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For the production of wood composite materials, adhesives based on cheap and affordable, but harmful urea-formaldehyde resins are mainly used. Given the substantial production volumes of such materials, it is important to find environmental solutions to reduce formaldehyde emissions during their pressing and subsequent operation. The purpose of the study was to present the results of a study on the use of magnesium oxide nanoparticles to bind unreacted formaldehyde in wood composite materials. Analysis of methods for manufacturing metal nanoparticles allowed determining a priority method that allows obtaining ultrafine structures with a size not exceeding 100 nm, namely, the method of volumetric electric spark dispersion of metals in a liquid. Investigating the morphology of magnesium nanoparticles allowed determining that they have an almost crystalline form formed from the vapour phase, with an average particle length not exceeding 100 nm. The results of spectral analysis of the element composition in the nanophase, specifically magnesium and oxygen, demonstrated that the magnesium content does not exceed 32.2%, while oxygen constitutes 67.78%. This indicates that divalent magnesium oxide does not have a pronounced metallic phase, which would interfere with the sorption processes of formaldehyde. The conducted examinations of formaldehyde emission of samples of particle boards with modified magnesium oxide nanoparticles in concentrations of 2% and 8% glue based on urea-formaldehyde resin showed mixed results. Compared to the control samples, the formaldehyde level remained almost unchanged on the second day of follow-up, and for a concentration of 2%, it even increased by 6%. However, by the sixteenth and ninetieth day, a reduction in the level of free formaldehyde emissions was observed at 19% and 22% respectively. The results obtained can be used to improve the production of non-harmful particle boards with improved properties. [ABSTRACT FROM AUTHOR]

The use of polycondensation urea-formaldehyde (UF) resins in the woodworking and furniture industries is widespread due to their relatively low price, high reactivity, availability of raw materials, and ease of use. After curing, they provide a transparent, brittle joint, but their main disadvantage is the continuous emission of formaldehyde. The naturally occurring biopolymer keratin and the amino acid cysteine prepared from sheep wool were chosen and tested as possible agents for UF adhesives, allowing the reduction of formaldehyde emissions from wood-based panels. Emissions of formaldehyde were determined in accordance with EN ISO 12460-4. The gluing quality was tested according to standard EN 314-1, and the tested plywood met the requirements of standard EN 314-2. The most significant decrease in formaldehyde emission by up to 44.0% was achieved by applying 1% MOD-I (pre-condensate of glutaraldehyde and urea + cysteine) to the reference UF adhesive. Therefore, samples prepared for this study have great potential for application as environmentally friendly formaldehyde scavengers. [ABSTRACT FROM AUTHOR]

The effective use of low-grade pine wood (Pinus Sylvestris L.) affected by rot, the volume of which is currently growing mainly due to climate change is proposed in the paper. Pine wood in the form of wood wool was proposed to use as an insulating filling inside the structure of wall panels. Modification of wood wool was carried out with various binders to ensure its biological stability. The experimentally verified calculation of thermal properties confirmed the proposed construction of wood panels with specified insulation, as well the wall thickness fulfils requirements according to building codes for construction engineering. The minimum thickness of the outer walls of frame wooden houses withstanding daily or seasonal temperature fluctuations was determined. [ABSTRACT FROM AUTHOR]

Industrially important properties of wood can be changed due to the modification of birch wood (Betula pendula L.) after the process of thermal treatment with saturated water steam. The birch wood was modified by saturated water steam at 125 ± 2.5 °C for 8 hours and at a pressure of 0.18 MPa. The water contact angle of steam-treated birch wood increased from 42.1° (for untreated birch wood) to 52.4° (for steam-treated birch wood), and the stability of water drop on steam-treated birch wood surface increased. FTIR spectra showed an increase in C=O and glycoside bonds concentration on the surface of steam-treated birch wood, but the concentration of C-O-C groups decreased. XPS measurements confirmed that the concentration of oxygen as well as C=O and C-O-O groups on the surface of steamtreated birch wood showed an increment in comparison with the native wood sample. SEM micro photos confirmed the minor changes of birch wood cells due to the action of saturated water steam modification. [ABSTRACT FROM AUTHOR]

The aim of the presented research was to determine the suitability of both non-modified and modified buckwheat husk (BH) as a filler for urea–formaldehyde adhesive in plywood production. The effect of two modification methods, acetylation and silanization, was investigated. Infrared spectroscopy outcomes confirmed that both acetylation and silanization of the filler had occurred. Based on the results, it was found that the introduction of BH had a significant effect on both the adhesive properties and the characteristics of the manufactured plywood. The application of non-modified husks led to a reduction in viscosity and an extension of the gelation time, and the produced plywood boards were characterized by reduced bonding quality and increased delamination. Modification of the husk surface by acetylation and silanization with 3-aminopropyltriethoxysilane contributed to the noticeable improvement in the resin properties. On the other hand, the improvement in plywood properties, consisting of the increase in bonding quality and reduced delamination, was observed only in the case of the silanized husk. Furthermore, the use of non-modified and acetylated husk did not significantly influence the formaldehyde emission. The reduction in the investigated emission of formaldehyde was observed only in the case of variants containing 15 and 20% of silanized buckwheat husk. [ABSTRACT FROM AUTHOR]

An investigation was made of wood of the species oak (Quercus petraea), beech (Fagus sylvatica L.), maple (Acer pseudoplatanus) and ash (Fraxinus excelsior) pre-treated using radio-frequency (RF) plasma in air at reduced pressure. Physical and chemical changes for all of the wood species were determined using measurements of water contact angles and FTIR-ATR spectroscopy. The results confirmed an increase in the wood’s hydrophilicity/polarity in all cases, caused by an increase in –OH group concentration due to irradiation by RF plasma. The content of oxygen-containing functional groups after treatment by RF plasma significantly increased, and the water contact angles were diminished. FTIR-ATR spectroscopy confirmed that RF plasma modification of the surfaces of all investigated wood samples led to certain changes, which were also dependent on the time of plasma exposure. [ABSTRACT FROM AUTHOR]

A barrier plasma, created at atmospheric pressure, was used to improve the surface and adhesive properties of polyester (PES) film with respect to wood using polyurethane adhesives. The modification of PES film surfaces using barrier discharge plasma is attractive for various applications. Plasma pre-treatment initiates and participates in grafting, polymerization, or cross-linking reactions on the PES surface. This method of surface modification is clean, dry, ecological, and very efficient. The enhancement of the wettability of the polyester film was necessary for promoting higher adhesion to wood with water-based adhesives. The treatment of polyester films by barrier plasma led to a considerable increase in the surface free energy of the film and subsequently an increase in the peel strength of the adhesive joint of PES film-oak wood with polyurethane adhesive. [ABSTRACT FROM AUTHOR]

The aim of this study was to improve the properties of lightweight particleboards by their veneering. The industrially produced wood particles, rotary-cut birch veneer, expanded polystyrene (EPS) granules and urea-formaldehyde (UF) resin were used to manufacture non-veneered and veneered boards in laboratory conditions. The boards were manufactured with different densities of 350, 450 and 550 kg/m3 and with various levels of EPS content 4, 7 and 10%. Boards without EPS granules as the reference were also manufactured. Bending strength (MOR), modulus of elasticity in bending (MOE), internal bond (IB) strength, thickness swelling (TS) and water absorption (WA) of lightweight particleboards were determined. This study confirmed that veneering of lightweight particleboards by birch veneer improved mechanical properties significantly. The MOR and MOE of veneered boards throughout the whole density range of 350–550 kg/m3 meet the requirements of the CEN/TS 16368 for lightweight particleboards types LP1 and LP2. The IB strength of veneered boards only with density of 550 kg/m3 meets the requirements of CEN/TS 16368 (type LP1). The MOR, MOE and IB of non-veneered boards also meet the requirements of CEN/TS 16368 (type LP1) except boards with density of 350 kg/m3 for MOR and MOE, and except densities of 350 and 450 kg/m3 for IB. [ABSTRACT FROM AUTHOR]

This research optimizes the process of plywood production to determine its effectiveness in reducing energy and adhesive consumption for more efficient production with the required quality. The influence of selected parameters including veneer treatment (non-densified and densified), plywood structure, temperature, time and pressure of pressing, on the bonding quality and temperature evolution within the veneer stacks during hot pressing was investigated. Rotary-cut, non-densified and densified birch veneers and phenol formaldehyde (PF) adhesive were used to manufacture plywood samples. The effect of pressure and time of pressing on bonding quality of the plywood was determined. Bonding quality was evaluated by determining the shear strength of the plywood samples. The temperature evolution inside the veneer stacks was measured for birch veneers for different pressing temperatures and pressures for different numbers of veneer layers. The heating rate of the veneer stacks increased as the pressing temperature increased and decreased markedly with an increasing number of veneer layers. At a high pressing pressure, the heating rate of the densified veneer stacks was faster than that of non-densified veneers at the same pressure. The use of densified veneers for the production of plywood can lead to a shorter pressing time (17–50% reduction), lower glue consumption (33.3% reduction) and a lower pressing pressure (22.2% reduction) without negatively impacting the bonding strength of the plywood. [ABSTRACT FROM AUTHOR]

In this study, the effect of the veneer-drying process at elevated temperatures on selected properties and formaldehyde emission of plywood panels was determined. We assume that during the veneer drying at high temperatures, more formaldehyde is released from it, and therefore, a lower formaldehyde emission can be expected from the finished plywood. Prior to bonding, birch veneers were dried at 160 °C (control) and 185 °C in an industrial veneer steam dryer (SD) and at 180 °C, 240 °C and 280 °C in an industrial veneer gas dryer (GD). Two types of adhesives were used: urea–formaldehyde (UF) and phenol–formaldehyde (PF) resins. Bonding quality, bending strength and modulus of elasticity in bending, water absorption and thickness swelling of plywood samples were determined. The formaldehyde emission level of samples was also measured. It was concluded from the study that the effects of veneer-drying temperatures on the bonding strength and physical and mechanical properties of plywood panels were significant. Veneer-drying temperatures of 185 °C/SD, 180 °C/GD and 240 °C/GD negatively affected the bending strength and the modulus of elasticity along and across the fibres for both UF and PF plywood samples. Bonding strength mean values obtained from all test panels were above the required value (1.0 MPa) indicated in EN 314-2 standard. The lowest formaldehyde emissions for the UF and PF plywood samples were observed in the samples from veneer dried in a steam dryer at 185 °C/SD. [ABSTRACT FROM AUTHOR]

Thermoplastic films exhibit good potential to be used as adhesives for the production of veneer-based composites. This work presents the first effort to develop and evaluate composites based on alder veneers and high-density polyethylene (HDPE) film. The effects of hot-pressing temperature (140, 160, and 180 °C), hot-pressing pressure (0.8, 1.2, and 1.6 MPa), hot-pressing time (1, 2, 3, and 5 min), and type of adhesives on the physical and mechanical properties of alder plywood panels were investigated. The effects of these variables on the core-layer temperature during the hot pressing of multiplywood panels using various adhesives were also studied. Three types of adhesives were used: urea–formaldehyde (UF), phenol–formaldehyde (PF), and HDPE film. UF and PF adhesives were used for the comparison. The findings of this work indicate that formaldehyde-free HDPE film adhesive gave values of mechanical properties of alder plywood panels that are comparable to those obtained with traditional UF and PF adhesives, even though the adhesive dosage and pressing pressure were lower than when UF and PF adhesives were used. The obtained bonding strength values of HDPE-bonded alder plywood panels ranged from 0.74 to 2.38 MPa and met the European Standard EN 314-2 for Class 1 plywood. The optimum conditions for the bonding of HDPE plywood were 160 °C, 0.8 MPa, and 3 min. [ABSTRACT FROM AUTHOR]

The oil palm plantations in Indonesia have prompted the need for technology to utilize nonproductive oil palm trees (Elaeis guineensis Jacq.). This study was aimed to collect information on the quality of oil palm trunk veneer modified using SRF impregnation from oil palm bark extract. The impregnant was synthesized by copolymerizing resorcinol (R) and formaldehyde (F) on palm bark extract (S). Fourier Transform Infrared (FTIR), PyrolysisGas Chromatography-Mass Spectroscopy (Py-GCMS), X-Ray Diffraction (XRD), and Differential Scanning Calorimetry (DSC) were used to characterize the oil palm resorcinol formaldehyde (SRF) resin. The SRF-impregnant material was used to improve the oil palm veneer's density, thickness, swelling, stiffness, and strength. The results of the DSC analysis showed that the SRF resin was thermoset. The SRF-impregnated palm veneer could increase the veneer density by 20%, lower thickness swelling below 25%, and increase the modulus of rupture (MOR) by over 10% and modulus of elasticity (MOE) by 50%. [ABSTRACT FROM AUTHOR]

Considering the significant production volume of wood composite materials, the search for ecological solutions to reduce formaldehyde emissions during their pressing and further operation is urgent. The effect of nanoparticles of zinc, aluminium, and iron metals on formaldehyde emission from particleboard samples during their manufacture and subsequent exposure for three weeks is examined in the paper. Nanoparticles of metals were produced by the electro-spark method. In order to determine the priority metal, the method of analysis of hierarchies and search experiments was used. Samples of particleboard were made with the addition of a modified glue based on UF resin. Nanoparticles of the metals Zn, Al, and Fe were used in concentrations of 2% and 8%, respectively, to modify the adhesive resin. Measurements of the level of free formaldehyde were carried out on the third and seventeenth days after the pressing of particleboard samples. The results of experimental studies confirmed the theoretical calculation of priority based on the selected assessment criteria. The best results were observed when zinc was used as a filler at a concentration of 8%. [ABSTRACT FROM AUTHOR]

A comparative analysis of the quality properties of coating materials based on linseed oil and alkyd film formers is provided in the paper. The advantages and disadvantages of linseed oil-based and alkyd-based coating materials are explored. Protective materials such as alkyd coating material for wood and drying linseed oil were applied on the compared pine-wood samples. The authors determined the drying time of linseed oil and alkyd coating materials on pine wood, the thickness of the dry film, heat resistance, lightfastness, as well as water resistance of protective and decorative coatings. Linseed oil-based coating materials form thin-layer coatings on the surface of wood, unlike coatings based on alkyd materials. Alkyd coating materials transitioned into a solid state faster than the linseed oil-based ones. Coatings based on linseed oil have a higher moisture resistance. Higher indicators of heat resistance were observed in coatings based on linseed oil materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study we assessed the efficacy of manufacturing lightweight particleboards using sunflower (Helianthus annuus L.) stalk particles. Three-layer lightweight particleboards with target densities of 350, 450 and 550 kg/m3 were produced with different proportions of wood-to-sunflower stalk particles (100:0%, 75:25%, 50:50%, 25:75%, 0:100%) in the core layer. The outer layers consisted only of wood particles. The boards made entirely with wood particles in the outer and core layers were reference boards. Conventional urea-formaldehyde (UF) resin was used to bond the particles. It was found that the replacement of wood particles in the core layer with sunflower stalk particles led to an improvement in the physical and mechanical properties of lightweight UF-bonded particleboards. Three-layer boards with the optimum combination of 100% wood particles in the outer layers and 100% sunflower stalk particles in the core layer had slightly higher bending strength (MOR) and modulus of elasticity (MOE) than boards made entirely from 100% wood particles, but much greater internal bonding strength (IB), lower water absorption (WA) and less thickness swelling (TS) at the same board density. The MOR, MOE and IB values for 550 kg/m3 boards containing 100% sunflower particles in the core layer were higher than the reference boards by 16.3%, 16.6% and 62.7%, respectively. The MOR, MOE and IB of lightweight particleboards with densities of 450 and 550 kg/m3 made with 100% sunflower particles in the core layer fully complied with the CEN/TS 16368 standard for both types of board, LP1 and LP2. Substitution of wood particles with sunflower stalk particles did not cause negative changes in the formaldehyde content of the boards. • The possibility of making lightweight PBs from SSP was confirmed. • Including SSP in the core layer improves the IB strength of boards. • Including SSP in the core layer decreases the WA and TS of boards. • Lightweight PBs from SSP meet the requirements of CEN/TS 16368. • Using of SSP in the manufacture of PBs saves wood raw materials. [ABSTRACT FROM AUTHOR]

Low-temperature plasma was used to improve the surface and adhesive properties of wood. The pre-treatment of wood surfaces using radio-frequency (RF) discharge plasma is attractive for various wood applications, mainly because of the high efficiency and low production cost of the process. In addition, a significant increase in the polar component of the wood surface energy, which is associated with the presence of acid–base interactions (electron donor–acceptor bonds), after modification by RF discharge plasma was identified. The treatment of wood by RF plasma exhibited an aging effect, with the modified surface never recovering its initial hydrophobic state. Indeed, the enhancement of the wettability of wood is necessary for promoting better adhesion with water-based adhesives and coatings, which is currently the subject of ongoing study. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) is one of the most widely used polymers in many industrial applications. Biomedical uses seem to be attractive, with increasing interest. However, PE it prone to infections and its additional surface treatment is indispensable. An increase in resistance to infections can be achieved by treating PE surfaces with substances containing antibacterial groups such as triclosan (5-Chloro-2-(2,4-dichlorophenoxy)phenol) and chlorhexidine (1,1'-Hexamethylenebis[5-(4-chlorophenyl)biguanide]). This work has examined the impact of selected antibacterial substances immobilized on low-density polyethylene (LDPE) via polyacrylic acid (PAA) grafted on LDPE by low-temperature barrier discharge plasma. This LDPE surface treatment led to inhibition of Escherichia coli and Staphylococcus aureus adhesion; the first causes intestinal disease, peritonitis, mastitis, pneumonia, septicemia, the latter is the reason for wound and urinary tract infections. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the feasibility of using magnesium and sodium lignosulfonates (LS) in the production of particleboards, used pure and in mixtures with urea-formaldehyde (UF) resin. Polymeric 4,4′-diphenylmethane diisocyanate (pMDI) was used as a crosslinker. In order to evaluate the effect of gradual replacement of UF by magnesium lignosulfonate (MgLS) or sodium lignosulfonate (NaLS) on the physical and mechanical properties, boards were manufactured in the laboratory with LS content varying from 0% to 100%. The effect of LS on the pH of lignosulfonate-urea-formaldehyde (LS-UF) adhesive compositions was also investigated. It was found that LS can be effectively used to adjust the pH of uncured and cured LS-UF formulations. Particleboards bonded with LS-UF adhesive formulations, comprising up to 30% LS, exhibited similar properties when compared to boards bonded with UF adhesive. The replacement of UF by both LS types substantially deteriorated the water absorption and thickness swelling of boards. In general, NaLS-UF-bonded boards had a lower formaldehyde content (FC) than MgLS-UF and UF-bonded boards as control. It was observed that in the process of manufacturing boards using LS adhesives, increasing the proportion of pMDI in the adhesive composition can significantly improve the mechanical properties of the boards. Overall, the boards fabricated using pure UF adhesives exhibited much better mechanical properties than boards bonded with LS adhesives. Markedly, the boards based on LS adhesives were characterised by a much lower FC than the UF-bonded boards. In the LS-bonded boards, the FC is lower by 91.1% and 56.9%, respectively, compared to the UF-bonded boards. The boards bonded with LS and pMDI had a close-to-zero FC and reached the super E0 emission class (≤1.5 mg/100 g) that allows for defining the laboratory-manufactured particleboards as eco-friendly composites. [ABSTRACT FROM AUTHOR]