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Degradation and Stabilization of Polymer Materials

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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 (25 August 2023) | Viewed by 24553

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Dr. Branka Mušič

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Guest Editor

Slovenian National Building and Civil Engineering Institute, 1000 Ljubljana, Slovenia
Interests: polymers, composite materials; accelerated ageing; physical, chemical, mechanical, thermal, morphological, analysis; renewable resources and circular economy
Special Issues, Collections and Topics in MDPI journals

Dr. Andrijana Sever Škapin

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Guest Editor

Slovenian National Building and Civil Engineering Institute, Dimičeva 12, 1000 Ljubljana, Slovenia
Interests: polymers; nanomaterials; durability; microstructure; microplastics; consolidation; photocatalysis; cultural heritage
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymer science and technology is one of the most important areas for the EU scientific community and economy, since the polymer industry directly employs 1.5 million people, and turnover in 2019 was more than 350 billion euros. EU polymer production was about 57.9 million tonnes that year, without polymer fibers. Despite the fact that we should first and foremost prevent the possibility of plastics ending up in the environment, in such huge production of plastic products we always find various plastic products discarded in environment. There, it begins to degradate into microplastics and even nanoplastics, which, however, have different effects on the environment and living organisms. It is therefore important that all the potential impacts of micro and nanoplastics on the ecosystem are studied, thus encouraging scientists to do new research and making the general public aware of their negative consequences if they accumulate in the environment. In this special issue, we'll be very glad to include works made by the authors, working on research efforts and advances in the field of polymeric micro- and nanoparticles, their degradation processes in the environment supported by comprehensive characterisation and their impact on ecosystem. Original papers, reviews or communications for this Special Issue are welcome.

Dr. Branka Mušič
Dr. Andrijana Sever Škapin
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-based materials
-nano, -micro, -macro composites
Effects on (micro) organisms and toxicity
Impact on the ecosystem
Mechanism and products of accelerated aging and degradation
Physical, chemical, mechanical, thermal, morphological, analysis
Biodegradability, sustainability, life cycle
Renewable and recycled resources and the circular economy

Published Papers (11 papers)

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Editorial

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7 pages, 223 KiB

Open AccessEditorial

Degradation and Stabilization of Polymer Materials

by Branka Mušič and Andrijana Sever Škapin

Polymers 2023, 15(23), 4519; https://doi.org/10.3390/polym15234519 - 24 Nov 2023

Viewed by 1485

Abstract

The growing awareness of the consequences of climate change has prompted the formulation of policies and regulations to foster sustainability [...] Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

Research

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17 pages, 8876 KiB

Open AccessArticle

Degradation and Lifetime Prediction of Epoxy Composite Insulation Materials under High Relative Humidity

by Jielin Ma, Yan Yang, Qi Wang, Yuheng Deng, Malvern Yap, Wen Kwang Chern, Joo Tien Oh and Zhong Chen

Polymers 2023, 15(12), 2666; https://doi.org/10.3390/polym15122666 - 13 Jun 2023

Cited by 1 | Viewed by 1889

Abstract

Insulation failure of composite epoxy insulation materials in distribution switchgear under the stress of heat and humidity is one of the leading causes of damage to switchgear components. This work prepared composite epoxy insulation materials by casting and curing a diglycidyl ether of bisphenol A (DGEBA)/anhydride/wollastonite composite system, and performed material accelerated aging experiments under three conditions: 75 °C and 95% relative humidity (RH), 85 °C and 95% RH, and 95 °C and 95% RH. Material, mechanical, thermal, chemical, and microstructural properties were investigated. Based on the IEC 60216-2 standard and our data, tensile strength and ester carbonyl bond (C=O) absorption in infrared spectra were chosen as failure criteria. At the failure points, the ester C=O absorption decreased to ~28% and the tensile strength decreased to 50%. Accordingly, a lifetime prediction model was established to estimate material lifetime at 25 °C and 95% RH to be 33.16 years. The material degradation mechanism was attributed to the hydrolysis of epoxy resin ester bonds into organic acids and alcohols under heat and humidity stresses. Organic acids reacted with calcium ions (Ca²⁺) of fillers to form carboxylate, which destroyed the resin-filler interface, resulting in a hydrophilic surface and a decrease in mechanical strength. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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13 pages, 2029 KiB

Open AccessArticle

Novel Environmentally Friendly Covalent Organic Framework/Polylactic Acid Composite Material with High Chemical Stability for Sand-Control Material

by Wanjia Yang, Yongling Du and Benli Liu

Polymers 2023, 15(7), 1659; https://doi.org/10.3390/polym15071659 - 27 Mar 2023

Cited by 1 | Viewed by 1343

Abstract

A new high-strength, thermally stable, and degradable covalent organic framework (COF) -modified polylactic acid fiber (PLA) material (COF-PLA) was constructed for reinforcing the PLA material, to be used to produce environmentally friendly sand barriers. The micrographs, structure, thermal stability, and photodegradation products of COF-PLA were investigated. The results indicated that the COF material was compatible with PLA, and that the COF-PLA material took on the merits of the COF, so that it had a more regular arrangement, smoother surface, and smaller size, and was more thermostable than PLA alone. The successful incorporation of the COF improved the thermal stability of PLA. The initial pyrolysis temperature of the COF-PLA material is 313.7 °C, higher than that of the PLA material at 297.5 °C. The photodegradation products of COF-PLA and PLA indicated that the COF and PLA materials were mixed in a complex manner. After photodegradation, the COF-PLA material can produce melamine molecules that can neutralize the lactic acid and CO₂ produced by PLA, which can maintain the acid–base balance in sandy soil and is beneficial to plant growth. Therefore, COF-PLA degradation does not cause pollution, making it a promising sand-control material. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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12 pages, 611 KiB

Open AccessArticle

Mass Spectrometry Insight for Assessing the Destiny of Plastics in Seawater

by Olga V. Kuznetsova, Sergey N. Shtykov and Andrei R. Timerbaev

Polymers 2023, 15(6), 1523; https://doi.org/10.3390/polym15061523 - 19 Mar 2023

Cited by 1 | Viewed by 1383

Abstract

Plastic pollution has become an increasingly serious environmental issue that requires using reliable analytical tools to unravel the transformations of primary plastics exposed to the marine environment. Here, we evaluated the performance of the isotope ratio mass spectrometry (IRMS) technique for identifying the origin of polymer material contaminating seawater and monitoring the compositional alterations due to its chemical degradation. Of twenty-six plastic specimens available as consumer products or collected from the Mediterranean Sea, five plastics were shown to originate from biobased polymeric materials. Natural abundance carbon and hydrogen isotope measurements revealed that biopolymers incline to substantial chemical transformation upon a prolonged exposure to seawater and sunlight irradiation. To assess the seawater-mediated aging that leads to the release of micro/nano fragments from plastic products, we propose to use microfiltration. Using this non-destructive separation technique as a front end to IRMS, the fragmentation of plastics (at the level of up to 0.5% of the total mass for plant-derived polymers) was recorded after a 3-month exposure and the rate and extent of disintegration were found to be substantially different for the different classes of polymers. Another potential impact of plastics on the environment is that toxic metals are adsorbed on their surface from the seashore water. We addressed this issue by using inductively coupled mass spectrometry after nitric acid leaching and found that several metals occur in the range of 0.1–90 µg per g on naturally aged plastics and accumulate at even higher levels (up to 10 mg g⁻¹) on pristine plastics laboratory-aged in contaminated seawater. This study measured the degradation degree of different polymer types in seawater, filling in the gaps in our knowledge about plastic pollution and providing a useful methodology and important reference data for future research. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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14 pages, 1733 KiB

Open AccessArticle

A Practical Tool for the Assessment of Polymer Biodegradability in Marine Environments Guides the Development of Truly Biodegradable Plastics

by Ricardo Beiras and Sara López-Ibáñez

Polymers 2023, 15(4), 974; https://doi.org/10.3390/polym15040974 - 16 Feb 2023

Cited by 5 | Viewed by 2200

Abstract

Environmental persistence is one of the few shortcomings of plastic materials. As a consequence, alternative plastics labeled as compostable are replacing polyolefins in some commercial applications, such as food bags and trash bags. A rapid, high-throughput, and environmentally relevant method to assess the potential biodegradability in marine conditions is used to assess these materials already on the market, as well as novel bio-based polymers still in development. By fitting experimental data to a non-linear logistic model, ultimate biodegradability can be calculated without regard for incubation time. Whereas the commercial products show negligible or very low marine biodegradability, one of the novel materials exceeds the 20% biodegradation threshold relative to fully marine biodegradable PHB after 28 days. In addition, the sensitivity of the method can be enhanced and its duration reduced, at the expense of labor-demanding preconditioning of the microbial inoculum, by increasing the bacterial density in the incubation vessels. In contrast, pre-exposure of the inoculum to plastic, either in laboratory or field conditions, does not enhance the performance of the test. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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15 pages, 4516 KiB

Open AccessArticle

New Method Based on the Direct Analysis in Real Time Coupled with Time-of-Flight Mass Spectrometry to Investigate the Thermal Depolymerization of Poly(methyl methacrylate)

by Rana Salem Al Khulaifi, Mohammed Mousa AlShehri, Ahmad Abdulaziz Al-Owais, Tahani Saad Algarni, Waseem Sharaf Saeed, Ahmed Yacine Badjah-Hadj-Ahmed and Taieb Aouak

Polymers 2023, 15(3), 599; https://doi.org/10.3390/polym15030599 - 24 Jan 2023

Cited by 1 | Viewed by 2458

Abstract

In this work, the isothermal decomposition of poly(methyl methacrylate) synthesized in bulk by the radical route of methyl methacrylate in the presence of azobisisobutyronitrile as the initiator was carried out and monitored for the first time with the DART-Tof-MS technique at different temperatures. Nuclear magnetic resonance (NMR) analysis revealed a predominantly atactic microstructure, and size-exclusion chromatography (SEC) analysis indicated a number average molecular weight of 3 × 10⁵ g·mol⁻¹ and a polydispersity index of 2.47 for this polymer. Non-isothermal decomposition of this polymer carried out with thermogravimetry analysis (TGA) showed that the weight loss process occurs in two steps. The first one starts at approximately 224 °C and the second at 320 °C. The isothermal decomposition of this polymer carried out and monitored with the DART-Tof-MS method revealed only one stage of weight loss in this process, which begins at approximately 250 °C, not far from that of the second step observed in the case of the non-isothermal process conducted with the TGA method. The results obtained with the MS part of this technique revealed that the isothermal decomposition of this polymer regenerates a significant part of methyl methacrylate monomer, which increases with temperature. This process involves radical chain reactions leading to homolytic chain scissions and leading to the formation of secondary and tertiary alkyl radicals, mainly regenerating methyl methacrylate monomer through an unzipping rearrangement. Although they are in the minority, other fragments, such as the isomers of 2-methyl carboxyl, 4-methyl, penta-2,4-diene and dimethyl carbate, are also among the products detected. At 200 °C, no trace of monomer was observed, which coincides with the first step of the weight loss observed in the TGA. These compounds are different to those reported by other researchers using TGA coupled with mass spectrometry in which methyl isobutyrate, traces of methyl pyruvate and 2,3-butanonedione were detected. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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14 pages, 2011 KiB

Open AccessArticle

Magnetic Extraction of Weathered Tire Wear Particles and Polyethylene Microplastics

by Vaibhav Budhiraja, Branka Mušič and Andrej Krzan

Polymers 2022, 14(23), 5189; https://doi.org/10.3390/polym14235189 - 29 Nov 2022

Cited by 8 | Viewed by 2476

Abstract

Magnetic extraction offers a rapid and low-cost solution to microplastic (MP) separation, in which we magnetize the hydrophobic surface of MPs to separate them from complex environmental matrices using magnets. We synthesized a hydrophobic Fe-silane based nanocomposite (Fe@SiO₂/MDOS) to separate MPs from freshwater. Pristine and weathered, polyethylene (PE) and tire wear particles (TWP) of different sizes were used in the study. The weathering of MPs was performed in an accelerated weathering chamber according to ISO 4892-2:2013 standards that mimic natural weathering conditions. The chemical properties and morphology of the Fe@SiO₂/MDOS, PE and TWP were confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy, respectively. The thermal properties of PE and TWP were evaluated by Thermogravimetric analysis. Using 1.00 mg of Fe@SiO₂/MDOS nanocomposite, 2.00 mg of pristine and weathered PE were extracted from freshwater; whereas, using the same amount of the nanocomposite, 7.92 mg of pristine TWP and 6.87 mg of weathered TWP were extracted. The retrieval of weathered TWP was 13% less than that of pristine TWP, which can be attributed to the increasing hydrophilicity of weathered TWP. The results reveal that the effectiveness of the magnetic separation technique varies among different polymer types and their sizes; the weathering of MPs also influences the magnetic separation efficiency. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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15 pages, 2274 KiB

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Synergistic Adsorption of Organic Pollutants on Weathered Polyethylene Microplastics

by Vaibhav Budhiraja, Anja Urh, Petra Horvat and Andrej Krzan

Polymers 2022, 14(13), 2674; https://doi.org/10.3390/polym14132674 - 30 Jun 2022

Cited by 18 | Viewed by 2732

Abstract

Microplastics (MPs) are persistent tiny pieces of plastic material in the environment that are capable of adsorbing environmental organic pollutants from their surroundings. The interaction of MPs with organic pollutants alters their environmental behavior, i.e., their adsorption, degradation and toxicity, etc. Polyethylene (PE) is the most widely used plastic material. The environmental weathering of PE results in changes to its surface chemistry, making the polymer a much better vector for organic pollutants than virgin PE. In this study, a laboratory-accelerated weathering experiment was carried out with a virgin PE film and an oxidatively degradable PE (OXO-PE) film, i.e., PE modified by the addition of a pro-oxidant catalyst. The degradation of PE and OXO-PE was assessed through Fourier transform infra-red (FTIR) spectroscopy and their wettability was measured by contact angle (CA) measurements. Their thermal properties and morphology were studied using thermogravimetric analyses (TGA) and scanning electron microscopy (SEM), respectively. Further, the adsorption of two model organic pollutants onto weathered and virgin PE was analyzed. Triclosan (TCS) and methylparaben (MeP) were chosen as model organic pollutants for the adsorption experiment due to their frequent use in the cosmetics industry, their uncontrolled release into the environment and their toxicity. The adsorption of both model pollutants onto PE and OXO-PE MP was analyzed by using gas chromatography with a flame ionization detector (GC-FID). The adsorption of MeP onto OXO-PE was higher than onto PE MPs. However, TCS showed insignificant adsorption onto PE and OXO-PE. When both pollutants were present simultaneously, the adsorption of TCS onto both PE and OXO-PE was significantly influenced by the presence of MeP. This result demonstrates that the adsorption behavior of one pollutant can be significantly altered by the presence of another pollutant. Both the effect of weathering on the adsorption of organic pollutants as well as the interaction between organic pollutants adsorbing onto MPs is highly relevant to actual MP pollution in the environment, where MPs are exposed to weathering conditions and mixtures of organic pollutants. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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14 pages, 1417 KiB

Open AccessArticle

Degradation of P(3HB-co-4HB) Films in Simulated Body Fluids

by Juraj Vodicka, Monika Wikarska, Monika Trudicova, Zuzana Juglova, Aneta Pospisilova, Michal Kalina, Eva Slaninova, Stanislav Obruca and Petr Sedlacek

Polymers 2022, 14(10), 1990; https://doi.org/10.3390/polym14101990 - 13 May 2022

Cited by 4 | Viewed by 2242

Abstract

A novel model of biodegradable PHA copolymer films preparation was applied to evaluate the biodegradability of various PHA copolymers and to discuss its biomedical applicability. In this study, we illustrate the potential biomaterial degradation rate affectability by manipulation of monomer composition via controlling the biosynthetic strategies. Within the experimental investigation, we have prepared two different copolymers of 3-hydroxybutyrate and 4-hydroxybutyrate—P(3HB-co-36 mol.% 4HB) and P(3HB-co-66 mol.% 4HB), by cultivating the thermophilic bacterial strain Aneurinibacillus sp. H1 and further investigated its degradability in simulated body fluids (SBFs). Both copolymers revealed faster weight reduction in synthetic gastric juice (SGJ) and artificial colonic fluid (ACF) than simple homopolymer P3HB. In addition, degradation mechanisms differed across tested polymers, according to SEM micrographs. While incubated in SGJ, samples were fragmented due to fast hydrolysis sourcing from substantially low pH, which suggest abiotic degradation as the major degradation mechanism. On the contrary, ACF incubation indicated obvious enzymatic hydrolysis. Further, no cytotoxicity of the waste fluids was observed on CaCO-2 cell line. Based on these results in combination with high production flexibility, we suggest P(3HB-co-4HB) copolymers produced by Aneurinibacillus sp. H1 as being very auspicious polymers for intestinal in vivo treatments. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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12 pages, 2281 KiB

Open AccessArticle

Polyisocyanide Quaternary Ammonium Salts with Exceptionally Star-Shaped Structure for Enhanced Antibacterial Properties

by Hongguang Zhang, Lijia Liu, Peng Hou, Hong Pan and Shuang Fu

Polymers 2022, 14(9), 1737; https://doi.org/10.3390/polym14091737 - 24 Apr 2022

Cited by 7 | Viewed by 1872

Abstract

The development of non-polluting and non-hazardous polymeric antimicrobial agents has become a hot issue in current research and development. Among them, polymer quaternary ammonium salts are thought to be one of the most promising materials for antibacterial efficacy. Here, we present an efficient strategy for synthesizing polyisocyanide quaternary ammonium salts (PQASs) with a novel star-shaped structure. Benefitting from the novel structure, increased cation density and enhanced water solubility, the prepared star polyisocyanide quaternary ammonium salts (S-PQASs) exhibit excellent antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In particular, S-POcQAS-M₅₀ (where M stands for isonitrile monomer and 50 stands for the initial feeding ratio) showed the best antimicrobial activity with minimum inhibitory concentration (MIC) of 17 and 20 µg/mL against E. coli and S. aureus, respectively. It was also found that the unique star-shaped structure can give QASs with improved antimicrobial performance compared with our previously prepared linear quaternary ammonium salts (L-PQASs). These results demonstrated that the antibacterial activity of QASs is closely related to its structure. This work provides an idea for the design of efficient polymeric antimicrobial agents. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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Review

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14 pages, 1399 KiB

Open AccessReview

A Review on the Role of Earthworms in Plastics Degradation: Issues and Challenges

by Shahad Khaldoon, Japareng Lalung, Umrana Maheer, Mohamad Anuar Kamaruddin, Mohd Firdaus Yhaya, Eman S. Alsolami, Hajer S. Alorfi, Mahmoud A. Hussein and Mohd Rafatullah

Polymers 2022, 14(21), 4770; https://doi.org/10.3390/polym14214770 - 07 Nov 2022

Cited by 7 | Viewed by 3251

Abstract

Recently, the contribution of earthworms to plastic degradation and their capability to swallow smaller plastic fragments, known as microplastics, has been emphasized. The worm physically changes the size of microplastics and enhances microbial activities to increase the possibility of degradation. However, no research has shown that earthworms can chemically degrade microplastics to an element form, CO₂ or H₂O. In this review, previous research has been thoroughly explored to analyse the role that earthworms could play in plastic degradation in the soil. Earthworms can significantly affect the physical characteristics of plastics. However, earthworms’ abilities to chemically degrade or change the chemical structure of plastics and microplastics have not been observed. Additionally, earthworms exhibit selective feeding behaviour, avoiding areas containing a high plastics concentration and rejecting plastics. Consequently, earthworms’ abilities to adapt to the microplastics in soil in the environment can cause a problem. Based on this review, the challenges faced in earthworm application for plastic degradation are mostly expected to be associated with the toxicity and complexity of the plastic material and environmental factors, such as the moisture content of the soil and its temperature, microbial population, and feeding method. Full article

(This article belongs to the Special Issue Degradation and Stabilization of Polymer Materials)

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