System for Polymers Recycling and Circular Economy

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 (30 June 2023) | Viewed by 6288

Special Issue Editors

Special Issue Information

Dear Colleagues,

During their “lifetime”, polymers undergo various degradative effects due to the surrounding environment.

As part of a circular economy, mechanical and chemical recycling is one of the possible ways to enhance the value of postconsumer plastic materials. However, the final performance of the recycled material will mainly depend on the final properties of the postconsumer materials and on the system for recycling.

Therefore, it is important to optimize the recycling operation in order to avoid a drastic decrease in mechanical properties and processability.

Prof. Dr. Roberto Scaffaro
Dr. Maria Chiara Mistretta
Guest Editors

Manuscript Submission Information

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Keywords

  • polymers
  • recycling
  • degradation
  • postconsumer materials
  • recycled materials
  • circular economy

Published Papers (3 papers)

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Research

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10 pages, 2968 KiB  
Article
Comparison of the Recycling Behavior of a Polypropylene Sample Aged in Air and in Marine Water
by Francesco Paolo La Mantia, Roberto Scaffaro, Marilena Baiamonte, Manuela Ceraulo and Maria Chiara Mistretta
Polymers 2023, 15(9), 2173; https://doi.org/10.3390/polym15092173 - 03 May 2023
Cited by 4 | Viewed by 999
Abstract
During the processing and during their lifetime, polymers are subjected to several environmental stresses—thermomechanical, photo-oxidative, etc.—that can strongly modify their chemical and molecular structure and, consequently, their morphology. Reduction of the molecular weight and formation of double bonds and oxygenated groups are the [...] Read more.
During the processing and during their lifetime, polymers are subjected to several environmental stresses—thermomechanical, photo-oxidative, etc.—that can strongly modify their chemical and molecular structure and, consequently, their morphology. Reduction of the molecular weight and formation of double bonds and oxygenated groups are the main changes observed as a consequence of the degradation. As a result of these changes, the macroscopic properties are dramatically modified. These changes can have a relevant effect if the post-consumer plastic manufacts are recycled. In this work, a sample of polypropylene subjected to two different degradation histories—photo-oxidation in air and in marine water—is reprocessed two times in a mini twin-screw extruder in the same processing conditions. The effect of the thermomechanical degradation during the reprocessing is different. Indeed, the less severe degraded sample shows a higher degradation level during reprocessing because the shear stress is larger. This means that the thermomechanical degradation kinetics is larger in the less degraded samples. Nevertheless, the final properties of the recycled polymers are different because the properties of the photo-oxidized samples before reprocessing were very different. Full article
(This article belongs to the Special Issue System for Polymers Recycling and Circular Economy)
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12 pages, 1681 KiB  
Article
Dyeing Non-Recyclable Polyethylene Plastic with Photoacid Phycocyanobilin from Spirulina Algae: Ultrafast Photoluminescence Studies
by Maryam Alhefeiti, Falguni Chandra, Ravindra Kumar Gupta and Na’il Saleh
Polymers 2022, 14(22), 4811; https://doi.org/10.3390/polym14224811 - 09 Nov 2022
Cited by 1 | Viewed by 1491
Abstract
Despite the enormous environmental damage caused by plastic waste, it makes up over one-third of globally produced plastics. Polyethylene (PE) wastes have low recycling but high production rates. Towards the construction of ionic solar cells from PE, the present work describes the loading [...] Read more.
Despite the enormous environmental damage caused by plastic waste, it makes up over one-third of globally produced plastics. Polyethylene (PE) wastes have low recycling but high production rates. Towards the construction of ionic solar cells from PE, the present work describes the loading of a bioactive photoacid phycocyanobilin (PCB) dye from the pigment of Spirulina blue–green algae (as a natural resource) on low-density polyethylene (LDPE) plastic film. Dyeing was confirmed by X-ray photoelectron spectroscopy (XPS). Upon excitation of the Soret-band (400 nm), the photoluminescence (PL) spectra of PCB in neat solvents revealed two prominent emission peaks at 450–550 and 600–700 nm. The first band assigned to bilirubin-like (PCBBR) species predominated the spectral profile in the highly rigid solvent glycerol and upon loading 0.45 % (w/w) of the dye on plastic. The photoluminescence excitation (PLE) spectra of PCB for the second region (Q-band) at 672 nm in the same solvents confirmed the ground state heterogenicity previously associated with the presence of PCBA (neutral), PCBB (cationic), and PCBC (anionic) conformers. Time-resolved photoluminescence (TRPL) measurements induced via excitation of all PCB species at 510 nm in methanol revealed three-lifetime components with τ1 = ~0.1 ns and τ2 = ~2 ns associated with PCBBR species and τ3 = ~5 ns pertinent to the long-living photoproduct X*. Decay-associated spectra (DAS) analysis of the photoluminescence transient spectra of the final dyed films in the solid-state confirmed the improved generation of the long-living photoproduct as manifested in a significant increase in the PL intensity (~100-fold) and lifetime value (~90 ns) in the Q-region upon loading 6.92 % (w/w) of the dye on plastic. The photoproduct species were presumably assigned to the deprotonated PCB species, suggesting improved ionic mobility. The potential implementation of the PCB-sensitized PE solid wastes for the fabrication of ionic solar cells is discussed. Full article
(This article belongs to the Special Issue System for Polymers Recycling and Circular Economy)
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Review

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32 pages, 4130 KiB  
Review
Colombian Sustainability Perspective on Fused Deposition Modeling Technology: Opportunity to Develop Recycled and Biobased 3D Printing Filaments
by Maria A. Morales, Alejandro Maranon, Camilo Hernandez, Veronique Michaud and Alicia Porras
Polymers 2023, 15(3), 528; https://doi.org/10.3390/polym15030528 - 19 Jan 2023
Cited by 10 | Viewed by 3291
Abstract
In the context of the preservation of natural resources, researchers show a growing interest in developing eco—friendly materials based on recycled polymers and natural fiber biocomposites to minimize plastic and agroindustrial waste pollution. The development of new materials must be integrated within the [...] Read more.
In the context of the preservation of natural resources, researchers show a growing interest in developing eco—friendly materials based on recycled polymers and natural fiber biocomposites to minimize plastic and agroindustrial waste pollution. The development of new materials must be integrated within the circular economy concepts to guarantee sustainable production. In parallel, fused deposition modeling, an additive manufacturing technology, provides the opportunity to use these new materials in an efficient and sustainable manner. This review presents the context of plastics and agro-industrial fiber pollution, followed by the opportunity to give them added value by applying circular economy concepts and implementing these residues to develop new materials for the manufacture of fused deposition modeling 3D printing technique feedstock. Colombian perspective is highlighted since 3D printing technology is growing there, and Colombian biodiversity represents a high reservoir of materials. Also, recycling in Colombia promotes compliance with the 2030 Agenda and the Sustainable Development Goals. Full article
(This article belongs to the Special Issue System for Polymers Recycling and Circular Economy)
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