Polymers for Recycling and Valorization of Soft and Hard Materials

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

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 10767

Special Issue Editors


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Guest Editor
Department of Fiber and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
Interests: polymers; recycling; upcycling; biomass; processing; absorbents; gels

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Guest Editor
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, 41012 Sevilla, Spain
Interests: biopolymers; food waste recovery; rheology; innovative processing technologies; functional foods; sustainability
Special Issues, Collections and Topics in MDPI journals
Department of Fibre and Polymer Technology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
Interests: biomolecules; water purification; photocatalyst; batteries; recycling; electrochemistry

Special Issue Information

Dear Colleagues,

Sustainability and efficient use of industrial waste as a raw material for valorization has become the utmost important step for future product development. Many industries face major challenges in complying with minimum environmental demands, while simultaneously others produce vast amounts of biobased co-products, often in the form of waste. Consequently, new research focuses on using these bio-based co-products (primarily polymers) to develop materials with functional properties, thereby reinserting them in the energy cycle with a new purpose. An advantage of using polymeric raw materials obtained from industrial streams is that they are already available in large amounts, facilitating research upscaling. Recent examples of high-potential polymers are proteins and cellulose fractions obtained from co-products of the agricultural and animal industries. The above strategy is a powerful pathway for a cradle-to-cradle sustainable approach (waste-to-product) and provides synergy in various research fields with vast bioeconomic interest.  Potential research fields where important sustainability issues are to be addressed include (but are not limited to): use of biopolymers as superabsorbents (e.g., sanitary articles), polymers as components to recycle and valorize waste materials (e.g., battery recycling), and water purification (e.g., ion-sieve).

The Special Issue, entitled “Polymers for Recycling and Valorization of Soft and Hard Materials,” would serve as a platform for pipeline research focusing on spent polymeric materials used to produce new functional and sustainable soft/hard products. The Special Issue also covers the development of products using polymers from industrial streams for maximizing resource efficiency. Research using polymers as intermediates for developing more efficient recycling methods and processes for valorizing soft and hard materials will also be considered within the Special issue.

Dr. Antonio Capezza
Dr. Víctor Manuel Pérez Puyana
Dr. Xiong Xiao
Guest Editors

Manuscript Submission Information

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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

  • sustainability
  • waste
  • biopolymers
  • recycling
  • valorization
  • bioeconomy
  • processing
  • circularity
  • cradle-to-cradle

Published Papers (5 papers)

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Research

14 pages, 3732 KiB  
Article
Stabilization and Valorization of Beer Bagasse to Obtain Bioplastics
by Daniel Castro-Criado, Johar Amin Ahmed Abdullah, Alberto Romero and Mercedes Jiménez-Rosado
Polymers 2023, 15(8), 1877; https://doi.org/10.3390/polym15081877 - 14 Apr 2023
Cited by 4 | Viewed by 2032
Abstract
Beer bagasse is a residue produced in large quantities, though it is undervalued in the industry. Its high protein and polysaccharide content make it attractive for use in sectors such as the manufacture of bioplastics. However, its high water content makes it necessary [...] Read more.
Beer bagasse is a residue produced in large quantities, though it is undervalued in the industry. Its high protein and polysaccharide content make it attractive for use in sectors such as the manufacture of bioplastics. However, its high water content makes it necessary to stabilize it before being considered as a raw material. The main objective of this work was to evaluate the stabilization of beer bagasse and the production of bioplastics from it. In this sense, different drying methods (freeze-drying and heat treatment at 45 and 105 °C) were studied. The bagasse was also characterized physicochemically to evaluate its potential. In addition, bagasse was used in combination with glycerol (plasticizer) to make bioplastics by injection molding, analyzing their mechanical properties, water absorption capacity and biodegradability. The results showed the great potential of bagasse, presenting a high content of proteins (18–20%) and polysaccharides (60–67%) after its stabilization, with freeze-drying being the most suitable method to avoid its denaturation. Bioplastics present appropriate properties for use in applications such as horticulture and agriculture. Full article
(This article belongs to the Special Issue Polymers for Recycling and Valorization of Soft and Hard Materials)
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16 pages, 2867 KiB  
Article
Developing Post-Consumer Recycled Flexible Polypropylene and Fumed Silica-Based Nanocomposites with Improved Processability and Thermal Stability
by Eliezer Velásquez, Cristian Patiño Vidal, Guillermo Copello, Carol López de Dicastillo, C. J. Pérez, Abel Guarda and María José Galotto
Polymers 2023, 15(5), 1142; https://doi.org/10.3390/polym15051142 - 24 Feb 2023
Cited by 4 | Viewed by 1827
Abstract
Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal–mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This [...] Read more.
Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal–mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This work determined the effect of incorporating two fumed nanosilica (NS) types on processability improvement of post-consumer recycled flexible polypropylene (PCPP) through ATR-FTIR, TGA, DSC, MFI and rheological analysis. Presence of trace polyethylene in the collected PCPP increased the thermal stability of the PP and was significantly maximized by NS addition. The onset decomposition temperature raised around 15 °C when 4 and 2 wt% of a non-treated and organically modified NS were used, respectively. NS acted as a nucleating agent and increased the crystallinity of the polymer, but the crystallization and melting temperatures were not affected. The processability of the nanocomposites was improved, observed as an increase in viscosity, storage and loss moduli with respect to the control PCPP, which were deteriorated due to chain scission during recycling. The highest recovery in viscosity and reduction in MFI were found for the hydrophilic NS due to a greater impact of hydrogen bond interactions between the silanol groups of this NS and the oxidized groups of the PCPP. Full article
(This article belongs to the Special Issue Polymers for Recycling and Valorization of Soft and Hard Materials)
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14 pages, 2185 KiB  
Article
Feasibility of Valorization of Post-Consumer Recycled Flexible Polypropylene by Adding Fumed Nanosilica for Its Potential Use in Food Packaging toward Sustainability
by Eliezer Velásquez, Carol López de Dicastillo, Cristian Patiño Vidal, Guillermo Copello, Cristopher Reyes, Abel Guarda and María José Galotto
Polymers 2023, 15(5), 1081; https://doi.org/10.3390/polym15051081 - 21 Feb 2023
Cited by 4 | Viewed by 1751
Abstract
The food industry has a current challenge of increasing the recycling of post-consumer plastics to reduce plastic waste towards a circular economy, especially flexible polypropylene, which is highly demanded in food packaging. However, recycling post-consumer plastics is limited because service life and reprocessing [...] Read more.
The food industry has a current challenge of increasing the recycling of post-consumer plastics to reduce plastic waste towards a circular economy, especially flexible polypropylene, which is highly demanded in food packaging. However, recycling post-consumer plastics is limited because service life and reprocessing degrade their physical-mechanical properties and modify the migration of components from the recycled material to the food. This research evaluated the feasibility of valorization of post-consumer recycled flexible polypropylene (PCPP) by incorporating fumed nanosilica (NS). For this purpose, the effect of concentration and type (hydrophilic and hydrophobic) of NS on the morphological, mechanical, sealing, barrier and overall migration properties of PCPP films was studied. Incorporating NS improved Young’s modulus and, more significantly, tensile strength at 0.5 wt% and 1 wt%, where a better particle dispersion was confirmed by EDS-SEM, but it diminished elongation at breakage of the films. Interestingly, NS tended to increase the seal strength of PCPP nanocomposite films more significantly at higher NS content, showing a seal failure of the adhesive peel type which is preferred for flexible packaging. NS at 1 wt% did not affect the water vapor and oxygen permeabilities of the films. Overall migration of PCPP and nanocomposites exceeded the limit value of 10 mg dm−2 allowed by European legislation at the studied concentrations of 1% and 4 wt%. Nonetheless, NS reduced the overall migration of PCPP from 17.3 to 15 mg dm−2 in all nanocomposites. In conclusion, PCPP with 1 wt% of hydrophobic NS presented an improved overall performance of the studied packaging properties. Full article
(This article belongs to the Special Issue Polymers for Recycling and Valorization of Soft and Hard Materials)
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16 pages, 3646 KiB  
Article
Functionalization Routes for Keratin from Poultry Industry Side-Streams—Towards Bio-Based Absorbent Polymers
by Victor M. Perez-Puyana, Antonio J. Capezza, William R. Newson, Carlos Bengoechea, Eva Johansson, Antonio Guerrero and Mikael S. Hendeqvist
Polymers 2023, 15(2), 351; https://doi.org/10.3390/polym15020351 - 9 Jan 2023
Cited by 2 | Viewed by 1698
Abstract
Keratin is a largely available protein that can be obtained from the ca. 3 million tons of feathers that the European poultry industry produces as a side-stream. Here, the functionalization of keratin from poultry feathers was evaluated using a one- versus two-stage process [...] Read more.
Keratin is a largely available protein that can be obtained from the ca. 3 million tons of feathers that the European poultry industry produces as a side-stream. Here, the functionalization of keratin from poultry feathers was evaluated using a one- versus two-stage process using two functionalization agents (succinic anhydride-SA and ethylene dianhydride-EDTAD). The functionalization resulted in the keratin having improved liquid swelling capacities, reaching up to 400%, 300%, and 85% increase in water, saline, and blood, respectively, compared to non-functionalized keratin. The highest swelling was obtained for samples functionalized with EDTAD (one-stage process), while the highest saline uptake was noted for samples processed with 25 wt% SA (two-stage process). Swelling kinetics modeling indicated that the water uptake by the functionalized samples takes place in two steps, and the EDTAD samples showed the highest diffusivity. It is demonstrated that the one-stage functionalization of keratin utilizing EDTAD results in better performance than two-stages, which allows for resource-saving and, thereby, protecting the environment. The results show some potential for the keratin to be utilized as liquid absorbent materials in water, saline, and blood uptake applications. Using keratin from side-streams is an advantage from a sustainability perspective over biomacromolecules that need to be extracted from virgin biomass. Full article
(This article belongs to the Special Issue Polymers for Recycling and Valorization of Soft and Hard Materials)
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28 pages, 8112 KiB  
Article
Characterization and Modification of Red Mud and Ferrosilicomanganese Fines and Their Application in the Synthesis of Hybrid Hydrogels
by Arnaldo Ramírez, Leonir Gómez, Alejandro J. Müller and Blanca Rojas de Gáscue
Polymers 2022, 14(20), 4330; https://doi.org/10.3390/polym14204330 - 14 Oct 2022
Cited by 1 | Viewed by 2212
Abstract
In this work, hybrid hydrogels were synthesized with the inclusion of two types of clay materials that are considered industrial waste: red mud (RM) and ferrosilicomanganese fines (FeSiMn). These solid waste materials were characterized by studying their particle size and chemical composition, which [...] Read more.
In this work, hybrid hydrogels were synthesized with the inclusion of two types of clay materials that are considered industrial waste: red mud (RM) and ferrosilicomanganese fines (FeSiMn). These solid waste materials were characterized by studying their particle size and chemical composition, which are two key variables for their application in the synthesis of hybrid hydrogels. The morphology imaged by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), showed, in the case of RM, heterogeneous size and shape particles, with 73% of the particles having lengths of less than 5 μm. On the other hand, FeSiMn had particles with a circular morphology of nanometric sizes. Regarding the synthesis of the hybrid hydrogels, it was determined that the incorporation of small percentages (0.1%) of the inorganic phases improved the capacity of the materials to absorb water (swelling indices of 1678% and 1597% for the RM and FeSiMn hydrogels, respectively) compared to the conventional polyacrylamide hydrogel (1119%). An improvement in Vickers microhardness and storage modulus (G′) was also observed: the hybrid with 10% RM presented a G′, 50 times higher than conventional hydrogel. The results show the merit of RM and FeSiMn in improving the properties of hydrogels. Full article
(This article belongs to the Special Issue Polymers for Recycling and Valorization of Soft and Hard Materials)
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