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Polymers
Special Issues
Recycling Polymers: The Path to a Sustainable Future
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Recycling Polymers: The Path to a Sustainable Future

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (20 December 2022) | Viewed by 7380

Special Issue Editors

Dr. Emilia Garofalo

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Salerno, Fisciano (SA), Italy
Interests: flexible packaging recycling; upgrading strategies for recycled mixed polymers; processing–structure–property relationship of polymer nanocomposites; biodegradable and active technologies
Prof. Dr. Loredana Incarnato

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Salerno, Fisciano, Italy
Interests: innovative and sustainable packaging solutions based on biopolymers; recycled polymers; active polymeric systems for food-packaging applications and nanotechnologies
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Currently, the growing consumption of polymer products creates large quantities of waste materials resulting in public concern in the environment and people’s life. The recycling process represents the best way to manage plastic waste in a circular economy approach and for a more sustainable future. At present, mechanical recycling is the technique most commonly used for the recovery of polymer waste, but one main critical issue consists in the progressive thermomechanical degradation of recycled material. In this regard, chemical recycling might be a complementary solution to sit alongside traditional mechanical recycling. Its main advantage lays in the possibility of giving outputs comparable to those of virgin materials. However, most chemical recycling technologies are still in the development phase—they are often cost-intensive, the input waste flows must be cleaner than previously thought, and moreover, their environmental viability has not been proven.

The aim of this Special Issue is to highlight the current research strategies and future perspectives in polymer waste recycling as a key factor to turn plastics into sustainable materials.

In this Special Issue, original research articles and reviews are welcome. Research areas may include (but not be limited to) the following:

  • Novel and innovative techniques in sorting plastic waste to obtain more homogeneous streams for recycling;
  • Recycling of the most challenging plastic waste streams, such as flexible packaging, mixed plastics and so on;
  • Quality assessment of recycled plastics;
  • Efficient and effective strategies (compatibilization, nanotechnology, etc.) For upgrading the performances (processability, mechanical and functional properties, food-contact suitability, etc.) of recycled plastics;
  • Strategies to tackle the hygroscopicity and odor issues of recycled polymers;
  • Progress in chemical recycling techniques.

Dr. Emilia Garofalo
Prof. Dr. Loredana Incarnato
Guest Editors

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 submissions that pass pre-check are 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. Polymers is an international peer-reviewed open access semimonthly 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 2700 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

  • polymer recycling
  • mechanical recycling
  • chemical recycling
  • compatibilization strategies
  • mixed plastics waste
  • flexible packaging recycling
  • food-contact suitability of recycled plastics

Published Papers (3 papers)

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Research

18 pages, 6961 KiB  
Article
Assessment of Melt Compounding with Zeolites as an Effective Deodorization Strategy for Mixed Plastic Wastes and Comparison with Degassing
by Emilia Garofalo, Leonardo Taurino, Luciano Di Maio, Heinz C. Neitzert and Loredana Incarnato
Polymers 2023, 15(8), 1858; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15081858 - 13 Apr 2023
Viewed by 2214
Abstract
The emission of off-odors from mechanically recycled plastics severely limits their re-introduction into the market for the production of new objects, for the same use or even for less demanding applications, thus hindering the implementation of an effective circular economy for plastics. The [...] Read more.
The emission of off-odors from mechanically recycled plastics severely limits their re-introduction into the market for the production of new objects, for the same use or even for less demanding applications, thus hindering the implementation of an effective circular economy for plastics. The addition of adsorbing agents during the extrusion of polymers represents one of the most promising strategy to reduce the odorous emissions of plastics, due to its characteristics of cost-effectiveness, flexibility and low energy consumption. The novelty of this work lies in the assessment of zeolites as VOC adsorbents during the extrusion of recycled plastics. They appear more suitable than other types of adsorbents, due to their ability to capture and “hold” the adsorbed substances at the high temperatures of the extrusion process. Moreover, the effectiveness of this deodorization strategy was compared with the traditional degassing technique. Two types of mixed polyolefin wastes, coming from completely different collection and recycling processes, were tested: Fil-S (Film-Small), deriving from post-consumer flexible films of small size, and PW (pulper waste), which is the residual plastic waste obtained from the paper recycling process. The melt compounding of the recycled materials with two micrometric zeolites (zeolite 13X and Z310) resulted as more effective in the off-odors removal with respect to degassing. In particular, the highest reduction (−45%) of the Average Odor Intensity (AOI) was measured for both PW/Z310 and Fil-S/13X systems at 4 wt% of the zeolites’ amount, compared with the corresponding untreated recyclates. Finally, by combining degassing and melt compounding with zeolites, the best result was obtained for the composite Fil-S/13X, whose Average Odor Intensity resulted as quite close (+22%) to the one of the virgin LDPE. Full article
(This article belongs to the Special Issue Recycling Polymers: The Path to a Sustainable Future)
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17 pages, 6164 KiB  
Article
Effect of Gamma Radiation on the Processability of New and Recycled PA-6 Polymers
by Carlos González Niño, Julio Vidal, Martina Del Cerro, Lucía Royo-Pascual, Gonzalo Murillo-Ciordia and Pere Castell
Polymers 2023, 15(3), 613; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15030613 - 25 Jan 2023
Cited by 4 | Viewed by 2371
Abstract
The growing quantities of plastic waste have raised environmental concerns, with almost a quarter of disposed plastics being sent to landfill. This has motivated research efforts into various recycling technologies to ease dependence on fossil resources, increasing circularity. Irradiation of various kinds, such [...] Read more.
The growing quantities of plastic waste have raised environmental concerns, with almost a quarter of disposed plastics being sent to landfill. This has motivated research efforts into various recycling technologies to ease dependence on fossil resources, increasing circularity. Irradiation of various kinds, such as electron beam, beta and gamma rays, has been studied in the past as a way of revamping end-of-life polymer properties. The present work focuses on the effects of gamma radiation on the processability of new and recycled polymers, which is intimately linked with their rheological properties. In this study, both virgin and recycled polymers were irradiated under different radiation doses and the effects of the radiation on their viscosity assessed and compared. Results were analyzed making use of different theoretical relationships, and the causes of the changes in rheology were investigated by means of various characterization techniques, such as GPC, FTIR, EPR and DSC. Finally, the rheological curves of all samples were fitted to the Ostwald–de Waele relationship and the dependence of its parameters on the absorbed dose fitted to a function. Full article
(This article belongs to the Special Issue Recycling Polymers: The Path to a Sustainable Future)
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22 pages, 8206 KiB  
Article
Mechanical Recycling of Ethylene-Vinyl Acetate/Carbon Nanotube Nanocomposites: Processing, Thermal, Rheological, Mechanical and Electrical Behavior
by Ionut-Laurentiu Sandu, Felicia Stan and Catalin Fetecau
Polymers 2023, 15(3), 583; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15030583 - 23 Jan 2023
Cited by 3 | Viewed by 1834
Abstract
Recycling polymer/carbon nanotube (CNT) nanocomposites is not well common, despite a growing interest in using polymer/carbon nanotube (CNT) nanocomposites in industrial applications. In this study, the influence of mechanical recycling on the thermal, rheological, mechanical and electrical behavior of ethylene-vinyl acetate (EVA)/CNT nanocomposites [...] Read more.
Recycling polymer/carbon nanotube (CNT) nanocomposites is not well common, despite a growing interest in using polymer/carbon nanotube (CNT) nanocomposites in industrial applications. In this study, the influence of mechanical recycling on the thermal, rheological, mechanical and electrical behavior of ethylene-vinyl acetate (EVA)/CNT nanocomposites is investigated. EVA/CNT nanocomposite with different amounts of CNTs (1, 3 and 5 wt.%) was subjected to mechanical grinding and reprocessing by injection molding in a close-loop up to three cycles, and the changes induced by mechanical recycling were monitored by Differential Scanning Calorimetry (DSC), capillary rheology, scanning electron microscopy (SEM), electrical resistance and tensile tests. It was found that the EVA/CNT nanocomposites did not exhibit significant changes in thermal and flow behavior due to mechanical recycling and reprocessing. The recycled EVA/CNT nanocomposites retain close to 75% of the original elastic modulus after three recycling cycles and about 80–90% in the tensile strength, depending on the CNT loading. The electrical conductivity of the recycled nanocomposites was about one order of magnitude lower as compared with the virgin nanocomposites, spanning the insulating to semi-conducting range (10−9 S/m–10−2 S/m) depending on the CNT loading. With proper control of the injection molding temperature and CNT loading, a balance between the mechanical and electrical properties of the recycled EVA nanocomposites can be reached, showing a potential to be used in practical applications. Full article
(This article belongs to the Special Issue Recycling Polymers: The Path to a Sustainable Future)
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