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Lignin Based Materials: Structure, Properties and Applications

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

Deadline for manuscript submissions: closed (25 May 2023) | Viewed by 46940

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Dr. Oihana Gordobil

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Guest Editor

“Materials + Technologies” Research Group (GMT), Chemical and Environmental Engineering Department, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 San Sebastian, Spain
Interests: lignin chemistry and valorization; lignin conversion processes; chemical modification of lignin; bio-based products and materials; natural additives; lignocellulosic biomass and biorefinery; wood technology; spectroscopy and chemometrics
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Dr. Stefan Beisl

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Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Getreidemarkt 9/166, Vienna 1060, Austria
Interests: lignocellulosic biomass pretreatment and biorefinery; precipitation processes; colloidal lignin production and application; lignin fractionation processes; membrane separation processes; bio-based products and materials

Dr. René Herrera Díaz

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1. Chemical and Environmental Engineering Department, University of the Basque Country (UPV/EHU), Plaza Europa 1, 20018 San Sebastian, Spain
2. Innorenew CoE, Livade 6, 6310 Izola, Slovenia
Interests: bulk and surface wood modification; bio-based materials; green additives; biorefinery and applications; exploration of new analytical techniques (NIR-Vis spectroscopy, Hiperspectral images, chemometrics)
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear colleagues,

Lignin is a heterogeneous natural polymer with an aromatic structure that constitutes 15-35% of lignocellulosic biomass. Technical lignins are currently produced in large quantities annually as a by-product from chemical pulping operations and lignocellulosic ethanol production. However, the valorization rate for this abundant renewable resource is still less than 2%. Therefore, lignin recovery from side streams and conversion into diverse and valuable products for high-value applications is an attractive opportunity for further development of biorefineries in the near future from a circular economy perspective.

The control of key parameters during lignin extraction or recovery steps determines the quality of the resultant lignin polymer in terms of purity, molecular characteristics, properties and color. Regarding lignin conversion, many past studies have demonstrated its huge potential to produce valuable fine chemicals and biofuels through thermochemical fragmentation and biological conversion pathways. Moreover, the incorporation of lignin and lignin-derived products, both as an additive in natural and synthetic polymers and as a precursor to synthesize various target applications (including polyurethanes and phenol-formaldehyde resins), and carbon-based materials has been extensively investigated over the years. Recently, lignin’s multi-functionality and biological activity has attracted a great deal of attention within the scientific community. New and innovative applications for lignin valorization are emerging in different fields, including medicine, pharmaceuticals and cosmetics.

Today, the most important research related to lignin valorization aims to overcome technical limitations and increase performance in final applications through the development of sustainable and efficient conversion processes. At present, the evaluation of lignin performance in various applications is the real bottleneck in lignin engineering due to the polymer’s enormous variability and chemical heterogeneity. Current research approach is based on time-consuming characterization techniques and the lack of standardized procedures for analysis. Therefore, the development of fast and reliable analytical methodologies for the classification and prediction of lignin structure-properties-performance relationships could promote lignin valorization progress.

You are kindly invited to contribute interdisciplinary and original research articles and review articles focused on novel aspects and strategies related to lignin valorization, current requirements linked to regulatory aspects in specific applications, future industrial use, research directions and prospects as well as developments in qualitative and quantitative fast analytical solutions for lignin processing and quality control.

Welcomed submissions include, but not limited to, the topics listed below:

Influence of lignin impurities on its valorization and applications
Separation and purification technologies of lignin-derived compounds and applications
Functional lignin-based materials: hydrogels, nanocarriers, biosorbents, nanoparticles
Chemical modification of lignin to develop tailored lignin-derived products
Application of lignin in coatings, adhesives, resins, plasticizers and flame retardants
Antioxidant performance of lignin in real application (applied tests, not just standard methods)
Improving UV absorbance of lignin
Structure-properties-performance relationships
Regulatory and economic hurdles to bring high-value lignin applications to the market
Fast and easy analytical methods for industrial process control
Approaches to produce lignins with constant quality
Performance of sulfur-free lignins compared to pulp and paper lignins

Dr. Oihana Gordobil
Dr. Stefan Beisl
Dr. René Herrera Díaz
Guest Editors

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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.

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Keywords

Circular economy
lignin conversion
quality control
lignin performance
novel applications

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Published Papers (10 papers)

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Research

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15 pages, 3901 KiB

Open AccessArticle

Exploring Fully Biobased Adhesives: Sustainable Kraft Lignin and 5-HMF Adhesive for Particleboards

by Liam Dorn, Arthur Thirion, Masoumeh Ghorbani, Luis M. Olaechea and Ingo Mayer

Polymers 2023, 15(12), 2668; https://doi.org/10.3390/polym15122668 - 13 Jun 2023

Cited by 5 | Viewed by 2370

Abstract

Most adhesives used in the wood-based panel (WBP) industry are petroleum-based and are associated with environmental impact and price fluctuations. Furthermore, most have potential adverse health impacts, such as formaldehyde emissions. This has led to interest from the WBP industry in developing adhesives with bio-based and/or non-hazardous components. This research focuses on the replacement of phenol-formaldehyde resins by Kraft lignin for phenol substitution and 5-hydroxymethylfurfural (5-HMF) for formaldehyde substitution. Resin development and optimization was carried out regarding varying parameters such as molar ratio, temperature or pH. The adhesive properties were analyzed using a rheometer, gel timer and a differential scanning calorimeter (DSC). The bonding performances were evaluated using an Automated Bonding Evaluation System (ABES). Particleboards were produced using a hot press, and their internal bond strength (IB) was evaluated according to SN EN 319. Hardening of the adhesive could be achieved at low temperatures by increasing or decreasing the pH. The most promising results were obtained at pH 13.7. The adhesive performances were improved by adding filler and extender (up to 28.6% based on dry resin) and several boards were produced reaching P1 requirements. A particleboard achieved a mean IB of 0.29 N/mm², almost reaching almost P2 requirements. However, adhesive reactivity and strength must be improved for industrial use. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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13 pages, 4811 KiB

Open AccessArticle

Metal–Organic-Framework-Mediated Fast Self-Assembly 3D Interconnected Lignin-Based Cryogels in Deep Eutectic Solvent for Supercapacitor Applications

by Rui Lou, Qihang Cao, Taoyuan Niu, Yiyi Zhang, Yanan Zhang, Zhiwei Wang and Xiao Zhang

Polymers 2023, 15(8), 1824; https://doi.org/10.3390/polym15081824 - 8 Apr 2023

Cited by 6 | Viewed by 2524

Abstract

A cost-effective and sustainable method is successfully developed to produce lignin-based cryogels with a mechanically robust 3D interconnected structure. A choline chloride–lactic acid (ChCl–LA)-based deep eutectic solvent (DES) is used as a cosolvent to promote the synthesis of lignin–resorcinol–formaldehyde (LRF) gels that can self-assemble a robust string-bead-like framework. The molar ratio of LA to ChCl in DES has a significant influence on the gelation time and properties of the ensuing gels. Moreover, it is discovered that doping the metal–organic framework (MOF) during the sol–gel process can greatly accelerate the gelation of lignin. It takes a mere 4 h to complete the LRF gelation process at a DES ratio of 1:5 combined with 5% MOF. This study yields LRF carbon cryogels doped with copper that exhibit 3D interconnected bead-like carbon spheres with a prominent micropore of 1.2 nm. A specific capacitance as high as 185 F g⁻¹ can be obtained for the LRF carbon electrode at a current density of 0.5 A g⁻¹, and it has an excellent long-term cycling stability. This study provides a novel method of synthesizing high-lignin-content carbon cryogels with promising potential for application in the field of energy storage devices. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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17 pages, 4150 KiB

Open AccessArticle

Effect of Thermal Oxygen Aging Mode on Rheological Properties and Compatibility of Lignin-Modified Asphalt Binder by Dynamic Shear Rheometer

by Meng Cai, Xun Zhao, Xuanzhen Han, Peng Du, Yi Su and Cheng Cheng

Polymers 2022, 14(17), 3572; https://doi.org/10.3390/polym14173572 - 30 Aug 2022

Cited by 10 | Viewed by 2165

Abstract

Lignin is abundant in nature. The use of lignin in the asphalt pavement industry can improve pavement performance while effectively optimizing pavement construction costs. The purpose of this paper is to study the effect of lignin on the anti-aging properties of asphalt. Commercial lignin was selected to prepare a lignin-modified asphalt binder. The properties of lignin-modified asphalt were studied by rheological experiments. The high-temperature rheological properties of two kinds of base asphalt and modified asphalt samples with different contents of lignin under three conditions of original, rolling thin film oven (RTFO) aging, and pressure aging vessel (PAV) were tested and analyzed with temperature sweep, frequency sweep, and multiple stress creep recovery (MSCR) tests. By comparing the variation laws of evaluation indicators, such as complex shear modulus G*, phase angle δ, anti-aging index, cumulative strain, and viscous component G_v, we found that lignin could effectively improve the high-temperature stability of base asphalt, but it had a negative impact on the compatibility issues of base asphalt. Meanwhile, lignin played a filling role in the base asphalt, and the increase in viscosity was the fundamental reason for improving the high-temperature stability of the base asphalt. The research results indicated that lignin could effectively improve the anti-aging performance of asphalt and play a positive role in prolonging the service life of pavement. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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20 pages, 2167 KiB

Open AccessArticle

One-Step Lignin Refining Process: The Influence of the Solvent Nature on the Properties and Quality of Fractions

by Oihana Gordobil, René Herrera Diaz, Jakub Sandak and Anna Sandak

Polymers 2022, 14(12), 2363; https://doi.org/10.3390/polym14122363 - 11 Jun 2022

Cited by 7 | Viewed by 2946

Abstract

Heterogeneity of kraft lignin is one of the main limitations for the development of high-performance applications. Therefore, refining lignin using organic solvents is a promising strategy to obtain homogenous fractions with controlled quality in terms of structure and properties. In this work, one-step refining processes for hardwood kraft lignin using nine organic solvents of different chemical nature and polarity were carried out with the aim of investigating and understanding the effect of the type of organic solvent on the quality of resulting fractions. Structural features of both soluble and insoluble lignin fractions were assessed by GPC, Py-GC-MS, and FTIR linked to PCA analysis. Moreover, functional properties such as physical appearance, hygroscopicity, antioxidant capacity, and thermal properties were evaluated. The results evidenced the relationship between the nature and polarity of the solvents and the properties of the obtained soluble and insoluble fractions. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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15 pages, 3688 KiB

Open AccessArticle

Mass Transport of Lignin in Confined Pores

by Roujin Ghaffari, Henrik Almqvist, Robin Nilsson, Gunnar Lidén and Anette Larsson

Polymers 2022, 14(10), 1993; https://doi.org/10.3390/polym14101993 - 13 May 2022

Cited by 7 | Viewed by 2332

Abstract

A crucial step in the chemical delignification of wood is the transport of lignin fragments into free liquor; this step is believed to be the rate-limiting step. This study has investigated the diffusion of kraft lignin molecules through model cellulose membranes of various pore sizes (1–200 nm) by diffusion cells, where the lignin molecules diffuse from donor to acceptor cells through a membrane, where diffusion rate increases by pore size. UV–vis spectra of the donor solutions showed greater absorbance at higher wavelengths (~450 nm), which was probably induced by scattering due to presence of large molecules/clusters, while acceptor samples passed through small pore membranes did not. The UV–vis spectra of acceptor solutions show a characteristic peak at around 350 nm, which corresponds to ionized conjugated molecules: indicating that a chemical fractionation has occurred. Size exclusion chromatography (SEC) showed a difference in the molecular weight (M_w) distribution between lignin from the donor and acceptor chambers. The results show that small pore sizes enable the diffusion of small individual molecules and hinder the transport of large lignin molecules or possible lignin clusters. This study provides more detail in understanding the mass transfer events of pulping processes. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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11 pages, 1601 KiB

Open AccessArticle

Study of Lignin Extracted from Rubberwood Using Microwave Assisted Technology for Fuel Additive

by Trakarn Yimtrakarn, Watchareeya Kaveevivitchai, Wen-Chien Lee and Nuttapol Lerkkasemsan

Polymers 2022, 14(4), 814; https://doi.org/10.3390/polym14040814 - 20 Feb 2022

Cited by 9 | Viewed by 8267

Abstract

Lignin is the most abundant natural aromatic polymer, especially in plant biomass. Lignin-derived phenolic compounds can be processed into high-value liquid fuel. This study aimed to determine the yield of lignin by the microwave-assisted solvent extraction method and to characterize some essential properties of the extracted lignin. Rubberwood sawdust (Hevea brasiliensis) was extracted for lignin with an organic-based solvent, either ethanol or isopropanol, in a microwave oven operating at 2450 MHz. Two levels of power of microwave, 100 W and 200 W, were tested as well as five extraction times (5, 10, 15, 20, 25, and 30 min). The extracted lignin was characterized by Klason lignin, Fourier transform infrared spectroscopy (FT-IR), 2D HSQC NMR, Ultraviolet-visible spectrophotometry (UV-vis), and Bomb calorimeter. The results showed that the yield of extracted lignin increased with the extraction time and power of the microwave. In addition, the extraction yield with ethanol was higher than the yield with isopropanol. The highest yield was 6.26 wt.%, with ethanol, 30 min extraction time, and 200 W microwave power. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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12 pages, 1610 KiB

Open AccessArticle

Silica Nanoparticles from Coir Pith Synthesized by Acidic Sol-Gel Method Improve Germination Economics

by Josef Maroušek, Anna Maroušková, Rajiv Periakaruppan, G. M. Gokul, Ananthan Anbukumaran, Andrea Bohatá, Pavel Kříž, Jan Bárta, Pavel Černý and Pavel Olšan

Polymers 2022, 14(2), 266; https://doi.org/10.3390/polym14020266 - 10 Jan 2022

Cited by 66 | Viewed by 3776

Abstract

Lignin is a natural biopolymer. A vibrant and rapid process in the synthesis of silica nanoparticles by consuming the lignin as a soft template was carefully studied. The extracted biopolymer from coir pith was employed as capping and stabilizing agents to fabricate the silica nanoparticles (_nSi). The synthesized silica nanoparticles (_nSi) were characterized by ultraviolet–visible (UV–Vis) spectrophotometry, X-ray diffraction analysis (XRD), Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Analysis (EDAX), Dynamic Light Scattering (DLS) and Fourier-Transform Infrared Spectroscopy (FTIR). All the results obtained jointly and independently verified the formation of silica nanoparticles. In addition, EDAX analysis confirmed the high purity of the _nSi composed only of Si and O, with no other impurities. XRD spectroscopy showed the characteristic diffraction peaks for _nSi and confirmed the formation of an amorphous nature. The average size of _nSi obtained is 18 nm. The surface charge and stability of _nSi were analyzed by using the dynamic light scattering (DLS) and thus revealed that the _nSi samples have a negative charge (−20.3 mV). In addition, the seed germination and the shoot and root formation on Vigna unguiculata were investigated by using the _nSi. The results revealed that the application of _nSi enhanced the germination in V. unguiculata. However, further research studies must be performed in order to determine the toxic effect of biogenic _nSi before mass production and use of agricultural applications. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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14 pages, 1871 KiB

Open AccessArticle

Assessment of the Efficiency of Chemical and Thermochemical Depolymerization Methods for Lignin Valorization: Principal Component Analysis (PCA) Approach

by Khaled Younes, Ahmad Moghrabi, Sara Moghnie, Omar Mouhtady, Nimer Murshid and Laurent Grasset

Polymers 2022, 14(1), 194; https://doi.org/10.3390/polym14010194 - 4 Jan 2022

Cited by 13 | Viewed by 2668

Abstract

Energy demand and the use of commodity consumer products, such as chemicals, plastics, and transportation fuels, are growing nowadays. These products, which are mainly derived from fossil resources and contribute to environmental pollution and CO2 emissions, will be used up eventually. Therefore, a renewable inexhaustible energy source is required. Plant biomass resources can be used as a suitable alternative source due to their green, clean attributes and low carbon emissions. Lignin is a class of complex aromatic polymers. It is highly abundant and a major constituent in the structural cell walls of all higher vascular land plants. Lignin can be used as an alternative source for fine chemicals and raw material for biofuel production. There are many chemical processes that can be potentially utilized to increase the degradation rate of lignin into biofuels or value-added chemicals. In this study, two lignin degradation methods, CuO–NaOH oxidation and tetramethyl ammonium hydroxide (TMAH) thermochemolysis, will be addressed. Both methods showed a high capacity to produce a large molecular dataset, resulting in tedious and time-consuming data analysis. To overcome this issue, an unsupervised machine learning technique called principal component analysis (PCA) is implemented. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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Review

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18 pages, 43571 KiB

Open AccessReview

Fluorescence Microscopy Methods for the Analysis and Characterization of Lignin

by Agustín Maceda and Teresa Terrazas

Polymers 2022, 14(5), 961; https://doi.org/10.3390/polym14050961 - 28 Feb 2022

Cited by 25 | Viewed by 6015

Abstract

Lignin is one of the most studied and analyzed materials due to its importance in cell structure and in lignocellulosic biomass. Because lignin exhibits autofluorescence, methods have been developed that allow it to be analyzed and characterized directly in plant tissue and in samples of lignocellulose fibers. Compared to destructive and costly analytical techniques, fluorescence microscopy presents suitable alternatives for the analysis of lignin autofluorescence. Therefore, this review article analyzes the different methods that exist and that have focused specifically on the study of lignin because with the revised methods, lignin is characterized efficiently and in a short time. The existing qualitative methods are Epifluorescence and Confocal Laser Scanning Microscopy; however, other semi-qualitative methods have been developed that allow fluorescence measurements and to quantify the differences in the structural composition of lignin. The methods are fluorescence lifetime spectroscopy, two-photon microscopy, Föster resonance energy transfer, fluorescence recovery after photobleaching, total internal reflection fluorescence, and stimulated emission depletion. With these methods, it is possible to analyze the transport and polymerization of lignin monomers, distribution of lignin of the syringyl or guaiacyl type in the tissues of various plant species, and changes in the degradation of wood by pulping and biopulping treatments as well as identify the purity of cellulose nanofibers though lignocellulosic biomass. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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23 pages, 8731 KiB

Open AccessReview

Lignin-Based Materials for Sustainable Rechargeable Batteries

by Han Young Jung, Jeong Seok Lee, Hyun Taek Han, Jaehan Jung, KwangSup Eom and Jung Tae Lee

Polymers 2022, 14(4), 673; https://doi.org/10.3390/polym14040673 - 10 Feb 2022

Cited by 26 | Viewed by 10312

Abstract

This review discusses important scientific progress, problems, and prospects of lignin-based materials in the field of rechargeable batteries. Lignin, a component of the secondary cell wall, is considered a promising source of biomass. Compared to cellulose, which is the most extensively studied biomass material, lignin has a competitive price and a variety of functional groups leading to broad utilization such as adhesive, emulsifier, pesticides, polymer composite, carbon precursor, etc. The lignin-based materials can also be applied to various components in rechargeable batteries such as the binder, separator, electrolyte, anode, and cathode. This review describes how lignin-based materials are adopted in these five components with specific examples and explains why lignin is attractive in each case. The electrochemical behaviors including charge–discharge profiles, cyclability, and rate performance are discussed between lignin-based materials and materials without lignin. Finally, current limitations and future prospects are categorized to provide design guidelines for advanced lignin-based materials. Full article

(This article belongs to the Special Issue Lignin Based Materials: Structure, Properties and Applications)

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