Recent Developments in Eco-Friendly Wood-Based Composites

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 (31 January 2021) | Viewed by 40548

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Guest Editor
Department of Wood-Based Composites, Cellulose and Paper, Ukrainian National Forestry University, 79057 Lviv, Ukraine
Interests: wood science and technology; wood–polymer composites; lignocellulosic based composites; wood modification; wood bonding
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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

Published Papers (9 papers)

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Research

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20 pages, 2026 KiB  
Article
Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing
by Roman Réh, Ľuboš Krišťák, Ján Sedliačik, Pavlo Bekhta, Monika Božiková, Daniela Kunecová, Vlasta Vozárová, Eugenia Mariana Tudor, Petar Antov and Viktor Savov
Polymers 2021, 13(4), 511; https://doi.org/10.3390/polym13040511 - 8 Feb 2021
Cited by 63 | Viewed by 5386
Abstract
The potential of using ground birch (Betula verrucosa Ehrh.) bark as an eco-friendly additive in urea-formaldehyde (UF) adhesives for plywood manufacturing was investigated in this work. Five-ply plywood panels were fabricated in the laboratory from beech (Fagus sylvatica L.) veneers bonded [...] Read more.
The potential of using ground birch (Betula verrucosa Ehrh.) bark as an eco-friendly additive in urea-formaldehyde (UF) adhesives for plywood manufacturing was investigated in this work. Five-ply plywood panels were fabricated in the laboratory from beech (Fagus sylvatica L.) veneers bonded with UF adhesive formulations comprising three addition levels of birch bark (BB) as a filler (10%, 15%, and 20%). Two UF resin formulations filled with 10% and 20% wheat flour (WF) were used as reference samples. The mechanical properties (bending strength, modulus of elasticity and shear strength) of the laboratory-fabricated plywood panels, bonded with the addition of BB in the adhesive mixture, were evaluated and compared with the European standard requirements (EN 310 and EN 314-2). The mechanical strength of the plywood with the addition of BB in the adhesive mixture is acceptable and met the European standard requirements. Markedly, the positive effect of BB in the UF adhesive mixture on the reduction of formaldehyde emission from plywood panels was also confirmed. Initially, the most significant decrease in formaldehyde release (up to 14%) was measured for the plywood sample, produced with 15% BB. After four weeks, the decrease in formaldehyde was estimated up to 51% for the sample manufactured with 20% BB. The performed differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and derivative thermogravimetry (DTG), also confirmed the findings of the study. As this research demonstrated, BB as a waste or by-product of wood processing industry, can be efficiently utilized as an environmentally friendly, inexpensive alternative to WF as a filler in UF adhesive formulations for plywood manufacturing. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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19 pages, 2602 KiB  
Article
Properties of Thermoplastic-Bonded Plywood: Effects of the Wood Species and Types of the Thermoplastic Films
by Pavlo Bekhta, Marcus Müller and Ilona Hunko
Polymers 2020, 12(11), 2582; https://doi.org/10.3390/polym12112582 - 3 Nov 2020
Cited by 21 | Viewed by 3501
Abstract
There are a lack of proper adhesives that meet the wood industry requirements of being environmentally friendly, low cost, and easy to use; thus, the application of thermoplastic polymers, especially films, is promising. This work expands our knowledge about the possibility of using [...] Read more.
There are a lack of proper adhesives that meet the wood industry requirements of being environmentally friendly, low cost, and easy to use; thus, the application of thermoplastic polymers, especially films, is promising. This work expands our knowledge about the possibility of using thermoplastic films for the production of environmentally friendly plywood. The effects of the adhesives type and wood species on the properties of plastic film bonded plywood were studied. Sliced veneers of two hardwoods (birch and beech) and one softwood (spruce) were used in the experiments. Three types of thermoplastic films—low-density polyethylene (LDPE), co-polyamide (CoPA), and co-polyester (CoPE)—were used as an adhesive for bonding plywood samples. Melamine–urea–formaldehyde (MUF) resin was used as a reference. The influence of the type of adhesive and wood species as well as their interaction on the properties of plywood was significant. The lowest bonding strength demonstrated plywood samples bonded by LDPE, and the highest bonding strength in the samples was shown in those bonded by CoPA. A significant difference was found between softwoods and hardwoods in terms of their influence on the physical and mechanical properties of plywood samples. From the obtained data, it follows that softwoods provide much lower values of bending strength (MOR), modulus of elasticity (MOE), and bonding strength than hardwoods. The obtained bonding strength values of plastic-bonded plywood panels ranged from 1.18 to 2.51 MPa and met the European standard EN 314-2 for Class 1 (dry conditions) plywood. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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11 pages, 4507 KiB  
Article
Effects of SiO2 Filler in the Shell and Wood Fiber in the Core on the Thermal Expansion of Core–Shell Wood/Polyethylene Composites
by Lichao Sun, Haiyang Zhou, Guanggong Zong, Rongxian Ou, Qi Fan, Junjie Xu, Xiaolong Hao and Qiong Guo
Polymers 2020, 12(11), 2570; https://doi.org/10.3390/polym12112570 - 2 Nov 2020
Cited by 10 | Viewed by 2512
Abstract
The influence of nano-silica (nSiO2) and micro-silica (mSiO2) in the shell and wood fiber filler in the core on the thermal expansion behavior of co-extruded wood/polyethylene composites (Co-WPCs) was investigated to optimize the thermal expansion resistance. The cut Co-WPCs [...] Read more.
The influence of nano-silica (nSiO2) and micro-silica (mSiO2) in the shell and wood fiber filler in the core on the thermal expansion behavior of co-extruded wood/polyethylene composites (Co-WPCs) was investigated to optimize the thermal expansion resistance. The cut Co-WPCs samples showed anisotropic thermal expansion, and the thermal expansion strain and linear coefficient of thermal expansion (LCTE) decreased by filling the shell layer with rigid silica, especially nSiO2. Finite element analysis indicated that the polymer-filled shell was mainly responsible for the thermal expansion. The entire Co-WPCs samples exhibited a lower thermal expansion strain than the cut Co-WPCs samples due to protection by the shell. Increasing the wood fiber content in the core significantly decreased the thermal expansion strain and LCTE of the Co-WPCs. The Co-WPCs whose core layer was filled with 70% wood fiber exhibited the greatest anisotropic thermal expansion. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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18 pages, 3652 KiB  
Article
Mechanical, Physical and Thermal Properties of Sugar Palm Nanocellulose Reinforced Thermoplastic Starch (TPS)/Poly (Lactic Acid) (PLA) Blend Bionanocomposites
by A. Nazrin, S. M. Sapuan and M. Y. M. Zuhri
Polymers 2020, 12(10), 2216; https://doi.org/10.3390/polym12102216 - 27 Sep 2020
Cited by 56 | Viewed by 5205
Abstract
In this paper, sugar palm nanocellulose fibre-reinforced thermoplastic starch (TPS)/poly (lactic acid) (PLA) blend bionanocomposites were prepared using melt blending and compression moulding with different TPS concentrations (20%, 30%, 40%, 60%, and 80%) and constant sugar palm nanocellulose fibres (0.5%). The physical, mechanical, [...] Read more.
In this paper, sugar palm nanocellulose fibre-reinforced thermoplastic starch (TPS)/poly (lactic acid) (PLA) blend bionanocomposites were prepared using melt blending and compression moulding with different TPS concentrations (20%, 30%, 40%, 60%, and 80%) and constant sugar palm nanocellulose fibres (0.5%). The physical, mechanical, thermal, and water barrier properties were investigated. The SEM images indicated different TPS loading effects with the morphology of the blend bionanocomposites due to their immiscibility. A high content of TPS led to agglomeration, while a lower content resulted in the presence of cracks and voids. The 20% TPS loading reduced the tensile strength from 49.08 to 19.45 MPa and flexural strength from 79.60 to 35.38 MPa. The thermal stability of the blend bionanocomposites was reduced as the TPS loading increased. The thickness swelling, which corresponded to the water absorption, demonstrated an increasing trend with the increased addition of TPS loading. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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8 pages, 1970 KiB  
Article
Tensile Strength and Moisture Absorption of Sugar Palm-Polyvinyl Butyral Laminated Composites
by Shamsudin N. Syaqira S, Z. Leman, S. M. Sapuan, T. T. Dele-Afolabi, M. A. Azmah Hanim and Budati S.
Polymers 2020, 12(9), 1923; https://doi.org/10.3390/polym12091923 - 26 Aug 2020
Cited by 13 | Viewed by 2670
Abstract
Natural fiber reinforced composites have had a great impact on the development of eco-friendly industrial products for several engineering applications. Sugar palm fiber (SPF) is one of the newly found natural fibers with limited experimental investigation. In the present work, sugar palm fiber [...] Read more.
Natural fiber reinforced composites have had a great impact on the development of eco-friendly industrial products for several engineering applications. Sugar palm fiber (SPF) is one of the newly found natural fibers with limited experimental investigation. In the present work, sugar palm fiber was employed as the natural fiber reinforcement. The composites were hot compressed with polyvinyl butyral (PVB) to form the structure of laminated composites and then were subjected to tensile testing and moisture absorption. The maximum modulus and tensile strength of 0.84 MPa and 1.59 MPa were registered for samples PVB 80-S and PVB 70-S, respectively. Subsequently, the latter exhibited the highest tensile strain at a maximum load of 356.91%. The moisture absorption test revealed that the samples exhibited better water resistance as the proportion of PVB increased relative to the proportion of SPF due to the remarkable hydrophobic property of PVB in comparison with that of SPF. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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15 pages, 7347 KiB  
Article
Bending Behavior of Lightweight Wood-Based Sandwich Beams with Auxetic Cellular Core
by Krzysztof Peliński and Jerzy Smardzewski
Polymers 2020, 12(8), 1723; https://doi.org/10.3390/polym12081723 - 31 Jul 2020
Cited by 23 | Viewed by 3678
Abstract
The work concerns a three-point bending test of beams made of plywood, high density fibre boards, cardboard, and wood-epoxy mass. The goal of the investigation was to determine the effect of thickness and type of wood-based facings on stiffness, strength, ability to absorb, [...] Read more.
The work concerns a three-point bending test of beams made of plywood, high density fibre boards, cardboard, and wood-epoxy mass. The goal of the investigation was to determine the effect of thickness and type of wood-based facings on stiffness, strength, ability to absorb, and dissipate the energy of sandwich beams with an auxetic core. The cognitive goal of the work was to demonstrate the possibility of using recycled materials for facings and cores instead of popular wood composites. Experimental studies and numerical calculations were performed on correctly calibrated models. Experimental studies have shown that the beams with HDF facings (E = 1528 MPa, MOR = 12.61 MPa) and plywood facings (E = 1248–1395 MPa, MOR = 8.34–10.40 MPa) have the most favourable mechanical properties. Beams with plywood facings also have a good ability to absorb energy (1.380–1.746 J), but, in this respect, the beams manufactured of HDF (2.223 J) exhibited better capacity. The use of an auxetic core and facings of plywood and cardboard significantly reduces the amount of dissipated energy (0.0093 J, 0.0067 J). Therefore, this type of structures can be used for modeling beams carrying high deflections. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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12 pages, 924 KiB  
Article
Potential Use of Wollastonite as a Filler in UF Resin Based Medium-Density Fiberboard (MDF)
by Hamid R. Taghiyari, Ayoub Esmailpour, Roya Majidi, Jeffrey J. Morrell, Mohammad Mallaki, Holger Militz and Antonios N. Papadopoulos
Polymers 2020, 12(7), 1435; https://doi.org/10.3390/polym12071435 - 27 Jun 2020
Cited by 23 | Viewed by 3595
Abstract
Urea-formaldehyde (UF) resins are primary petroleum-based, increasing their potential environmental footprint. Identifying additives to reduce the total amount of resin needed without adversely affecting the panel properties could reduce these impacts. Wollastonite is a mineral containing calcium and silica that has been used [...] Read more.
Urea-formaldehyde (UF) resins are primary petroleum-based, increasing their potential environmental footprint. Identifying additives to reduce the total amount of resin needed without adversely affecting the panel properties could reduce these impacts. Wollastonite is a mineral containing calcium and silica that has been used as an additive in a variety of materials and may be useful as a resin extender. Nanoscale wollastonite has been shown to enhance the panel properties but is costly. Micron-scale wollastonite may be a less costly alternative. Medium-density fiberboards were produced by blending a hardwood furnish with UF alone, micron-sized wollastonite alone, or a 9:1 ratio of UF to wollastonite. Panels containing of only wollastonite had poor properties, but the properties of panels with 9:1 UF/wollastonite were similar to the UF-alone panels, except for the internal bond strength. The results suggest that small amounts of micron-sized wollastonite could serve as a resin extender. Further studies are suggested to determine if the micron-sized material has similar positive effects on the resin curing rate. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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11 pages, 2811 KiB  
Article
Some Properties of Composite Drone Blades Made from Nanosilica Added Epoxidized Natural Rubber
by Sunisa Suchat, Aunnuda Lanna, Aujchariya Chotikhun and Salim Hiziroglu
Polymers 2020, 12(6), 1293; https://doi.org/10.3390/polym12061293 - 5 Jun 2020
Cited by 8 | Viewed by 3460
Abstract
The objective of this study was to investigate the basic properties of composite materials that were made from epoxidized natural rubber and nanosilica to be used as blades for drones. Nanocomposite samples were prepared with 5% of epoxidized natural rubber and epoxy resin [...] Read more.
The objective of this study was to investigate the basic properties of composite materials that were made from epoxidized natural rubber and nanosilica to be used as blades for drones. Nanocomposite samples were prepared with 5% of epoxidized natural rubber and epoxy resin loaded with 3% nanosilica. Their resistance against accelerated weathering conditions as well as mechanical properties, including flexural strength, impact strength, and hardness, were evaluated. Based on the findings of this work, the impact strength of the samples decreased 13.33% and 33.33% as a result of exposing them to weathering by UV radiation for 168 h and 336 h, respectively. However, their tensile strength properties enhanced 35.71% and 19.05% for the above corresponding exposure time spars. Experimental composite samples that were made in this study would have great potential to be used as raw material for propeller blade for drones based on their properties evaluated within the scope of this work. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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21 pages, 883 KiB  
Review
A Review on Citric Acid as Green Modifying Agent and Binder for Wood
by Seng Hua Lee, Paridah Md Tahir, Wei Chen Lum, Li Peng Tan, Paiman Bawon, Byung-Dae Park, Syeed SaifulAzry Osman Al Edrus and Ummi Hani Abdullah
Polymers 2020, 12(8), 1692; https://doi.org/10.3390/polym12081692 - 29 Jul 2020
Cited by 57 | Viewed by 9403
Abstract
Citric acid (CA) can be found naturally in fruits and vegetables, particularly citrus fruit. CA is widely used in many fields but its usage as a green modifying agent and binder for wood is barely addressed. Esterification is one of the most common [...] Read more.
Citric acid (CA) can be found naturally in fruits and vegetables, particularly citrus fruit. CA is widely used in many fields but its usage as a green modifying agent and binder for wood is barely addressed. Esterification is one of the most common chemical reactions applied in wood modification. CA contains three carboxyl groups, making it possible to attain at least two esterification reactions that are required for crosslinking when reacting with the hydroxyl groups of the cell wall polymers. In addition, the reaction could form ester linkages to bring adhesivity and good bonding characteristics, and therefore CA could be used as wood binder too. This paper presents a review concerning the usage of CA as a wood modifying agent and binder. For wood modification, the reaction mechanism between wood and CA and the pros and cons of using CA are discussed. CA and its combination with various reactants and their respective optimum parameters are also compiled in this paper. As for the major wood bonding component, the bonding mechanism and types of wood composites bonded with CA are presented. The best working conditions for the CA in the fabrication of wood-based panels are discussed. In addition, the environmental impacts and future outlook of CA-treated wood and bonded composite are also considered. Full article
(This article belongs to the Special Issue Recent Developments in Eco-Friendly Wood-Based Composites)
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