Progress in Mechanical, Thermal and Chemical Recycling Technologies for Polymer Composite Waste

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 April 2022) | Viewed by 20477

Special Issue Information

Dear Colleagues,

Polymer composite waste (PCW) is one of the current challenges and classified as a main pollutant element in our planet, and that why the research in topic taking a lot of attention from the decision makers and governments. Mechanical, thermal, and chemical processes are common practices used for treating and valorisation of this type of waste. Within this frame, this special issue has been launched to cover the advanced aspects in these processes. Also, the issue covers the environmental impact, life-cycle assessment, sorting, collection, etc. of these practices and PCW. In addition, the studies are related to refining of the obtained energy products and improve the quality of the recovered secondary raw materials and their repossessing into high-value products are very welcome.

Manuscript Submission Information

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Keywords

  • polymer composite waste valorisation
  • recycling
  • life-cycle assessment
  • mechanical, thermal, and chemical treatments
  • refining of secondary raw materials
  • energy conversion

Published Papers (5 papers)

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Research

13 pages, 1590 KiB  
Article
A New Look at the Chemical Recycling of Polypropylene: Thermal Oxidative Destruction in Aqueous Oxygen-Enriched Medium
by Vadim V. Zefirov, Igor V. Elmanovich, Andrey I. Stakhanov, Alexander A. Pavlov, Svetlana V. Stakhanova, Elena P. Kharitonova and Marat O. Gallyamov
Polymers 2022, 14(4), 744; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040744 - 15 Feb 2022
Cited by 3 | Viewed by 3147
Abstract
Recycling of plastic waste, in particular polypropylene, represents one of the most pressing challenges facing humanity. Despite the promise of chemical methods for recycling polypropylene, they usually require a high temperature and are energy-intensive. In this work, we investigated the oxidative thermolysis of [...] Read more.
Recycling of plastic waste, in particular polypropylene, represents one of the most pressing challenges facing humanity. Despite the promise of chemical methods for recycling polypropylene, they usually require a high temperature and are energy-intensive. In this work, we investigated the oxidative thermolysis of polypropylene in aqueous media. This approach rendered it possible to carry out the decomposition of the polymer at a comparatively low temperature (150 °C). It was shown that among the tested, the most promising aqueous medium for the decomposition of polypropylene is water saturated with gaseous oxygen at an elevated pressure (14 bar) and at a temperature of 150 °C. In such an environment, polypropylene was converted mostly to acetic acid (up to 1.3 g/g acetic acid to starting polypropylene mass ratio). Moreover, methanol, formic acid, and propionic acid were also detected as the products. Finally, the applicability of the proposed recycling method to real polypropylene waste was shown. Full article
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11 pages, 1652 KiB  
Article
Investigation of Polyester Tire Cord Glycolysis Accompanied by Rubber Crumb Devulcanization
by Kirill Kirshanov, Roman Toms, Pavel Melnikov and Alexander Gervald
Polymers 2022, 14(4), 684; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040684 - 11 Feb 2022
Cited by 13 | Viewed by 2918
Abstract
A new method for the recycling of a polyester tire cord under the action of oligoethylene terephthalates, bis(2-hydroxyethyl) terephthalate and ethylene glycol has been proposed. The method involves simultaneous homogeneous glycolysis of polyethylene terephthalate and devulcanization of crumb rubber. Polyester cord and glycolysates [...] Read more.
A new method for the recycling of a polyester tire cord under the action of oligoethylene terephthalates, bis(2-hydroxyethyl) terephthalate and ethylene glycol has been proposed. The method involves simultaneous homogeneous glycolysis of polyethylene terephthalate and devulcanization of crumb rubber. Polyester cord and glycolysates were characterized by FTIR spectroscopy and gel permeation chromatography (GPC). The devulcanization process was investigated by swelling-based methods. The rate of the proposed method of homogeneous glycolysis in a melt phase was proved to be higher than one of the heterogeneous glycolysis. The assumption of a more efficient devulcanization in the presence of a softener was also confirmed. The degree of devulcanization 46.07%, the apparent degree of swelling 167.4%, and the apparent swelling rate constant 0.0902 min−1 were achieved. The results indicate that the proposed method made it possible to carry out the glycolysis of the polyester cord of the tire more deeply than the known heterogeneous glycolysis with various agents, but further research is needed for industrial implementation. Full article
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6 pages, 1516 KiB  
Communication
Nanodispersions of TiO2 in Water for Removing Acrylic Films Used in Conservation
by Giulia Giuntoli, Marta Bini, Benedetta Ciuffi, Barbara Salvadori, Giovanni Baldi and Luca Rosi
Polymers 2021, 13(22), 3966; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13223966 - 17 Nov 2021
Cited by 1 | Viewed by 1287
Abstract
The influence of a nanodispersion of TiO2 in water (nanoparticle size: 40 nm, polydispersity index: 0.25), brushed on a Paraloid film and subjected to UV–Vis irradiation was evaluated. The TiO2 nanodispersions showed a tendency to reduce the molecular weight of Paraloid [...] Read more.
The influence of a nanodispersion of TiO2 in water (nanoparticle size: 40 nm, polydispersity index: 0.25), brushed on a Paraloid film and subjected to UV–Vis irradiation was evaluated. The TiO2 nanodispersions showed a tendency to reduce the molecular weight of Paraloid due to its photocatalytic properties. FTIR and GPC analyses and SEM images suggested the degradation of the polymer, while chromatic variations of the films were scarcely detected. This study is very remarkable in the perspective of using this material for the removal of polymeric films used in conservation. Full article
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14 pages, 2891 KiB  
Article
Life-Cycle Assessment of Polypropylene Production in the Gulf Cooperation Council (GCC) Region
by Amzan Alsabri, Furqan Tahir and Sami G. Al-Ghamdi
Polymers 2021, 13(21), 3793; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13213793 - 02 Nov 2021
Cited by 28 | Viewed by 9235
Abstract
The environmental impacts of the polypropylene (PP) manufacturing process are not fully understood in the Gulf Cooperation Council (GCC) region. There is a growing interest in assessing the environmental impacts of this highly demanded product, especially for the petrochemical industry sector. This research [...] Read more.
The environmental impacts of the polypropylene (PP) manufacturing process are not fully understood in the Gulf Cooperation Council (GCC) region. There is a growing interest in assessing the environmental impacts of this highly demanded product, especially for the petrochemical industry sector. This research examines the environmental impacts of the polypropylene manufacturing process using a life cycle assessment (LCA) approach. Gabi software is selected to carry out this research study and quantify the risks associated with manufacturing one ton of polypropylene, chosen as the functional unit for this LCA study. This work has the following merits: (i) an evaluation of environmental impacts specific to GCC region based on actual plant data; (ii) the results in this work can be used to evaluate LCA impacts of PP based products; and (iii) emphasizing the importance of waste management in reducing environmental impacts. This study shows that the polypropylene manufacturing process releases numerous pollutants into the environment, as the gross CO2 emissions for the manufacturing process of PP in the plant located in the GCC region were estimated to be 1.58 kg CO2 eq./kg-PP. The manufacturing process of propylene has extremely high impacts on global warming potential, fossil resource depletion (1.722 kg Oil eq./kg-PP), human toxicity (0.077 kg 1,4-DB eq./kg-PP), acidification (0.0049 kg SO2 eq./kg-PP), and petrochemical oxidant formation (0.0042 kg NMVOC/kg-PP). Additionally, based on the results of this present research, this study proposes possible improvements and alternative solutions such as applying advanced technologies, clean energy, and safe recycling processes in the GCC that are environmentally friendly. Full article
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18 pages, 38445 KiB  
Article
Pyrolysis Kinetic Behaviour of Glass Fibre-Reinforced Epoxy Resin Composites Using Linear and Nonlinear Isoconversional Methods
by Samy Yousef, Justas Eimontas, Nerijus Striūgas, Marius Praspaliauskas and Mohammed Ali Abdelnaby
Polymers 2021, 13(10), 1543; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13101543 - 11 May 2021
Cited by 36 | Viewed by 3113
Abstract
Due to the increasing demand for glass fibre-reinforced epoxy resin composites (GFRC), huge amounts of GFRC waste are produced annually in different sizes and shapes, which may affect its thermal and chemical decomposition using pyrolysis technology. In this context, this research aims to [...] Read more.
Due to the increasing demand for glass fibre-reinforced epoxy resin composites (GFRC), huge amounts of GFRC waste are produced annually in different sizes and shapes, which may affect its thermal and chemical decomposition using pyrolysis technology. In this context, this research aims to study the effect of mechanical pre-treatment on the pyrolysis behaviour of GFRC and its pyrolysis kinetic. The experiments were started with the fabrication of GFRC panels using the vacuum-assisted resin transfer method followed by crushing the prepared panels using ball milling, thus preparing the milled GFRC with uniform shape and size. The elemental, proximate, and morphology properties of the panels and milled GFRC were studied. The thermal and chemical decomposition of the milled GFRC was studied using thermogravimetric coupled with Fourier-transform infrared spectroscopy (TG-FTIR) at different heating rates. Meanwhile, the volatile products were examined using TG coupled with gas chromatography–mass spectrometry (GC-MS). The TG-FTIR and TG-GC-MS experiments were performed separately. Linear (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Friedman) and nonlinear (Vyazovkin and Cai) isoconversional methods were used to determine the pyrolysis kinetic of the milled GFRC based on thermogravimetry and differential thermal gravimetry (TG/DTG). In addition, the TG/DTG data of the milled GFRC were fitting using the distributed activation energy model and the independent parallel reactions kinetic model. The TG results showed that GFRC can decompose in three stages, and the main decomposition is located in the range 256–500 °C. On the other hand, aromatic benzene and a C-H bond were the major functional groups in the released volatile components in FTIR spectra, while phenol (27%), phenol,4-(1-methylethyl) (40%), and p-isopropenylphenol (34%) were the major compounds in GC-MS analysis. Whereas, the kinetic results showed that both isoconversional methods can be used to determine activation energies, which were estimated 165 KJ/mol (KAS), 193 KJ/mol (FWO), 180 KJ/mol (Friedman), 177 KJ/mol (Vyazovkin), and 174 KJ/mol (Cai). Full article
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