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Gels
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Advances in Biopolymer Aerogels and Their Composites
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Advances in Biopolymer Aerogels and Their Composites

A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Chemistry and Physics".

Deadline for manuscript submissions: closed (30 May 2023) | Viewed by 6545

Special Issue Editors

Prof. Dr. Jian Liu

E-Mail Website1 Website2
Guest Editor
College of Energy, Xiamen University, Xiamen 361005, China
Interests: bio-based materials; lignocellulosic biomass utilization; cellulose hydrolysis; functional food; reaction kinetics
Prof. Dr. Huazheng Sai

E-Mail Website
Guest Editor
School of Chemistry and Chemical Engineering, Inner Mongolia University of Science and Technology, Baotou 014010, China
Interests: aerogels; composites; thermal insulation; biopolymer

Special Issue Information

Dear Colleagues,

Aerogels with ultra-high porosity have enormous potential to be used in various fields, such as thermal insulation, acoustic insulation, sensor, adsorption, catalysis, energy storage, electromagnetic shielding, drug delivery, etc. Aerogels with different compositions and microstructures are constantly being developed to solve the inherent defects of aerogels (e.g., high brittleness) and endow them with novel properties to expand their application fields. As sustainable raw material, biopolymer is becoming an ideal precursor for the preparation of aerogel due to its rich sources and surface groups. Although there have been many scientific works on biopolymer aerogels and their composites in recent years, compared with inorganic oxide aerogels represented by silica aerogels, their industrialization and practical application still face many challenges. Therefore, it is necessary to continuously explore different biopolymer sources and synthesis routes to prepare novel aerogels.

This Special Issue focuses on recent research and advances in biopolymer aerogels and their composites, such as native biopolymer aerogels, biopolymer-derived carbon aerogels, biopolymer–inorganic hybrid aerogels, and biopolymer–polymer and biopolymer–biopolymer composites. In addition, the issue focuses not only on the development of the composition or synthesis routes of biopolymer-based aerogels, but also different applications, pore structure analysis, and simulation.

Prof. Dr. Jian Liu
Prof. Dr. Huazheng Sai
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. Gels is an international peer-reviewed open access monthly 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 2600 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

  • biopolymer aerogels
  • composite aerogels
  • biopolymer-derived aerogels
  • mechanical properties
  • green synthesis
  • functionalization

Published Papers (4 papers)

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Research

34 pages, 10679 KiB  
Article
A Comparative Thermoacoustic Insulation Study of Silica Aerogels Reinforced with Reclaimed Textile Fibres: Cotton, Polyester and Wool
by Teresa Linhares, Vitor H. Carneiro, Maria T. Pessoa de Amorim and Luisa Durães
Gels 2023, 9(7), 548; https://doi.org/10.3390/gels9070548 - 05 Jul 2023
Cited by 2 | Viewed by 1277
Abstract
Silica aerogels are highly porous materials with exceptional thermal insulation performance. They become even more attractive if combined thermal and acoustic insulation is achieved. Silica aerogel composites reinforced with fibres are an ingenious way to surpass the fragility stemmed from the aerogel’s intrinsic [...] Read more.
Silica aerogels are highly porous materials with exceptional thermal insulation performance. They become even more attractive if combined thermal and acoustic insulation is achieved. Silica aerogel composites reinforced with fibres are an ingenious way to surpass the fragility stemmed from the aerogel’s intrinsic porosity, and textile fibres are good sound absorption materials. Reclaimed fibres are a relatively low-cost feedstock and were obtained in this work exclusively through mechanical processes from textile wastes, thus promoting the concept of circular economy, namely for cotton, polyester and wool fibres. These reclaimed fibres were used as reinforcement matrices for silica aerogel composites obtained from sol–gel transformation of tetraethyl orthosilicate and isobutyltriethoxysilane/or vinyltrimethoxysilane precursors and dried at ambient pressure after silylation. Silica aerogel composites reinforced with reclaimed cotton fibres had the best sound absorption coefficient (a peak value of 0.89), while the polyester-reinforced composite exhibited the lowest thermal conductivity (k = ~24 mW m−1 K−1, Hot Disk). The better combined results on thermal and acoustic insulation were achieved by the wool-reinforced composites. The thermal conductivity values were less than 27 mW m−1 K−1, and the sound absorption coefficient achieved a peak value of 0.85. Therefore, the aerogel composites developed here can be selected for thermal or/and acoustic barriers by choosing a suitable type of fibre. Their design and preparation protocol followed environmental-friendly and cost-effective approaches. Full article
(This article belongs to the Special Issue Advances in Biopolymer Aerogels and Their Composites)
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13 pages, 3028 KiB  
Article
Robust, Fire-Retardant, and Water-Resistant Wood/Polyimide Composite Aerogels with a Hierarchical Pore Structure for Thermal Insulation
by Lu Zhao, Junyong Chen, Defang Pan and Yan Hou
Gels 2023, 9(6), 467; https://doi.org/10.3390/gels9060467 - 06 Jun 2023
Cited by 4 | Viewed by 1329
Abstract
The use of energy-saving materials is an effective strategy for decreasing energy consumption and carbon emission. Wood is a type of biomass material with a natural hierarchical structure, which results in its high thermal insulation. It has been widely used in construction. However, [...] Read more.
The use of energy-saving materials is an effective strategy for decreasing energy consumption and carbon emission. Wood is a type of biomass material with a natural hierarchical structure, which results in its high thermal insulation. It has been widely used in construction. However, developing wood-based materials without flammability and dimensional instability is still a challenge. Herein, we developed a wood/polyimide composite aerogel with a well-preserved hierarchical pore structure and dense hydrogen bonds inside, resulting in its excellent chemical compatibility and strong interfacial interactions between its two components. This novel wood-based composite was fabricated by removing most hemicellulose and lignin from natural wood, followed by the fast impregnation using an ‘in situ gel’ process. The introduction of polyimide into delignified wood substantially improved its mechanical properties, with the compression resistance being improved by over five times. Notably, the thermal conductivity coefficient of the developed composite was approximately half that of natural wood. Furthermore, the composite exhibited excellent fire-retardancy, hydrophobicity, thermal insulation, and mechanical properties. This study provides a novel method for wood modification, which not only aids interfacial compatibility between wood and polyimide but also retains the properties of the two components. The developed composite can effectively reduce energy consumption, making it promising for practical and complex thermal insulation applications. Full article
(This article belongs to the Special Issue Advances in Biopolymer Aerogels and Their Composites)
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13 pages, 3422 KiB  
Article
Graphene Oxide/Styrene-Butadiene Latex Hybrid Aerogel with Improved Mechanical Properties by PEI Grafted GO and CNT
by Zetian Zhao, Lina Zhang, Yinghu Song, Lichun Ma, Jialiang Li, Min Zhao, Xueliang Ji, Jianfei Gao, Guojun Song and Xiaoru Li
Gels 2023, 9(5), 419; https://doi.org/10.3390/gels9050419 - 16 May 2023
Cited by 2 | Viewed by 1477
Abstract
Graphene oxide aerogel (GOA) has wide application prospects due to its low density and high porosity. However, the poor mechanical properties and unstable structure of GOA have limited its practical applications. In this study, polyethyleneimide (PEI) was used to graft onto the surface [...] Read more.
Graphene oxide aerogel (GOA) has wide application prospects due to its low density and high porosity. However, the poor mechanical properties and unstable structure of GOA have limited its practical applications. In this study, polyethyleneimide (PEI) was used to graft onto the surface of GO and carbon nanotubes (CNTs) to improve compatibility with polymers. Composite GOA was prepared by adding styrene-butadiene latex (SBL) to the modified GO and CNTs. The synergistic effect of PEI and SBL, resulted in an aerogel with excellent mechanical properties, compressive resistance, and structural stability. When the ratio of SBL to GO and GO to CNTs was 2:1 and 7:3, respectively, the obtained aerogel performance was the best, and the maximum compressive stress was 784.35% higher than that of GOA. The graft of PEI on the surface of GO and CNT could improve the mechanical properties of the aerogel, with greater improvements observed with grafting onto the surface of GO. Compared with GO/CNT/SBL aerogel without PEI grafting, the maximum stress of GO/CNT–PEI/SBL aerogel increased by 5.57%, that of GO–PEI/CNT/SBL aerogel increased by 20.25%, and that of GO–PEI/CNT–PEI/SBL aerogel increased by 28.99%. This work not only provided a possibility for the practical application of aerogel, but also steered the research of GOA in a new direction. Full article
(This article belongs to the Special Issue Advances in Biopolymer Aerogels and Their Composites)
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13 pages, 6164 KiB  
Article
Directional-Freezing-Assisted In Situ Sol–Gel Strategy to Synthesize High-Strength, Fire-Resistant, and Hydrophobic Wood-Based Composite Aerogels for Thermal Insulation
by Yan Hou, Junyong Chen, Defang Pan and Lu Zhao
Gels 2023, 9(2), 170; https://doi.org/10.3390/gels9020170 - 20 Feb 2023
Cited by 2 | Viewed by 1928
Abstract
The undesirable inherent natural characteristics of wood, such as low mechanical strength, flammability, and hygroscopicity, limit its potential applications in the thermal insulation industry. Overcoming these disadvantages can greatly expand the application scope of wood. A new attempt at wood modification, the directional-freezing-assisted [...] Read more.
The undesirable inherent natural characteristics of wood, such as low mechanical strength, flammability, and hygroscopicity, limit its potential applications in the thermal insulation industry. Overcoming these disadvantages can greatly expand the application scope of wood. A new attempt at wood modification, the directional-freezing-assisted in situ sol–gel strategy, was used to obtain wood–silica composite aerogels with the unique multi-level ordered porous structure of wood. This method enables silica nanoparticles to successfully replace lignin and facilitates the formation of strong hydrogen bonds between the silica and cellulose molecules. This results in improved mechanical properties for the composite with a density similar to that of natural wood but a mechanical strength that can be up to five times greater. The thermal conductivity coefficient is also reduced to 0.032 W (m·K)−1 compared to 0.066 W (m·K)−1 for natural wood. This aerogel composite exhibits improved fire resistance and hygroscopicity, with a decomposition temperature increase of approximately 45 °C compared to natural wood. Additionally, the composite demonstrates self-extinguishing behavior, with the structure remaining intact after combustion, and thus enhanced fire resistance. Simultaneously, the enhanced aerogel composite hydrophobicity, with water contact angle of up to 120°, is beneficial to a prominent thermal insulation performance in a high-humidity environment. The successful synthesis of wood-based composite aerogels provides a new and innovative approach for the utilization of wood resources in the thermal insulation industry. Full article
(This article belongs to the Special Issue Advances in Biopolymer Aerogels and Their Composites)
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