Manufacturing and Processing of Recycled Plastics

A special issue of Journal of Manufacturing and Materials Processing (ISSN 2504-4494).

Deadline for manuscript submissions: closed (1 September 2023) | Viewed by 12965

Special Issue Editor


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Guest Editor
Centre for Mechanical Technology & Automation, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: additive manufacturing; circular economy; eco-design and eco-efficiency; Industry 4.0; manufacturing processes; nanotechnology; product development; thermoplastics processing; thermoplastics recycling

Special Issue Information

Dear colleagues,

The solution to the increasing levels of global plastic pollution, whether on land or the oceans, is the development of proper processes of incorporating recycled plastics into added-value products, which will turn plastic waste into an asset. Although plastic waste end-of-life treatment possibilities are still presently quite limited, costly, and time-intensive, it is important to continue with the effort to allow recycled plastics to be more promptly taken as raw material for new products. For the latter, there is a need for reliable and standardized procedures to characterize, trace, and guarantee the safety of recyclates, as well as the diffusion of successful processing of recycled plastics case studies.

In this Special Issue of JMMP, current research findings are going to be reported which focus on processes, equipment, systems, and material evaluation that can contribute to the development of robust and easy-to-use sampling and analysis procedures to ensure consistent recyclate quality and safe products, methodologies to establish the degree of degradation of recycled materials and to foresee their end-of-life, simulation of the processing of the recyclate, and recycled-based products.

In line with the scope of JMMP, we are interested in contributions that focus on topics such as:

  • Recycled plastic processing technologies;
  • Characterization techniques and methodologies to assess recycled plastic as raw material, as well as the evaluation of recycled plastic produced products for service;
  • End-of-life analysis and treatment;
  • Processing simulation, mechanics analysis, and predictive modeling of recycled-based products.

Dr. Victor Neto
Guest Editor

Manuscript Submission Information

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Keywords

  • recycled plastics
  • recycled plastics-based products
  • processing
  • assessment
  • circular economy

Published Papers (4 papers)

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Research

22 pages, 2208 KiB  
Article
Extending the Operating Life of Thermoplastic Components via On-Demand Patching and Repair Using Fused Filament Fabrication
by Charul Chadha, Kai James, Iwona M. Jasiuk and Albert E. Patterson
J. Manuf. Mater. Process. 2022, 6(5), 103; https://doi.org/10.3390/jmmp6050103 - 16 Sep 2022
Cited by 4 | Viewed by 2220
Abstract
Polymer-based engineering materials (plastics, polymer matrix composites, and similar) are becoming more widely used for the design and construction of consumer products and systems. While providing a host of design benefits, these materials also can have a large detrimental effect on the environment [...] Read more.
Polymer-based engineering materials (plastics, polymer matrix composites, and similar) are becoming more widely used for the design and construction of consumer products and systems. While providing a host of design benefits, these materials also can have a large detrimental effect on the environment when not handled properly. One of the best ways to increase the sustainability of systems created using these materials is to extend their operating life as much as possible. Additive manufacturing (AM) technologies offer a powerful tool for this, as they allow easy repair of damaged or worn components in an automated or semi-automated way. This article explores the use of the fused filament fabrication (FFF) process as a tool for repairing high-value (i.e., difficult or expensive to replace) thermoplastic parts. The major design opportunities and restrictions are presented, as well as an evaluation of the types of repair jobs for which this process could be suitable and effective. Advice and ideas for future implementations and improvements are provided as well. A detailed case study is presented, where cracked ABS bars were repaired using FFF-deposited patches while varying the print parameters using a factorial designed experiment. The repaired bars were tested against the baseline and in most cases were found to be as good as or better than the original bars under a bending load. This case study demonstrates the concepts and explores how this repair approach could be realistically employed in practice. Full article
(This article belongs to the Special Issue Manufacturing and Processing of Recycled Plastics)
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15 pages, 5628 KiB  
Article
Processability and Physical Properties of Compatibilized Recycled HDPE/Rice Husk Biocomposites
by Andrés Rigail-Cedeño, Miriam Lazo, Julio Gaona, Joshua Delgado, Clotario V. Tapia-Bastidas, Ana L. Rivas, Estephany Adrián and Rodrigo Perugachi
J. Manuf. Mater. Process. 2022, 6(4), 67; https://doi.org/10.3390/jmmp6040067 - 23 Jun 2022
Cited by 6 | Viewed by 2921
Abstract
The circular economy promotes plastic recycling, waste minimization, and sustainable materials. Hence, the use of agricultural waste and recycled plastics is an eco-friendly and economic outlook for developing eco-designed products. Moreover, new alternatives to reinforce recycled polyolefins and add value to agroindustrial byproducts [...] Read more.
The circular economy promotes plastic recycling, waste minimization, and sustainable materials. Hence, the use of agricultural waste and recycled plastics is an eco-friendly and economic outlook for developing eco-designed products. Moreover, new alternatives to reinforce recycled polyolefins and add value to agroindustrial byproducts are emerging to develop processable materials with reliable performance for industrial applications. In this study, post-consumer recycled high-density polyethylene (rHDPE) and ground rice husk (RH) of 20% w/w were blended in a torque rheometer with or without the following coupling agents: (i) maleic anhydride grafted polymer (MAEO) 5% w/w, (ii) neoalkoxy titanate (NAT) 1.5% w/w, and (iii) ethylene–glycidyl methacrylate copolymer (EGMA) 5% w/w. In terms of processability, the addition of RH decreased the specific energy consumption in the torque experiments with or without additives compared to neat rHDPE. Furthermore, the time to reach thermal stability in the extrusion process was improved with EGMA and MAEO compatibilizers. Tensile and impact test results showed that using coupling agents enhanced the properties of the RH composites. On the other hand, thermal properties analyzed through differential scanning calorimetry and thermogravimetric analysis showed no significant variation for all composites. The morphology of the tensile fracture surfaces was observed via scanning electron microscopy. The results show that these recycled composites are feasible for manufacturing products when an appropriate compatibilizer is used. Full article
(This article belongs to the Special Issue Manufacturing and Processing of Recycled Plastics)
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17 pages, 5600 KiB  
Article
Comparative Analysis of the Solid Conveying of Regrind, Virgin and Powdery Polyolefins in Single-Screw Extrusion
by Kai S. Johann, Adrian Reißing and Christian Bonten
J. Manuf. Mater. Process. 2022, 6(3), 56; https://doi.org/10.3390/jmmp6030056 - 24 May 2022
Cited by 3 | Viewed by 2784
Abstract
The shape and size of processed materials play a crucial role in the solid conveying characteristics of single-screw extruders. Thus, the increasing amount of plastic regrind leads to new challenges in screw extrusion. This work investigates the conveying behavior of three distinctly different [...] Read more.
The shape and size of processed materials play a crucial role in the solid conveying characteristics of single-screw extruders. Thus, the increasing amount of plastic regrind leads to new challenges in screw extrusion. This work investigates the conveying behavior of three distinctly different material shapes in an axially as well as a helically grooved solid conveying zone. A uniform virgin polypropylene (PP) granule, an irregularly plate-shaped PP regrind and a powdery polyethylene (PE) are processed at screw speeds up to 1350 rpm. Thereby, frictionally engaged conveying in the grooves is visualized for the utilized powder. Similarly, the virgin granule is subject to forced conveying by interlocking in the grooves. The experimentally determined throughput is furthermore compared to analytical calculations which assume a so-called nut–screw conveying. It is found that these calculations perfectly predict the throughput when processing the virgin granule and the powder in a helically grooved barrel. In contrast, the analytical calculation significantly underestimates the throughput for the regrind. This underestimation is expected to be mainly caused by its plate shape and a difference in bulk density. The actual bulk density in the extruder is probably significantly higher due to both orientation and compaction effects compared to the measured bulk density that is used for the analytical calculation. Additionally, the regrind exhibits a fluctuating throughput due to the non-constant bulk density, which results from an irregular regrind shape and a broad size distribution. Full article
(This article belongs to the Special Issue Manufacturing and Processing of Recycled Plastics)
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20 pages, 11242 KiB  
Article
Reprocessability of PLA through Chain Extension for Fused Filament Fabrication
by Carlos Correia, Tiago E. P. Gomes, Idalina Gonçalves and Victor Neto
J. Manuf. Mater. Process. 2022, 6(1), 26; https://doi.org/10.3390/jmmp6010026 - 19 Feb 2022
Cited by 11 | Viewed by 3595
Abstract
As additive manufacturing (AM) technologies have been gaining popularity in the plastic processing sector, it has become a major concern to establish closed-loop recycling strategies to maximize the value of the materials processed, therefore enhancing their sustainability. However, there are challenges to overcome [...] Read more.
As additive manufacturing (AM) technologies have been gaining popularity in the plastic processing sector, it has become a major concern to establish closed-loop recycling strategies to maximize the value of the materials processed, therefore enhancing their sustainability. However, there are challenges to overcome related to the performance of recycled materials since, after mechanical recycling, the molecular degradation of thermoplastics shifts their performance and processability. In this work, it was hypothesized that the incorporation of a chain extender (CE) during the reprocessing would allow us to overcome these drawbacks. To attest this conjecture, the influence of 1,3-Bis(4,5-dihydro-2-oxazolyl)benzene (PBO), used as a CE, on mechanical, thermal, and rheological properties of polilactic acid (PLA) was studied. Furthermore, a closed-loop recycling system based on Fused Filament Fabrication (FFF) was attempted, consisting of the material preparation, filament extrusion, production of 3D components, and mechanical recycling steps. PBO partially recovered the recycled PLA mechanical performance, reflected by an increase in both tensile modulus (+13%) and tensile strength (+121%), when compared with recycled PLA without PBO. Printability tests were conducted, with the material’s brittle behavior being the major constraint for successfully establishing a closed-loop recycling scheme for FFF applications. Full article
(This article belongs to the Special Issue Manufacturing and Processing of Recycled Plastics)
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