Recent Developments in Eco-Friendly Wood-Based Composites II

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biomacromolecules, Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (5 February 2023) | Viewed by 46690

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Special Issue Editor

Special Issue Information

Dear Colleagues,

Traditional wood-based composites are bonded with synthetic formaldehyde-based adhesives. These adhesives bring certain environmental problems because they release formaldehyde emissions, which is a human carcinogen and toxic for the environment. It is hardly possible to find new uses or new fields for wood-based products because of the lack of proper adhesives to meet wood industry requirements of being eco-friendly, low-cost, and easy to use. That is why the growing ecological and environmental consciousness drives efforts for the development of new eco-friendly wood-based composites for various end-use applications. In recent years, significant efforts have been made to reduce formaldehyde emissions from wood-based composites via the reduction of formaldehyde content in resin formulation; the use of scavengers, such as tannins, lignin, starch, wheat flour, and rice husk flour or other compounds (starch derivatives, charcoal, pozzolan, zeolites, and urea) that scavenge formaldehyde; and post-treatment or surface treatment of the wood-based products and use of natural resins, including soy protein, tannin, lignin, and starch adhesives. One of the possible directions is the creation of wood composites based on environmentally friendly products, where thermoplastics (polyethylene, polypropylene, poly(vinyl chloride) and their copolymers are used as adhesives. Another alternative to the use of synthetic formaldehyde-based adhesives is to manufacture binderless wood composites since wood is a natural polymer material which is rich in lignocellulosic compounds such as cellulose, hemicellulose, and lignin.

The aim of this Special Issue is to collect of original research and reviews focused on laboratory- and industrial-scale solutions to the sustainable development of novel and eco-friendly wood-based composites.

Prof. Ing. Pavlo Bekhta, DrSc.
Guest Editor

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Keywords

  • Eco-friendly wood-based composites
  • Lignocellulosic based composites
  • Wood–polymer composites
  • Biodegradable polymers
  • Thermoplastic polymers
  • Modified formaldehyde-based adhesives
  • Binderless wood-based composites
  • Formaldehyde scavengers
  • Post-treatment of wood composites
  • Surface treatment of wood composites
  • Wood modification
  • Biocomposites
  • Biopolymers
  • Nanotechnology and nanomaterials

Published Papers (13 papers)

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Editorial

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6 pages, 230 KiB  
Editorial
Recent Developments in Eco-Friendly Wood-Based Composites II
by Pavlo Bekhta
Polymers 2023, 15(8), 1941; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15081941 - 19 Apr 2023
Cited by 1 | Viewed by 3212
Abstract
Traditional wood-based composites are bonded with synthetic formaldehyde-based adhesives [...] Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)

Research

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14 pages, 4237 KiB  
Article
Fabrication and Characterization of EVA Resins as Adhesives in Plywood
by Yu Zhang, Ye He, Jiayan Yu, Yuxin Lu, Xinhao Zhang and Lu Fang
Polymers 2023, 15(8), 1834; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15081834 - 10 Apr 2023
Cited by 7 | Viewed by 1639
Abstract
The practical problem of free formaldehyde pollution in the plywood industry is that polyethylene films have been shown to be able to replace some urea–formaldehyde resins for wood adhesives. To broaden the variety of thermoplastic plywood, reduce the hot-press temperature, and save energy [...] Read more.
The practical problem of free formaldehyde pollution in the plywood industry is that polyethylene films have been shown to be able to replace some urea–formaldehyde resins for wood adhesives. To broaden the variety of thermoplastic plywood, reduce the hot-press temperature, and save energy consumption, an ethylene–vinyl acetate (EVA) film was selected as a wood adhesive to manufacture a novel wood–plastic composite plywood via hot-press and secondary press processes. The effects of the hot-press and secondary press processes at different levels on the physical–mechanical properties of EVA plywood (tensile shear strength, 24 h water absorption, and immersion peel performance) were evaluated. The results showed that the properties of the resulting plywood using the EVA film as an adhesive could meet the type III plywood standard. The optimum hot-press time was 1 min/mm, the hot-press temperature was 110–120 °C, the hot-press pressure was 1 MPa, the dosage film was 163 g/m2, the secondary press time was 5 min, the secondary press pressure was 0.5 MPa, and the secondary press temperature was 25 °C. EVA plywood can be used in indoor environments. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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9 pages, 4094 KiB  
Article
Multi-Scale Evaluation of the Effect of Thermal Modification on Chemical Components, Dimensional Stability, and Anti-Mildew Properties of Moso Bamboo
by Xiao Xiao, Xingyu Liang, Haozhe Peng, Kaili Wang, Xiaorong Liu and Yanjun Li
Polymers 2022, 14(21), 4677; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14214677 - 02 Nov 2022
Cited by 5 | Viewed by 1198
Abstract
By promoting greenhouse gas sequestration, bamboo and bamboo-based products can improve carbon storage, and thus help decrease greenhouses gas emission through replacing traditional products like concrete, steel, and alloy. Thermal modification is a useful way to effectively enhance the dimensional stability and mold-resistance [...] Read more.
By promoting greenhouse gas sequestration, bamboo and bamboo-based products can improve carbon storage, and thus help decrease greenhouses gas emission through replacing traditional products like concrete, steel, and alloy. Thermal modification is a useful way to effectively enhance the dimensional stability and mold-resistance property of bamboo and bamboo-based products compared with chemical treatment. This work investigates the change in anti-mildew properties, micro-structure, and chemical composition of bamboo after heat treatment. Saturated steam heat treatment was applied for this project. SEM results showed that the structural damage of parenchyma cells resulted in the separation of thin-walled cells and vascular bundles. Thus, the original regular structure of bamboo, characterized by plump and intact cells, changed markedly. After thermal modification, bamboo samples exhibited improved dimensional stability and anti-fungal properties due to the decrement of hemicellulose and cellulose. The hardness and MOE of the modified bamboo were 0.75 and 20.6 GPa, respectively. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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14 pages, 3331 KiB  
Article
Effects of Wood Particles from Deadwood on the Properties and Formaldehyde Emission of Particleboards
by Pavlo Bekhta, Ruslan Kozak, Vladimír Gryc, Václav Sebera and Jan Tippner
Polymers 2022, 14(17), 3535; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14173535 - 28 Aug 2022
Cited by 4 | Viewed by 1295
Abstract
The volume of deadwood increases annually because of changes in environmental, climatic, and hydrological conditions. On the other hand, during the last decade, manufacturers of wood-based boards have been facing an acute problem of a shortage of conventional raw materials. The purpose of [...] Read more.
The volume of deadwood increases annually because of changes in environmental, climatic, and hydrological conditions. On the other hand, during the last decade, manufacturers of wood-based boards have been facing an acute problem of a shortage of conventional raw materials. The purpose of this study was to evaluate the possibility of using wood particles from deadwood in the production of particleboards. Three-layer particleboards with different content of deadwood particles (0%, 25%, 50%, 75%, 100%) were produced. Conventional urea-formaldehyde (UF) resin was used for gluing the particles. The physical and mechanical properties of the boards, as well as the formaldehyde content in the boards, were determined. In addition, the effect of adding melamine-urea-formaldehyde (MUF) resin to UF adhesive on the properties of the boards was investigated. Replacing conventional sound wood particles with deadwood particles leads to deterioration of the physical and mechanical properties of the boards. The boards from deadwood particles absorb more water and swell more. The bending strength (MOR), modulus of elasticity in bending (MOE), and internal bonding (IB) values for boards with 100% deadwood particles are reduced by 26.5%, 23.1%, and 72.4%, respectively, compared to reference boards from sound wood particles. Despite this, a significant advantage is that boards made from 100% deadwood particles are characterized by 34.5% less formaldehyde content than reference boards made from conventional sound wood. Moreover, adding 3% of MUF resin to UF adhesive increases MOR, MOE, and IB by 44.1%, 43.3%, and 294.4%, respectively. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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23 pages, 92978 KiB  
Article
Properties Enhancement Nano Coconut Shell Filled in Packaging Plastic Waste Bionanocomposite
by Ismail Ismail, Quratul Aini, Zulkarnain Jalil, Niyi Gideon Olaiya, Mursal Mursal, C.K. Abdullah and Abdul Khalil H.P.S.
Polymers 2022, 14(4), 772; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14040772 - 16 Feb 2022
Cited by 6 | Viewed by 3757
Abstract
Plastic waste recycling has been proposed as a long-term solution to eliminate land and marine deposit. This study proposed a new approach to fabricate biocomposites of nano-sized fillers and low matrix compositions with a great performance by using plastic packaging waste different from [...] Read more.
Plastic waste recycling has been proposed as a long-term solution to eliminate land and marine deposit. This study proposed a new approach to fabricate biocomposites of nano-sized fillers and low matrix compositions with a great performance by using plastic packaging waste different from the conventional biocomposite. Coconut shell, an agricultural waste, was bonden with waste plastic to form a biocomposite with a coupling agent. The optimum percentage composition and the effect of coconut shell ball milling time on the properties of the biocomposite were studied with density, thickness swelling, porosity flexural strength, flexural modulus, compressive strength, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscope (SEM), and atomic force microscopy (AFM). The results showed that the optimum performance of biocomposite was obtained at 30/70 (wt.%) plastic waste to coconut shell ratio, where 70 wt.% was the highest coconut shell composition that can be achieved. Furthermore, for 30 wt.% of polypropylene (low matrix), the performance of biocomposite improved significantly with milling time due to enhanced interaction between filler and matrix. As the milling time was increased from 0 to 40 h, the density increased from 0.9 to 1.02 g/cm3; thickness swelling decreased from 3.4 to 1.8%; porosity decreased from 7.0 to 3.0%; flexural strength increased from 8.19 to 12.26 MPa; flexural modulus increased from 1.67 to 2.87 GPa, and compressive strength increased from 16.00 to 27.20 MPa. The degradation temperature of biocomposite also increased as the milling duration increased from 0 to 40 h. The melting temperature increased significantly from 160 to 170 °C as the milling duration increased from 0 to 40 h. The depolymerisation occurred at 350 °C, which also increased with milling duration. This study revealed that the performance of biocomposite improved significantly with a lower percentage matrix and fillernanoparticle rather than increasing the percentage of the matrix. The nanocomposite can be used as a panelboard in industrial applications. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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13 pages, 2045 KiB  
Article
Selected Properties of Plywood Bonded with Low-Density Polyethylene Film from Different Wood Species
by Pavlo Bekhta, Orest Chernetskyi, Iryna Kusniak, Nataliya Bekhta and Olesya Bryn
Polymers 2022, 14(1), 51; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14010051 - 23 Dec 2021
Cited by 8 | Viewed by 2758
Abstract
In this work, the effects of wood species and thickness of low-density polyethylene (LDPE) film on the properties of environmentally-friendly plywood were studied. Rotary-cut veneers from four wood species (beech, birch, hornbeam and poplar) and LDPE film of four thicknesses (50, 80, 100 [...] Read more.
In this work, the effects of wood species and thickness of low-density polyethylene (LDPE) film on the properties of environmentally-friendly plywood were studied. Rotary-cut veneers from four wood species (beech, birch, hornbeam and poplar) and LDPE film of four thicknesses (50, 80, 100 and 150 µm) as an adhesive were used for making plywood samples. The findings of this study demonstrated that plywood samples using all the investigated wood species bonded with LDPE film showed satisfactory physical–mechanical properties. Poplar veneer provided the lowest values for bending strength, modulus of elasticity and thickness swelling of all the plywood samples, but the bonding strength was at the same level as birch and hornbeam veneer. Beech plywood samples had the best mechanical properties. An increase in LDPE film thickness improved the physical–mechanical properties of plastic-bonded plywood. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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21 pages, 4708 KiB  
Article
Properties of Low-Cost WPCs Made from Alien Invasive Trees and rLDPE for Interior Use in Social Housing
by Abubakar Sadiq Mohammed and Martina Meincken
Polymers 2021, 13(15), 2436; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13152436 - 24 Jul 2021
Cited by 9 | Viewed by 2620
Abstract
Low-cost wood–plastic composites (WPCs) were developed from invasive trees and recycled low-density polyethylene. The aim was to produce affordable building materials for low-cost social housing in South Africa. Both raw materials are regarded as waste materials, and the subsequent product development adds value [...] Read more.
Low-cost wood–plastic composites (WPCs) were developed from invasive trees and recycled low-density polyethylene. The aim was to produce affordable building materials for low-cost social housing in South Africa. Both raw materials are regarded as waste materials, and the subsequent product development adds value to the resources, while simultaneously reducing the waste stream. The production costs were minimised by utilising the entire biomass of Acacia saligna salvaged from clearing operations without any prior processing, and low-grade recycled low-density polyethylene to make WPCs without any additives. Different biomass/plastic ratios, particle sizes, and press settings were evaluated to determine the optimum processing parameters to obtain WPCs with adequate properties. The water absorption, dimensional stability, modulus of rupture, modulus of elasticity, tensile strength, and tensile moduli were improved at longer press times and higher temperatures for all blending ratios. This has been attributed to the crystallisation of the lignocellulose and thermally induced cross-linking in the polyethylene. An increased biomass ratio and particle size were positively correlated with water absorption and thickness swelling and inversely related with MOR, tensile strength, and density due to an incomplete encapsulation of the biomass by the plastic matrix. This study demonstrates the feasibility of utilising low-grade recycled polyethylene and the whole-tree biomass of A. saligna, without the need for pre-processing and the addition of expensive modifiers, to produce WPCs with properties that satisfy the minimum requirements for interior cladding or ceiling material. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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11 pages, 3030 KiB  
Article
Binderless Thermal Insulation Panels Made of Spruce Bark Fibres
by Jakob Gößwald, Marius-Cătălin Barbu, Alexander Petutschnigg and Eugenia Mariana Tudor
Polymers 2021, 13(11), 1799; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13111799 - 29 May 2021
Cited by 21 | Viewed by 2520
Abstract
Tree bark is a by-product of the timber industry available in large amounts, considering that approximately 10% of the volume of a tree stem is bark. Bark is used primarily for low-value applications such as heat generation or as mulch. To the best [...] Read more.
Tree bark is a by-product of the timber industry available in large amounts, considering that approximately 10% of the volume of a tree stem is bark. Bark is used primarily for low-value applications such as heat generation or as mulch. To the best of our knowledge, this study is the first one that scrutinises thermal insulation panels made from spruce bark fibres with different densities and fibre lengths manufactured in a wet process. The insulation boards with densities between 160 and 300 kg/m3 were self-bonded. Internal bond, thermal conductivity, and dimensional stability (thickness swelling and water absorption), together with formaldehyde content, were analysed. The thermal properties of the boards were directly correlated with the density and reached about 0.044 W/m*K, while the internal bond was rather influenced by the fibre length and was relatively low (on average 0.07 N/mm2). The water absorption was high (from 55% to 380%), while the thickness swelling remained moderate (up to 23%). The results of this study have shown that widely available bark residues can be successfully utilised as an innovative raw material for efficient eco-friendly thermal insulation products. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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Review

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22 pages, 1677 KiB  
Review
Panel Products Made of Oil Palm Trunk: A Review of Potency, Environmental Aspect, and Comparison with Wood-Based Composites
by Arif Nuryawan, Jajang Sutiawan, Rahmawaty, Nanang Masruchin and Pavlo Bekhta
Polymers 2022, 14(9), 1758; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14091758 - 26 Apr 2022
Cited by 9 | Viewed by 3882
Abstract
Oil palm plantations have expanded rapidly in Southeast Asia, particularly in Indonesia and Malaysia. A lot of products, including food and other edible products, oleo-chemicals, cosmetics, personal and household care, pharmaceutical products, and biodiesels are derived from palm oil, thus making them one [...] Read more.
Oil palm plantations have expanded rapidly in Southeast Asia, particularly in Indonesia and Malaysia. A lot of products, including food and other edible products, oleo-chemicals, cosmetics, personal and household care, pharmaceutical products, and biodiesels are derived from palm oil, thus making them one of the most economically important plants. After 25–30 years of age, the palms are felled and replaced due to declining oil production. Oil palm trunks (OPT) are considered significant waste products. The trunks remain on the plantation site for nutrient recycling or burning. This increases insect and fungi populations causing environmental problems for the new palm generation or air pollution due to the fire. Up till now, OPT has received less attention in research studies. Therefore, this review summarizes the utilization of OPT into products made of oil palm fibers mainly derived from OPT and its application as the substitution of wood panel products. Some research works have been carried out on oil palm fibers that are derived from OPT for exploiting their potential as raw material of composite panel products, which is the objective of this review. Areas of development are processed into various conventional composite panel products such as plywood and laminated board which are usually predominantly made of wood and bonded by synthetic resins, particleboard with binder, or binderless and cement board which is arranged with wood as a minor component. All of the products have been presented and described technically according to best knowledge of the authors and literature review. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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22 pages, 6739 KiB  
Review
Recent Progress in Modification Strategies of Nanocellulose-Based Aerogels for Oil Absorption Application
by M. A. Iskandar, Esam Bashir Yahya, H. P. S. Abdul Khalil, A. A. Rahman and M. A. Ismail
Polymers 2022, 14(5), 849; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14050849 - 22 Feb 2022
Cited by 31 | Viewed by 4337
Abstract
Oil spills and oily wastewater have become a major environmental problem in recent years, directly impacting the environment and biodiversity. Several techniques have been developed to solve this problem, including biological degradation, chemicals, controlled burning, physical absorption and membrane separation. Recently, biopolymeric aerogels [...] Read more.
Oil spills and oily wastewater have become a major environmental problem in recent years, directly impacting the environment and biodiversity. Several techniques have been developed to solve this problem, including biological degradation, chemicals, controlled burning, physical absorption and membrane separation. Recently, biopolymeric aerogels have been proposed as a green solution for this problem, and they possess superior selective oil absorption capacity compared with other approaches. Several modification strategies have been applied to nanocellulose-based aerogel to enhance its poor hydrophobicity, increase its oil absorption capacity, improve its selectivity of oils and make it a compressible and elastic magnetically responsive aerogel, which will ease its recovery after use. This review presents an introduction to nanocellulose-based aerogel and its fabrication approaches. Different applications of nanocellulose aerogel in environmental, medical and industrial fields are presented. Different strategies for the modification of nanocellulose-based aerogel are critically discussed in this review, presenting the most recent works in terms of enhancing the aerogel performance in oil absorption in addition to the potential of these materials in near future. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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35 pages, 2529 KiB  
Review
A Critical Review on Wood-Based Polymer Composites: Processing, Properties, and Prospects
by Manickam Ramesh, Lakshminarasimhan Rajeshkumar, Ganesan Sasikala, Devarajan Balaji, Arunachalam Saravanakumar, Venkateswaran Bhuvaneswari and Ramasamy Bhoopathi
Polymers 2022, 14(3), 589; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14030589 - 31 Jan 2022
Cited by 55 | Viewed by 10665
Abstract
Waste recycling is one of the key aspects in current day studies to boost the country’s circular economy. Recycling wood from construction and demolished structures and combining it with plastics forms wood-polymer composites (WPC) which have a very wide scope of usage. Such [...] Read more.
Waste recycling is one of the key aspects in current day studies to boost the country’s circular economy. Recycling wood from construction and demolished structures and combining it with plastics forms wood-polymer composites (WPC) which have a very wide scope of usage. Such recycled composites have very low environmental impact in terms of abiotic potential, global warming potential, and greenhouse potential. Processing of WPCs can be easily done with predetermined strength values that correspond to its end application. Yet, the usage of conventional polymer composite manufacturing techniques such as injection molding and extrusion has very limited scope. Many rheological characterization techniques are being followed to evaluate the influence of formulation and process parameters over the quality of final WPCs. It will be very much interesting to carry out a review on the material formulation of WPCs and additives used. Manufacturing of wood composites can also be made by using bio-based adhesives such as lignin, tannin, and so on. Nuances in complete replacement of synthetic adhesives as bio-based adhesives are also discussed by various researchers which can be done only by complete understanding of formulating factors of bio-based adhesives. Wood composites play a significant role in many non-structural and structural applications such as construction, floorings, windows, and door panels. The current review focuses on the processing of WPCs along with additives such as wood flour and various properties of WPCs such as mechanical, structural, and morphological properties. Applications of wood-based composites in various sectors such as automotive, marine, defense, and structural applications are also highlighted in this review. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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12 pages, 1939 KiB  
Review
Research Progress of Wood-Based Panels Made of Thermoplastics as Wood Adhesives
by Xianfeng Mo, Xinhao Zhang, Lu Fang and Yu Zhang
Polymers 2022, 14(1), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14010098 - 28 Dec 2021
Cited by 13 | Viewed by 3486
Abstract
When thermoplastic resins such as polyethylene (PE) and polypropylene (PP) are selected as wood adhesives to bond wood particles (fibers, chips, veneers) by using the hot-pressing technique, the formaldehyde emission issue that has long existed in the wood-based panel industry can be effectively [...] Read more.
When thermoplastic resins such as polyethylene (PE) and polypropylene (PP) are selected as wood adhesives to bond wood particles (fibers, chips, veneers) by using the hot-pressing technique, the formaldehyde emission issue that has long existed in the wood-based panel industry can be effectively solved. In this study, in general, thermoplastic-bonded wood-based panels presented relatively higher mechanical properties and better water resistance and machinability than the conventional urea–formaldehyde resin-bonded wood-based panels. However, the bonding structure of the wood and thermoplastic materials was unstable at high temperatures. Compared with the wood–plastic composites manufactured by the extruding or injection molding methods, thermoplastic-bonded wood-based panels have the advantages of larger size, a wider raw material range and higher production efficiency. The processing technology, bonding mechanism and the performance of thermoplastic-bonded wood-based panels are comprehensively summarized and reviewed in this paper. Meanwhile, the existing problems of this new kind of panel and their future development trends are also highlighted, which can provide the wood industry with foundations and guidelines for using thermoplastics as environmentally friendly adhesives and effectively solving indoor pollution problems. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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29 pages, 3269 KiB  
Review
Lignosulphonates as an Alternative to Non-Renewable Binders in Wood-Based Materials
by Sofia Gonçalves, João Ferra, Nádia Paiva, Jorge Martins, Luísa H. Carvalho and Fernão D. Magalhães
Polymers 2021, 13(23), 4196; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13234196 - 30 Nov 2021
Cited by 17 | Viewed by 3222
Abstract
Lignin is a widely abundant renewable source of phenolic compounds. Despite the growing interest on using it as a substitute for its petroleum-based counterparts, only 1 to 2% of the global lignin production is used for obtaining value-added products. Lignosulphonates (LS), derived from [...] Read more.
Lignin is a widely abundant renewable source of phenolic compounds. Despite the growing interest on using it as a substitute for its petroleum-based counterparts, only 1 to 2% of the global lignin production is used for obtaining value-added products. Lignosulphonates (LS), derived from the sulphite pulping process, account for 90% of the total market of commercial lignin. The most successful industrial attempts to use lignin for wood adhesives are based on using this polymer as a partial substitute in phenol-formaldehyde or urea-formaldehyde resins. Alternatively, formaldehyde-free adhesives with lignin and lignosulphonates have also been developed with promising results. However, the low number of reactive sites available in lignin’s aromatic ring and high polydispersity have hindered its application in resin synthesis. Currently, finding suitable crosslinkers for LS and decreasing the long pressing time associated with lignin adhesives remains a challenge. Thus, several methods have been proposed to improve the reactivity of lignin molecules. In this paper, techniques to extract, characterize, as well as improve the reactivity of LS are addressed. The most recent advances in the application of LS in wood adhesives, with and without combination with formaldehyde, are also reviewed. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites II)
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