABS and PS. This was further supported by specific flame retardant analysis. It was shown that BFR levels of both polymers can be reduced to levels below 1000 ppm by dissolution and precipitation processes enabling material recycling in compliance with current legislation. As additional target polymers PC and PC-ABS were also recycled by dissolution but did not require an elimination of BFR. Finally, physicochemical investigations of recycled materials as gel permeation chromatography, melt flow rate, and differential scanning calorimetry suggest a high purity and indicate no degradation of the technical properties of the recycled polymers. Full article
(This article belongs to the Special Issue Polymer Recycling)
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Article
Textile Recognition and Sorting for Recycling at an Automated Line Using Near Infrared Spectroscopy
Recycling 2021, 6(1), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6010011 - 08 Feb 2021
Cited by 2 | Viewed by 1470
Abstract
In order to add value to recycled textile material and to guarantee that the input material for recycling processes is of adequate quality, it is essential to be able to accurately recognise and sort items according to their material content. Therefore, there is [...] Read more.
In order to add value to recycled textile material and to guarantee that the input material for recycling processes is of adequate quality, it is essential to be able to accurately recognise and sort items according to their material content. Therefore, there is a need for an economically viable and effective way to recognise and sort textile materials. Automated recognition and sorting lines provide a method for ensuring better quality of the fractions being recycled and thus enhance the availability of such fractions for recycling. The aim of this study was to deepen the understanding of NIR spectroscopy technology in the recognition of textile materials by studying the effects of structural fabric properties on the recognition. The identified properties of fabrics that led non-matching recognition were coating and finishing that lead different recognition of the material depending on the side facing the NIR analyser. In addition, very thin fabrics allowed NIRS to penetrate through the fabric and resulted in the non-matching recognition. Additionally, ageing was found to cause such chemical changes, especially in the spectra of cotton, that hampered the recognition. Full article
(This article belongs to the Special Issue Polymer Recycling)
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Article
Sustainable Additive Manufacturing: Mechanical Response of High-Density Polyethylene over Multiple Recycling Processes
Recycling 2021, 6(1), 4; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6010004 - 04 Jan 2021
Cited by 2 | Viewed by 1361
Abstract
Polymer recycling is nowadays in high-demand due to an increase in polymers demand and production. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the recyclability of high-density polyethylene (HDPE), one [...] Read more.
Polymer recycling is nowadays in high-demand due to an increase in polymers demand and production. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the recyclability of high-density polyethylene (HDPE), one of the most recycled materials globally, for use in additive manufacturing (AM). A thorough investigation was carried out to determine the effect of the continuous recycling on mechanical, structural, and thermal responses of HDPE polymer via a process that isolates the thermomechanical treatment from other parameters such as aging, contamination, etc. Fused filament fabrication (FFF) specimens were produced from virgin and recycled materials and were experimentally tested and evaluated in tension, flexion, impact, and micro-hardness. A thorough thermal and morphological analysis was also performed. The overall results of this study show that the mechanical properties of the recycled HDPE polymer were generally improved over the recycling repetitions for a certain number of recycling steps, making the HDPE recycling a viable option for circular use. Repetitions two to five had the optimum overall mechanical behavior, indicating a significant positive impact of the HDPE polymer recycling aside from the environmental one. Full article
(This article belongs to the Special Issue Polymer Recycling)
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Article
An Additive Model to Predict the Rheological and Mechanical Properties of Polypropylene Blends Made by Virgin and Reprocessed Components
Recycling 2021, 6(1), 2; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6010002 - 02 Jan 2021
Cited by 4 | Viewed by 1186
Abstract
In this work, an additive model for the prediction of the rheological and mechanical properties of monopolymer blends made by virgin and reprocessed components is proposed. A polypropylene sample has been reprocessed more times in an extruder and monopolymer blends have been prepared [...] Read more.
In this work, an additive model for the prediction of the rheological and mechanical properties of monopolymer blends made by virgin and reprocessed components is proposed. A polypropylene sample has been reprocessed more times in an extruder and monopolymer blends have been prepared by simulating an industrial process. The scraps are exposed to regrinding and are melt reprocessed before mixing with the virgin polymer. The reprocessed polymer is, then, subjected to some thermomechanical degradation. Rheological and mechanical experimental data have been compared with the theoretical predictions. The results obtained showed that the values of this simple additive model are a very good fit for the experimental values of both rheological and mechanical properties. Full article
(This article belongs to the Special Issue Polymer Recycling)
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Review

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Review
An Overview of Plastic Waste Generation and Management in Food Packaging Industries
Recycling 2021, 6(1), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/recycling6010012 - 12 Feb 2021
Cited by 10 | Viewed by 3189
Abstract
Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. This has led to unprecedented amounts of mixed types of plastic waste entering the environment unmanaged. Packaging plastics account for half of the global [...] Read more.
Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. This has led to unprecedented amounts of mixed types of plastic waste entering the environment unmanaged. Packaging plastics account for half of the global total plastic waste. This paper seeks to give an overview of the use, disposal, and regulation of food packaging plastics. Demand for food packaging is on the rise as a result of increasing global demand for food due to population growth. Most of the food packaging are used on-the-go and are single use plastics that are disposed of within a short space of time. The bulk of this plastic waste has found its way into the environment contaminating land, water and the food chain. The food industry is encouraged to reduce, reuse and recycle packaging materials. A wholistic approach to waste management will need to involve all stakeholders working to achieve a circular economy. A robust approach to prevent pollution today rather than handling the waste in the future should be adopted especially in Africa where there is high population growth. Full article
(This article belongs to the Special Issue Polymer Recycling)
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