Polymers

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20 pages, 2026 KiB

Open AccessArticle

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 5399

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

Open AccessArticle

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 3515

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

Open AccessEditor’s ChoiceArticle

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 2526

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

Open AccessArticle

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 5221

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

Open AccessEditor’s ChoiceArticle

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 2680

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

Open AccessEditor’s ChoiceArticle

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 3689

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,

M O R

= 12.61 MPa) and plywood facings (

E

= 1248–1395 MPa,

M O R

= 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

Open AccessEditor’s ChoiceArticle

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 3602

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

Open AccessArticle

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 3469

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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Review

Jump to: Research

21 pages, 883 KiB

Open AccessEditor’s ChoiceReview

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 9431

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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