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Polymers
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Polymer Recycling: Degradation, Processing, Applications II
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Polymer Recycling: Degradation, Processing, Applications II

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Circular and Green Polymer Science".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 16675

Special Issue Editors

Prof. Dr. Francesco Paolo La Mantia

E-Mail Website1 Website2
Guest Editor
Department of Engineering, University of Palermo, RU INSTM, Viale delle Scienze, 90128 Palermo, Italy
Interests: polymer processing; mechanical behaviour of polymer-based systems; rheological behaviour of polymer-based systems; green composites; biocomposites; nanocomposites; biodegradable polymers; polymer blends; degradation and recycling of polymer-based systems
Special Issues, Collections and Topics in MDPI journals
Dr. Maria Chiara Mistretta

E-Mail Website
Guest Editor
Department of Engineering, RU INSTM of Palermo, University of Palermo, Viale delle Scienze ed.6, 90128 Palermo, Italy
Interests: nanocomposites; biopolymers; degradation; photooxidation; recycling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The environmental concerns regarding the final fate of polymer objects are a very important challenge for the plastic industry. Among the different strategies for decreasing or eliminating the presence of plastic waste in the environment and decreasing the amount of plastic coming from oil, recycling is one of the most important tools. Indeed, recycling can realize the recovery of the same polymer for use as a secondary material, the recovery of the monomer for use in producing new virgin polymers, the recovery of energy, and the use of the post-consumer plastic as fillers in other materials (concrete, bitumen, etc.).

As for mechanical recycling, the main problems are related to degradation during the lifetime and reprocessing operations, the loss of the properties of the secondary material, and the reprocessing of mixed plastics.

This Special Issue will follow the life of post-consumer plastics from reprocessing operations to applications. Papers on thermomechanical degradation, reprocessing, applications, chemical recycling, energy recovery, and mixed plastics are welcome.

Prof. Dr. Francesco Paolo La Mantia
Dr. Maria Chiara Mistretta
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
  • degradation
  • plastics
  • reprocessing
  • energy recovery

Related Special Issue

Published Papers (5 papers)

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Research

16 pages, 1967 KiB  
Article
Energy Recovery and Economic Evaluation for Industrial Fuel from Plastic Waste
by Ahmed Rida Galaly and Nagia Dawood
Polymers 2023, 15(11), 2433; https://doi.org/10.3390/polym15112433 - 24 May 2023
Cited by 1 | Viewed by 1742
Abstract
Plasma gasification is considered an environmentally friendly process to convert plastic waste into fuel oil; a prototype system is described to test and validate the plasma treatment of plastic waste as a strategic vision. The proposed plasma treatment project will deal with a [...] Read more.
Plasma gasification is considered an environmentally friendly process to convert plastic waste into fuel oil; a prototype system is described to test and validate the plasma treatment of plastic waste as a strategic vision. The proposed plasma treatment project will deal with a plasma reactor with a waste capacity of 200 t/day. The annual plastic waste production in tons in all regions of Makkah city during 27 years for all months in the years 1994 to 2022 is evaluated. A statistics survey of plastic waste displays the average rate generation ranging from 224 thousand tons in the year 1994 to 400 thousand tons in the year 2022, with an amount of recovered pyrolysis oil; 3.17 × 105 t with the equivalent energy; 12.55 × 109 MJ, and an amount of recovered diesel oil; 2.7 × 105 t with an amount of electricity for sale 2.96 × 106 MW.h. The economic vision will be estimated, using the results of energy generated from diesel oil as an industrial fuel extracted from plastic waste equivalent to 0.2 million barrels of diesel oil, with sales revenue and cash recovery of USD 5 million, considering the sale of each one barrel of diesel extracted from plastic waste in the range of USD 25. It is important to consider that the equivalent barrels of petroleum cost, according to the organization of the petroleum-exporting countries’ basket prices, up to USD 20 million. The sales profit (2022) is as follows: for diesel with a sales revenue of diesel oil, USD 5 million, with a rate of return of 4.1%, and a payback period of 3.75 years. The generated electricity reached USD 32 million for households and USD 50 million for factories. Full article
(This article belongs to the Special Issue Polymer Recycling: Degradation, Processing, Applications II)
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10 pages, 3746 KiB  
Article
Influence of Different Environments and Temperatures on the Photo-Oxidation Behaviour of the Polypropylene
by Francesco Paolo La Mantia, Marilena Baiamonte, Stefania Santangelo, Roberto Scaffaro and Maria Chiara Mistretta
Polymers 2023, 15(1), 74; https://doi.org/10.3390/polym15010074 - 24 Dec 2022
Cited by 4 | Viewed by 1559
Abstract
The photo-oxidation of polypropylene at two different temperatures and in three different environments—air, distilled water and sea water—has been followed as a function of the irradiation time. The photo-oxidation kinetic is dramatically dependent on the amount of oxygen available for the oxidation reactions [...] Read more.
The photo-oxidation of polypropylene at two different temperatures and in three different environments—air, distilled water and sea water—has been followed as a function of the irradiation time. The photo-oxidation kinetic is dramatically dependent on the amount of oxygen available for the oxidation reactions and on the temperature. While the photo-oxidation is very fast in air, the degradation is much slower in the two aqueous media. The degradation in sea water is slightly slower than in distilled water. In all cases, the degradation kinetic increases remarkably with the temperature. This behavior has been attributed to the lower oxygen availability for the oxidation reactions of the polymers. The light difference of the degradation kinetic between the two aqueous media depends on the small difference of the oxygen concentration at the test temperatures of 40 and 70 °C. At the latter temperature, the difference between the degradation kinetic in distilled water and sea water is still less important because increasing the temperature decreases the solubility of the oxygen, and it tends to became very similar in both samples of water. Full article
(This article belongs to the Special Issue Polymer Recycling: Degradation, Processing, Applications II)
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12 pages, 4245 KiB  
Article
Tuning the Morphology of HDPE/PP/PET Ternary Blends by Nanoparticles: A Simple Way to Improve the Performance of Mixed Recycled Plastics
by Angela Marotta, Andrea Causa, Martina Salzano de Luna, Veronica Ambrogi and Giovanni Filippone
Polymers 2022, 14(24), 5390; https://doi.org/10.3390/polym14245390 - 09 Dec 2022
Cited by 8 | Viewed by 1760
Abstract
Due to a very low mixing entropy, most of the polymer pairs are immiscible. As a result, mixing polymers of different natures in a typical mechanical recycling process leads to materials with multiple interfaces and scarce interfacial adhesion and, consequently, with unacceptably low [...] Read more.
Due to a very low mixing entropy, most of the polymer pairs are immiscible. As a result, mixing polymers of different natures in a typical mechanical recycling process leads to materials with multiple interfaces and scarce interfacial adhesion and, consequently, with unacceptably low mechanical properties. Adding nanoparticles to multiphase polymeric matrices represents a viable route to mitigate this drawback of recycled plastics. Here, we use low amounts of organo-modified clay (Cloisite® 15A) to improve the performance of a ternary blend made of high-density polyethylene (HDPE), polypropylene (PP), and polyethylene terephtalate (PET). Rather than looking for the inherent reinforcing action of the nanofiller, this goal is pursued by using nanoparticles as a clever means to manipulate the micro-scale arrangement of the polymer phases. Starting from theoretical calculations, we obtained a radical change in the blend microstructure upon the addition of only 2-wt.% of nanoclay, with the obtaining of a finer morphology with an intimate interpenetration of the polymeric phases. Rather than on flexural and impact properties, this microstructure, deliberately promoted by nanoparticles, led to a substantial increase (>50 °C) of a softening temperature conventionally defined from dynamic-mechanical measurements. Full article
(This article belongs to the Special Issue Polymer Recycling: Degradation, Processing, Applications II)
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17 pages, 4689 KiB  
Article
Evaluation of Novel Compatibility Strategies for Improving the Performance of Recycled Low-Density Polyethylene Based Biocomposites
by Mahmoud M. A. Nassar and Ishaq Sider
Polymers 2021, 13(20), 3486; https://doi.org/10.3390/polym13203486 - 11 Oct 2021
Cited by 6 | Viewed by 1856
Abstract
The interfacial compatibility of the natural filler and synthetic polymer is the key performance characteristic of biocomposites. The fillers are chemically modified, or coupling agents and compatibilisers are used to ensure optimal filler-polymer compatibility. Hence, we have investigated the effect of compatibilisation strategies [...] Read more.
The interfacial compatibility of the natural filler and synthetic polymer is the key performance characteristic of biocomposites. The fillers are chemically modified, or coupling agents and compatibilisers are used to ensure optimal filler-polymer compatibility. Hence, we have investigated the effect of compatibilisation strategies of olive pits (OP) flour content (10, 20, 30, and 40%wt.) filled with recycled low-density polyethylene (rLDPE) on the chemical, physical, mechanical, and thermal behaviour of the developed biocomposites. In this study, we aim to investigate the filler-polymer compatibility in biocomposites by employing novel strategies for the functionalisation of OP filler and/or rLDPE matrix. Specifically, four cases are considered: untreated OP filled rLDPE (Case 1), treated OP filled rLDPE (Case 2), treated OP filled functionalised rLDPE (Case 3), and treated and functionalised OP filled functionalised rLDPE (Case 4). In general, the evaluation of the performance of biocomposites facilitated the application of OP industrial waste as an eco-friendly reinforcing agent for rLDPE-based biocomposites. Furthermore, surface treatment and compatibilisation improved the properties of the developed biocomposites over untreated filler or uncoupled biocomposites. Besides that, the compatibilisers used aided in reducing water uptake and improving thermal behaviour, which contributed to the stability of the manufactured biocomposites. Full article
(This article belongs to the Special Issue Polymer Recycling: Degradation, Processing, Applications II)
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23 pages, 56327 KiB  
Article
Characterization of Composition and Structure–Property Relationships of Commercial Post-Consumer Polyethylene and Polypropylene Recyclates
by Markus Gall, Paul J. Freudenthaler, Joerg Fischer and Reinhold W. Lang
Polymers 2021, 13(10), 1574; https://doi.org/10.3390/polym13101574 - 14 May 2021
Cited by 43 | Viewed by 8685
Abstract
The current efforts in moving closer towards a circular plastics economy puts massive pressure on recycled plastics, especially recycled polyethylene (rPE) and recycled polypropylene (rPP) to enter new markets. Their market penetration remained low so far, despite PE and PP constituting the largest [...] Read more.
The current efforts in moving closer towards a circular plastics economy puts massive pressure on recycled plastics, especially recycled polyethylene (rPE) and recycled polypropylene (rPP) to enter new markets. Their market penetration remained low so far, despite PE and PP constituting the largest share of plastic wastes. However, with the current imperative of more circularity comes a new focus on performance of recyclates. Hence, a detailed understanding of composition and structure–property relationships of post-consumer recyclates has to be developed. Five recycling companies from the Austrian and German markets were asked to supply their purest high-quality rPE and rPP grades. These were characterized by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy, and micro-imaging. Technological characterization included density measurements, determination of the melt flow rate (MFR), and Charpy impact testing. All recyclates contained diverse contaminants and inclusions ranging from legacy fillers like calcium carbonate to polymeric contaminants like polyamides or polyolefin cross-contamination. The overall amount, size, and distribution of contaminants varied significantly among suppliers. Furthermore, first structure–property relationships for polyolefin recyclates that link inorganic content and polymeric purity with density and impact performance could be derived. Full article
(This article belongs to the Special Issue Polymer Recycling: Degradation, Processing, Applications II)
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