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Polymers
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Polymeric Self-Healing Materials II
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Polymeric Self-Healing Materials II

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Smart and Functional Polymers".

Deadline for manuscript submissions: closed (15 April 2024) | Viewed by 8881

Special Issue Editors

Dr. Marialuigia Raimondo

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Guest Editor
Department of Industrial Engineering, University of Salerno, 84084 Fisciano, SA, Italy
Interests: physico-chemical properties, structure, morphology and durability of macromolecular systems; design and development of smart and/or nanostructured materials; synthesis of self-healing microcapsules; multifunctional carbon-based hybrid materials for aircraft lightning strike protection; thermosetting composites with self-restoration function capable at very low temperatures; conductive and flame retardant nanofilled aeronautic composites; FTIR spectroscopy; morphological analysis by Atomic Force Microscopy (AFM) and Tunneling Atomic Force Microscopy (TUNA) techniques
Special Issues, Collections and Topics in MDPI journals
Dr. Andrea Sorrentino

E-Mail Website
Guest Editor
Institute of Polymers, Composites and Biomaterials (IPCB), National Research Council of Italy (CNR), Via Previati 1/C, 23900 Lecco, Italy
Interests: process–properties relashionships; morphology and properties of polymeric materials; polymer processing; injection and compression moulding; nanofunctionalized polymer materials for barrier and electrical applications; polymer (bio/photo)-degradation; bionanocomposites materials; thermomechanical properties; biodegradable materials; high performances composite materials; materials for sensing; materials for drug delivery; self-healing materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A self-healing material has the ability to restore lost or degraded performance using resources that are inherently available in the material itself. Ideally, this process should be fast and should be able to occur for an infinite number of cycles without any external stimuli. Unfortunately, persistent irreversible mechanisms, low chemical stability, and weak mechanical performance mean that the present systems are far from achieving these capabilities.

Polymers are one of the most broadly used materials in daily life. They have several advantages, such as inexpensive cost, good processability, and low density. The incorporation of self-healing mechanisms in polymeric materials promises to further expand their use by extending the lifetime of structural and functional polymer-based systems. This Special Issue aims to represent the state of the art in this field and provide systematic information on self-healing mechanisms, characterization techniques, and structure–property relationships. We hope to provide the community with new ideas and perspectives, as we are firmly convinced that these bioinspired materials can be applied in most modern engineering applications.

Dr. Marialuigia Raimondo
Dr. Andrea Sorrentino
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

  • self-healing materials
  • bioinspired materials
  • healing mechanisms
  • supramolecular self-healing
  • capsule-based self-healing materials
  • intrinsic self-healing materials
  • vascular self-healing materials
  • characterization techniques of healing performance
  • self-healable fiber-reinforced resins for aerospace applications
  • self-healing conductive epoxy systems

Published Papers (5 papers)

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Research

20 pages, 6135 KiB  
Article
Influence of Catalyst Content and Epoxy/Carboxylate Ratio on Isothermal Creep of Epoxy Vitrimers
by Barbara Palmieri, Fabrizia Cilento, Eugenio Amendola, Teodoro Valente, Stefania Dello Iacono, Michele Giordano and Alfonso Martone
Polymers 2023, 15(18), 3845; https://doi.org/10.3390/polym15183845 - 21 Sep 2023
Viewed by 1123
Abstract
In the present work, a commercial epoxy based on epoxy anhydride and tertiary amine was modified by a metallic catalyst (Zn2+) to induce vitrimeric behavior by promoting the transesterification reaction. The effect of two different epoxy/acid ratios (1 and 0.6) at [...] Read more.
In the present work, a commercial epoxy based on epoxy anhydride and tertiary amine was modified by a metallic catalyst (Zn2+) to induce vitrimeric behavior by promoting the transesterification reaction. The effect of two different epoxy/acid ratios (1 and 0.6) at two different zinc acetate amounts (Zn(Ac)2) on the thermomechanical and viscoelastic performances of the epoxy vitrimers were investigated. Creep experiments showed an increase in molecular mobility above the critical “Vitrimeric” temperature (Tv) of 170 °C proportionally to the amount of Zn(Ac)2. A procedure based on Burger’s model was set up to investigate the effect of catalyst content on the vitrimer ability to flow as the effect of the dynamic exchange reaction. The analysis showed that in the case of a balanced epoxy/acid formulation, the amount of catalyst needed for promoting molecular mobility is 5%. This system showed a value of elastic modulus and dynamic viscosity at 170 °C of 9.50 MPa and 2.23 GPas, respectively. The material was easily thermoformed in compression molding, paving the way for the recyclability and weldability of the thermoset system. Full article
(This article belongs to the Special Issue Polymeric Self-Healing Materials II)
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18 pages, 11401 KiB  
Article
Multifunctional Properties of Polyhedral Oligomeric Silsesquioxanes (POSS)-Based Epoxy Nanocomposites
by Liberata Guadagno, Andrea Sorrentino, Raffaele Longo and Marialuigia Raimondo
Polymers 2023, 15(10), 2297; https://doi.org/10.3390/polym15102297 - 13 May 2023
Cited by 4 | Viewed by 1558
Abstract
In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to [...] Read more.
In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to formulate multifunctional structural nanocomposites tailored for aeronautic and aerospace applications. This work aims to demonstrate how the skillful combination of desired properties, such as good electrical, flame-retardant, mechanical, and thermal properties, is obtainable thanks to the advantages connected with nanoscale incorporations of nanosized CNTs with POSS. The special hydrogen bonding-based intermolecular interactions between the nanofillers have proved to be strategic in imparting multifunctionality to the nanohybrids. All multifunctional formulations are characterized by a Tg centered at values close to 260 °C, fully satisfying structural requirements. Infrared spectroscopy and thermal analysis confirm the presence of a cross-linked structure characterized by a high curing degree of up to 94% and high thermal stability. Tunneling atomic force microscopy (TUNA) allows to detect the map of the electrical pathways at the nanoscale of the multifunctional samples, highlighting a good dispersion of the carbon nanotubes within the epoxy resin. The combined action of POSS with CNTs has allowed to obtain the highest values of self-healing efficiency if compared to those measured for samples containing only POSS in the absence of CNTs. Full article
(This article belongs to the Special Issue Polymeric Self-Healing Materials II)
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26 pages, 6056 KiB  
Article
Self-Healing Poly(urea formaldehyde) Microcapsules: Synthesis and Characterization
by Jehan Kothari and Jude O. Iroh
Polymers 2023, 15(7), 1668; https://doi.org/10.3390/polym15071668 - 27 Mar 2023
Cited by 3 | Viewed by 2055
Abstract
Smart coatings and smart polymers have been garnering great interest in recent times due to their novel characteristics, such as being self-restoring, self-cleaning, and self-healing. However, most self-healing materials have a low glass transition temperature (Tg) and are inadequate for the [...] Read more.
Smart coatings and smart polymers have been garnering great interest in recent times due to their novel characteristics, such as being self-restoring, self-cleaning, and self-healing. However, most self-healing materials have a low glass transition temperature (Tg) and are inadequate for the repair of advanced composites. Because of their low Tg, the conventional self-healing materials plasticize and weaken the composites. In this study, moderate to high temperature self-healing microcapsules, capable of healing and thus stopping crack propagation, are prepared. The microcapsules were prepared using a two-step process involving the synthesis of poly(urea formaldehyde) (PUF) prepolymer, followed by the encapsulation of hexamethylene diisocyanate (HDI) in an oil-in-water emulsion to form a crosslinked PUF shell. Diisocyanates are of particular interest as self-healing encapsulants because of their diversity of structure and fast rate of hydrolysis. Successful encapsulation was verified by Fourier transform infrared spectroscopy (FTIR) and optical microscopy. Thermogravimetric analysis (TGA) was used to characterize the thermal properties of microcapsules. The onset temperature for microcapsule degradation varied from 155 °C to 195 °C. Dynamic mechanical analysis (DMA) was used to determine the thermomechanical response of microcapsule/epoxy films. DMA showed that the glass transition temperature (Tg) of the epoxy/microcapsule composite was greater than the Tg for neat epoxy and varied between 34 and 65 °C. The TGA analysis of the epoxy/microcapsule composite shows that the thermal stability and char retention of the epoxy/microcapsule composite increased and the low temperature decomposition peak at 150 °C, associated with the microcapsule, disappeared after the DMA test, indicating the occurrence of a reaction between HDI and the epoxy to form a crosslinked polyurea network structure. Full article
(This article belongs to the Special Issue Polymeric Self-Healing Materials II)
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22 pages, 11115 KiB  
Article
Optimised Sunflower Oil Content for Encapsulation by Vibrating Technology as a Rejuvenating Solution for Asphalt Self-Healing
by Jose L. Concha, Rodrigo Delgadillo, Luis E. Arteaga-Pérez, Cristina Segura and Jose Norambuena-Contreras
Polymers 2023, 15(6), 1578; https://doi.org/10.3390/polym15061578 - 22 Mar 2023
Cited by 6 | Viewed by 1592
Abstract
This study aimed to determine an optimal dosage of sunflower oil (i.e., Virgin Cooking Oil, VCO) as a rejuvenator for asphalt self-healing purposes, evaluating its effect on the chemical (carbonyl, and sulfoxide functional groups), physical (penetration, softening point, and viscosity), and rheological (dynamic [...] Read more.
This study aimed to determine an optimal dosage of sunflower oil (i.e., Virgin Cooking Oil, VCO) as a rejuvenator for asphalt self-healing purposes, evaluating its effect on the chemical (carbonyl, and sulfoxide functional groups), physical (penetration, softening point, and viscosity), and rheological (dynamic shear modulus, and phase angle) properties of long-term aged (LTA) bitumen. Five concentrations of sunflower oil (VCO) were used: 1%, 2%, 3%, 4%, and 5% vol. of LTA bitumen. VCO was encapsulated in alginate biopolymer under vibrating jet technology using three biopolymer:oil (B:O) mass ratios: 1:1, 1:5, and 1:9. The physical, thermal, and mechanical properties of the capsules were studied, as well as their effect on the physical properties of dense asphalt mixtures. The main results showed that an optimal VCO content of 4% vol. restored the chemical, physical, and rheological properties of LTA bitumen to a short-term ageing (STA) level. VCO capsules with B:O ratios of 1:5 presented good thermal and mechanical stability, with high encapsulation efficiency. Depending on the B:O ratio, the VCO capsule dosage to rejuvenate LTA bitumen and asphalt mixtures varied between 5.03–15.3% wt. and 0.24–0.74% wt., respectively. Finally, the capsule morphology significantly influenced the bulk density of the asphalt mixtures. Full article
(This article belongs to the Special Issue Polymeric Self-Healing Materials II)
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15 pages, 2271 KiB  
Article
Rheological and Self-Healing Behavior of Hydrogels Synthesized from l-Lysine-Functionalized Alginate Dialdehyde
by Arlina Prima Putri, Ranjita K. Bose, Mochamad Chalid and Francesco Picchioni
Polymers 2023, 15(4), 1010; https://doi.org/10.3390/polym15041010 - 17 Feb 2023
Cited by 3 | Viewed by 1777
Abstract
Alginate dialdehyde and l-lysine-functionalized alginate dialdehyde were prepared to provide active aldehyde and l-lysine sites along the alginate backbone, respectively. Different concentrations of substrates and the reduction agent were added, and their influence on the degree of l-lysine substitution was [...] Read more.
Alginate dialdehyde and l-lysine-functionalized alginate dialdehyde were prepared to provide active aldehyde and l-lysine sites along the alginate backbone, respectively. Different concentrations of substrates and the reduction agent were added, and their influence on the degree of l-lysine substitution was evaluated. An amination reduction reaction (with l-lysine) was conducted on alginate dialdehyde with a 31% degree of oxidation. The NMR confirmed the presence of l-lysine functionality with the degree of substitution of 20%. The structural change of the polymer was observed via FTIR spectroscopy, confirming the formation of Schiff base covalent linkage after the crosslinking. The additional l-lysine sites on functionalized alginate dialdehyde provide more crosslinking sites on the hydrogel, which leads to a higher modulus storage rate than in the original alginate dialdehyde. This results in dynamic covalent bonds, which are attributed to the alginate derivative–gelatin hydrogels with shear-thinning and self-healing properties. The results suggested that the concentration and stoichiometric ratio of alginate dialdehyde, l-lysine-functionalized alginate dialdehyde, and gelatin play a fundamental role in the hydrogel’s mechanical properties. Full article
(This article belongs to the Special Issue Polymeric Self-Healing Materials II)
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