Adhesive Spread Research Articles

Properties of laminated board from Belangke bamboo (Gigantochloa pruriens) modified with citric acid, boric acid, and polystyrene

ABSTRACT The development of bamboo as a raw material for construction materials has drawbacks, including low physical properties. Therefore, this work aimed to determine the physical and mechanical properties of laminated boards modified with citric acid, boric acid, and polystyrene. In addition, the study analysed the optimum immersion time and the phenomenon of the modifications provided. Two-step conditions were designed for the immersion of bamboo lamina. The first steps were prepared at different variation times (6, 12, and 24 h). The effect of variation time was evaluated to obtain the optimum duration treatment of bamboo lamina. Then, another step of bamboo lamina was immersion for different solutions (citric acid, boric acid, and polystyrene) at an immersion time of 6 h. The bamboo lamina was assembled into laminated boards (3 layers) measuring 30 cm × 15 cm × 1.5 cm (length × width × thickness) using isocyanate adhesive with adhesive spread level of 280 g/m2 using the double adhesive spread technique. The physical and mechanical properties of the laminated board were tested according to the JAS 234:2003 standard. The laminated board modified with polystyrene has higher density, lower delamination, higher shear strength, and higher modulus of elasticity (MOE) and modulus of rupture (MOR) than that modified with citric acid and boric acid. In addition, the bamboo laminated with 6 h and polystyrene immersion has density, moisture content, delamination, MOE, and MOR that meet the JAS 234:2003 standard. These phenomena are due to changes in the functional group and crystallinity of bamboo laminated after immersion.

Optimizacija parametara proizvodnje ugušćene lamelirane furnirske građe proizvedene upotrebom urea-formaldehidne smole

This research aims to optimize densified laminated veneer lumber production parameters of compression ratio, press temperature, press time, and adhesive spread rate to maximize their mechanical properties. In the manufacturing process of densified laminated veneer lumber, I-77/51 American poplar clone (Populus deltoides) veneers and urea formaldehyde adhesive are used. The results showed that the compression rate and press time had the most significant impact on the mechanical properties of densified laminated veneer lumber. The optimal production conditions were determined as follows: 38 % compression, press temperature of 170 °C, press time of (10±3) minutes, and spread rate of 150 g/m2. Modulus of rupture, modulus of elasticity, tensile shear strength, and tensile strength perpendicular to panels surface of densified laminated veneer lumbers produced under these conditions increased by 49 %, 8 %, 71 %, and 23 %, respectively, compared to the control group of laminated veneer lumber. So, it can be said that the production parameters of densified laminated veneer lumbers can be optimized safely and effectively using Taguchi method-based grey relational analysis.

Manufacturing Study on Different Glue Spread and Press Pressure for Glued Laminated Timber Made from Laran

Amidst challenges such as dwindling timber log supply from natural forests, concerns about timber quality, and rising timber costs, the timber industry has increasingly turned to engineered lumber solutions, including glued laminated timber (glulam) crafted from fast-growing species. However, the performance of glulam derived from plantation trees, notably swift-growing varieties like Laran, remains an area warranting exploration. This study addresses critical aspects of glulam production, encompassing adhesive selection, spread rate, and press pressure, which collectively influence material performance. The objectives of this research encompass an assessment of the bonding integrity of glulam originating from Laran plantation species and an evaluation of the optimal adhesive spread rate and press pressure for Laran-derived glulam. Various adhesive spread rates (200 g/m2, 250 g/m2, 350 g/m2 and 400 g/m2) and press pressures (0.7, 1.0 and 1.4 MPa), utilizing Phenol-Resorcinol Formaldehyde (PRF) adhesives, were systematically investigated in alignment with the guidelines stipulated in MS 758: 2020. Bonding integrity was evaluated via block shear and cyclic delamination tests. The study reveals that these parameters indeed exert a tangible influence on the bonding efficacy of PRF adhesive with Laran species. Remarkably, an optimal adhesive spread rate of 399.78 g/m2 and press pressure of 1.18 MPa emerged as pivotal thresholds for superior bonding outcomes. Notably, the significance of adeptly designed glulam beams within wooden structural frameworks is underscored, particularly in light of the multifaceted imperatives of sustainability, economics, and environmental conscientiousness.

Properties of engineered wood flooring with cold-pressing and emulsion polymer isocyanate adhesive

For the sake of improving the product quality and economy, a series of cold-pressing experiments were carried out to investigate the material properties of engineered wood flooring with emulsion polymer isocyanate adhesive. Effect of pressing time, pressure, and adhesive spreading rate on modulus of elasticity (MOE) and modulus of rupture (MOR) was analyzed based on orthogonal experimental design. According to the results, both the MOE and MOR were positively correlated with pressing pressure and adhesive spreading rate. The MOE first increased and then decreased with the increase of pressing time, and MOR showed an increasing trend with the pressing time. Meanwhile, pressing time had the greatest effect on the MOE, followed by adhesive spreading rate, and pressing pressure. However, adhesive spreading rate had the greatest influence on the MOE, followed by pressing time and pressure. Furthermore, pressing time had a significant contribution to both MOE and MOR, and adhesive spread rate had a significant effect on only the MOR. Finally, the optimal cold-pressing condition was determined as 18 s pressing time, 1.25 MPa pressure, and 200 g/m3 adhesive spreading rate, and it is proposed for application in the industrial cold pressing of engineered wood flooring for the highest MOE, MOR, and production benefit.

Performance of Glued Laminated Timber (Glulam) Made from Kelempayan Wood with Different Lamina Assembly Patterns and Adhesive Spread Rates

This study investigates the impact of adhesive spread rates and lamina assembly patterns on the physical and mechanical properties of glue laminated lumber (glulam) manufactured from Kelempayan wood (Neolamarckia cadamba (Roxb.) Bosser). For this purpose, lab-scale 3-ply homogenous glulams were manufactured using low-MOE, average-MOE, and high-MOE laminas, and 3-ply mixed glulams of low-high-low-MOE and high-low-high-MOE lamina, with an adhesive spread rate of 100 g/m2 applied on both sides of the lamina. A 3-ply homogenous glulam was also manufactured using the average-MOE lamina with an adhesive spread rate of 200 g/m2. The physical and mechanical properties of the glulam, including moisture content, density, modulus of rupture (MOR), and modulus of elasticity (MOE), were examined and compared to the Japanese Industrial Standards (JAS) for glulam. The results found that the adhesive spread rates did not have a significant effect on the physical and mechanical properties of the glulam. However, the lamina assembly patterns had a significant impact on the mechanical properties of the glulam. The highest MOR and MOE were observed in the homogenous glulam manufactured from the high-MOE laminas, followed by the mixed glulam manufactured from the high-low-high-MOE laminas. These assembly patterns meet the MOR and MOE requirements specified in the 3-ply homogeneous structural grade glulam standard, indicating that Kelempayan wood can be a feasible option for glulam production.

Performance of glued laminated timber (glulam) made from Rubberwood with different lamina assembly patterns and adhesive spreads rates

Glued laminated timber (glulam) is a great building material with strong mechanical properties that comprises laminated layers of wood (lamina) glued together with long-lasting structural adhesives. As the supply of large dimensional lumber for construction projects has been in shortage, glulam is the ideal material to replace the lumber because it can be made in various sizes and shapes, including unique arches using relatively small dimensional lumber. This research aims to investigate the effects of different lamina assembly patterns and adhesive spread rates on the physical and mechanical properties of rubberwood glulam. For this purpose, the lab scale of the 3-ply glulam was made from homogenous grades lamina of low-MOE, average-MOE, and high-MOE. In addition, the lab scale of the 3-ply glulam was also produced from mixed grades lamina of low-high-low-MOE and high-low-high-MOE. The glulam was tested to evaluate the physical and mechanical properties based on the Japanese Industrial Standards for glulam (JAS 234-2003). The results show that the lamina assembly patterns significantly affect the mechanical properties of the glulam. Accordingly, the glulam made from a high-MOE lamina at its compression and tension surfaces has the best mechanical properties compared to that made from the other assembly patterns. In addition, although the difference was insignificant, the results showed that adhesive spread rate has positively affected the mechanical properties of the glulam. The results showed that Rubberwood has the potential to be used as raw material for glulam production.

Analysis of the adhesive spread and the thickness of the adhesive bonded joint depending on the compressive force applied to bonded materials with different surface structure

The thickness of the adhesive layer in a bonded joint is one of the important factors determining its strength and its recommended value varies depending on the type of the adhesive used and the type of load on the joint. Specimens for testing adhesively bonded joints with a specified thickness of the layer are usually produced under laboratory conditions using spacers of a specified thickness, and the remaining excess adhesive is removed from the specimen. In industrial conditions, this method of obtaining an appropriate thickness of the adhesive layer is not always possible and desirable. The method of adhesive spreading between the joined plates under the influence of pressure without spacers was analysed. For this purpose, 3 pairs of aluminium plates were used, differing in surface texture and roughness for the Ra parameter at 0,25 μm, above 3 μm, and above 5 μm. 0.5 ml of Bonapur RZ45 polyurethane adhesive was compressed between the plate pairs without additional force (except for the own weight of the plates) and with load of 50 N, 100 N, 250 N, and 500 N. The surface where the adhesive would be distributed was checked to estimate the resulting thickness of its layer. The size of the layer ranged from 0.09 (for the force 500 N) to 0.53 mm (without additional force, only plate). The values obtained of the layer thickness in the case of using additional force are lower than recommended in the literature (0.5–2 mm) for polyurethane adhesives. The measurements showed that the roughness of the surface does not significantly affect the differences in the resulting thickness of the adhesive layer, whereas the visible surface machining footprint causes changes in the way the adhesive spreads and impacts the shape of the adhesive on the plate surface.

Adhesion performance of melamine-urea–formaldehyde joints of copper azole-treated Eucalyptus grandis at varied bonding process conditions

The effect of copper azole impregnation, wood density, adhesive spread rate, mechanical pre-treatment, open and close assembly times, bonding pressure, and press duration on melamine-urea–formaldehyde-bond performance of Eucalyptus grandis joints was investigated. The results obtained showed that the shear strength was mainly affected by copper azole concentration and bonding pressure while wood failure and delamination were mainly affected by wood density, copper azole concentration, and mechanical pre-treatment. With the adaptation of bonding parameters, results suggest that satisfactory improvement of melamine-urea–formaldehyde-bond performance in copper azole-treated E. grandis laminates is feasible. This will make the production of treated hardwood laminated composites for structural applications in tropical and sub-tropical regions attainable.

Investigation of the adhesion performance of some fast-growing wood species based on their wettability

Abstract The objective of this study was to investigate the adhesion performance of eight fast-growing wood species, namely, Enterolobium cyclocarpum, Paraserianthes falcataria, Shorea sp., Toona sinensis, Gmelina arborea, Pinus merkusii, Acacia mangium, and Acacia hybrid obtained from the tropical region. The wettability test was conducted by contact angle measurement, while the adhesion performance was expressed by strength retention (SR) and wood failure (WF) percentages through block shear tested under the Japanese Agricultural Standard (JAS). Results showed that smaller contact angle for P. falcataria followed by E. cyclocarpum, P. merkusii, T. sinensis, and Shorea indicated that the surfaces were easier to be glued than that of G. arborea, A. mangium, and A. hybrid. It is indicated that high wettability of P. falcataria, E. cyclocarpum, P. merkusii, T. sinensis, and Shorea resulted in the better adhesive spread and more intimate contact between the wood surface and the adhesive as shown by their high SR with high WF percentages.

Chitosan-Based Adhesive: Optimization of Tensile Shear Strength in Dry and Wet Conditions

Commercial adhesives present a high bond strength and water resistance, but they are considered non-healthier products. Chitosan can be considered as an interesting biosourced and biodegradable alternative, despite its low water resistance. Here, its wood bonding implementation and its tensile shear strength in dry and wet conditions were investigated depending on its structural characteristics. Firstly, the spread rate, open assembly time, drying pressure, drying temperature, and drying time have been determined for two chitosans of European pine double lap specimens. An adhesive solution spread rate of 1000 g·m−2, an open assembly time of 10 min, and a pressure temperature of 55 °C for 105 min led to a bond strength of 2.82 MPa. Secondly, a comparison between a high molecular weight/low deacetylation degree chitosan and a lower molecular weight/higher deacetylation degree chitosan was conducted. Tests were conducted with beech simple lap specimens in accordance with the implementation conditions and the conditioning treatments in wet and dry environments required for thermoplastic wood adhesive standards used in non-structural applications (EN 204 and EN 205). The results clearly revealed the dependence of adhesive properties and water resistance on the structural features of chitosans (molecular weight and deacetylation degree), explaining the heterogeneity of results published notably in this field.

Experimental study on bending and shear behaviours of composite timber sandwich panels

Composite sandwich panels were manufactured by gluing plywood skins to either bamboo rings to produce Bamboo Core Sandwich (BCS) panels or to peeler core rings to produce Peeler Core Sandwich (PCS) panels. Single and double core layer panels were made. The optimum adhesive spread rate was identified through conducting shear bond tests. The manufactured panels were physically tested in standard bending (using four-point) and shear (using three-point) tests. Results were compared to the test results of conventional Cross-laminated Timber (CLT) panels with almost similar depth. Under bending action, both the BCS and PCS panels showed tensile failure in the plywood, while the plywood in compression exceeded its plastic limit at the ultimate load. In shear, BCS panels failed due to the loss of shear interface contact between bamboo core rings and the plywood skins, whereas PCS panels showed local indentation/bond failure between the peeler core rings and the plywood skins. No significant improvements were observed in the double-layer panels compared to single-layer panels in bending. However, in shear, double-layer panels showed more consistent capacities. One PCS panel with thicker plywood skins and less peeler core rings (PCS-TH) was manufactured, and was shown to achieve 0.77 times the bending stiffness-to-weight ratio of the commercial CLT panel. Reduced weight, lower material costs, ease of manufacturing and usage of sustainable/waste products, make the proposed sandwich panels a potential alternative for CLT in terms of structural performance. Moreover, the proposed peeler core sandwich panels displayed better ductile performances in bending and shear compared to CLT suggesting it could be a preferred product choice in some building applications.

Preparation and characterization of a bio-based polymeric wood adhesive derived from linseed oil

Increasing concerns over environmental health and safety, as well as diminishing fossil fuel reserves, motivate investigation into bio-based alternatives to petrochemically-derived adhesives. Adhesives derived from plant oils show promise as sustainable alternatives due to their abundance and low cost. Such adhesives are especially important in the growing domain of engineered lumber in which the material properties of low-value timber are enhanced using glued layers and joints. Linseed oil, which is derived from flax seeds, is a relatively unexplored feedstock for the preparation of eco-friendly wood adhesives. Herein, we report the preparation of a linseed oil-based adhesive and assess its strength on Liriodendron tulipifera (yellow poplar), Fraxinus americana (white ash) and Pseudotsuga menziesii (Douglas-fir). The results of a systematic study evaluating the influence of crosslinker choice, open-time, press time and adhesive spread rate on the shear strength of the adhesive-wood assembly are reported, as are results from water-soaking-and-drying tests that indicate excellent resistance of the linseed oil adhesive to water. Ultimately, these results show promise for use of the adhesive in timber applications.

Bonding strength of plywood bonded using phenol formaldehyde mixed with wood bark powder nanofiller

This paper investigates the wettability of selected wood species from Indonesian community forests, namely (Indonesian name–Latin name) surian (Toona sinensis), jabon (Anthocephalus cadamba), gmelina (Gmelina arborea.), Manglid (Manglietia glauca), rubber wood (Hevea brasiliensis), and sengon (Paraserianthes falcataria). The study measures the contact angle and evaluates the suitability of these wood species for plywood production. Logs from a community forest were processed to convert into thin slices of veneer using the rotary cutting method at a plywood plant. Subsequently, the study analyzed the wetting behavior of the veneer samples resulting from a rotary process on tangential surfaces without smoothing treatment with distilled water. The veneer was then made into plywood using an adhesive nanofiller of phenol formaldehyde mixed with wood bark powder. Ball milling produced nanofillers from the bark of jabon, gmelina, and surian with nanoscale particle diameter size (10–1000 nm). The bonding strength of the plywood was evaluated under cyclic and dry test conditions according to Japanese Standards. The study shows that P. falcataria, H. brasiliensis, and A. cadamba have a smaller contact angle than T. sinensis, G. arborea, and M. glauca. Thus, the higher wettability of P. falcataria, H. brasiliensis, and A. cadamba results in a better adhesive spread and more intimate contact between the wood surface and the adhesive. However, the study found higher bonding strength values for H. brasiliensis and T. sinensis plywood using jabon nanofiller, followed by T. sinensis plywood using surian nanofiller and H. brasiliensis plywood using gmelina nanofiller.

The flexural properties of medium density fibreboard overlaid with veneer from three species of wood

Aesthetic and strength are not easy to be combined in one wood composite product. This research aimed at combining both utilizing MDF overlaid with avocado, mahogany and pine veneer. Seven types of MDF composite plywood (comply) were designed using two adhesive types of Epoxy and Isocyanat. The adhesive spread weight was 250 g m-2. Cold compression was conducted within 3 hours with the pressure of 15 kg cm-2. The research results showed that flexural modulus (MOE) and flexural strength (MOR) of PMI comply (pine veneer, isocyanat adhesive) increased respectively by 129.5% and 75.9% when compared to MDF. This research recommends that MDF comply may be utilized for the structural and non-structural purposes.

Bonding quality assessment of cross-layered Maritime pine elements glued with one-component polyurethane adhesive

Abstract This paper presents an experimental study about the bonding quality of Maritime pine (Pinus pinaster Ait.) cross-layered wood elements glued with one-component polyurethane adhesive. The experiments comprised shear and delamination tests according to standard EN 16351 focusing on the influence of the following parameters: bonding pressure, adhesive spread rate, pre-treatment with primer and layer thickness. The results obtained show that increasing bonding pressure increases significantly the wood failure percentage after delamination or shear tests, while the delamination and the shear strength are not significantly affected. Moreover, it was found that the use of primer enhances significantly the bonding quality; nevertheless, EN 16351 requirements are fulfilled even for the lower bonding pressure and adhesive spread rate recommended by the manufacturer of the adhesive used in the experiments. The layer thickness, for the tested range, had no influence on the delamination and shear results and limited one on the wood failure percentage after shear or delamination tests. No relevant influence was found for the adhesive spread rate. In the experiments the combination of gluing Maritime pine with Australian blackwood (Acacia melanoxylon R.Br.) was also investigated and, for this combination, the standard requirements were successfully fulfilled.

On the static strength of aluminium and carbon fibre aircraft lap joint repairs

The behaviour of various aircraft lap joint repair configurations is investigated experimentally and numerically under static loading. The lap joints consist of aluminium alloy (AA) 2024-T3 substrates repaired with twin single-sided AA 2024-T3 or Carbon Fibre Reinforced Epoxy (CFRE) doublers. Pure riveted, pure bonded and hybrid (riveted and bonded) joints of metal–metal and metal–composite configurations are investigated. From experimental results, joints with adhesive bond showed nearly 5 times higher average strength than pure riveted joints, while hybrid joints performed better than riveted and bonded joints because of higher stiffness. On the other hand, hybrid metal–metal joint has 70% higher average strength compared to hybrid metal–composite joint. Rivet-shear has caused failure of riveted joints, and adhesive failure is observed in pure bonded joints. Hybrid joints with metal doublers have failed initially due to adhesive failure and later rivet shear. Interestingly, net-section failure is observed in composite doublers with breakage of doublers due to the presence of holes in the doublers. Experimental results are complimented with numerical analysis using commercial finite element code ABAQUS. Load–displacement curves obtained from the numerical results are in good agreement with experiments with a marginal error of 2%. In addition to load–displacement curves, a detailed stress analysis is performed numerically on metal–metal and metal-composite joints under riveted, bonded and hybrid configurations to study stress distribution on substrate and doublers. Numerical analysis showed hybrid and bonded joints have lower stresses in substrate and doublers compared to the riveted joints. Bonded joints have smoother load transfer due to the adhesive spread over a larger area. And finally, Stress Intensity Factors (SIFs) are performed numerically for unreinforced and reinforced metal substrate with crack length of 1, 5 and 10 mm with metal and composite doublers under riveted and bonded configuration. For crack of 10 mm, 35% reduction in SIFs is observed for reinforced substrate with bonded metal or composite doublers compared to unreinforced cracked substrate.

Influence of processing parameters and wood properties on the edge gluing of green Eucalyptus grandis with a one-component PUR adhesive

The predominant plantation hardwood species in South Africa Eucalyptus grandis is, despite relatively good strength and stiffness properties, seldom used for lumber production due to low dimensional stability, splitting, and cracking of the wood. As critical defects often develop or aggravate during the drying process, the edge gluing of Eucalyptus grandis lumber in its wet state, before kiln-drying, was considered a potential inhibiting factor for this behaviour. The objective of this study was to determine how certain material and processing variables influence the bond quality of unseasoned, edge-glued, Eucalyptus grandis, using a moisture-curing one-component polyurethane adhesive. The study considered the effect of four parameters, namely wood density, moisture content, adhesive spread rate and pressure, on the shear strength of bondlines. Micro computed tomography scanning was used to observe adhesive penetration behaviour. Overall, the bonding quality was satisfactory proving the feasibility of edge gluing of this wood in the wet state. Multiple ANOVA showed that generally better results were obtained for samples with a higher moisture content of roughly 60% compared to specimens with lower moisture content around fibre saturation point. Results indicated that the lower spread rate tested (150 g m−2) should be preferred to the higher one (250 g m−2), since it will likely give more stable shear strength results and it would be preferable from an economic point of view. Increasing pressure did not increase the shear strength significantly.

Bonding performance and mechanism of thermal-hydro-mechanical modified veneer

In the present study, fast-grown western hemlock (Tsuga heterophylla) was subjected to a thermal-hydro-mechanical (THM) treatment. Bond-line shear strength and durability were evaluated, and three parameters (substrate density, adhesive type and amount of adhesive spread) were investigated. To understand how THM processing affects bond performance, surface roughness and cell morphology of wood, before and after THM treatment, were observed. Adhesive penetration depths and patterns in untreated wood and THM-treated wood were also examined. In addition, Fourier transform infrared (FTIR) spectroscopy analysis of bond-line and microscopic observation of interphase region were conducted. Results revealed that polymeric diphenylmethane diisocyanate (PMDI) and polyurethane (PUR) had better bonding performance than phenol formaldehyde resin (PF). THM treatment improved bond durability, and THM plywood met the adhesive bond requirements of exterior plywood. THM treatment reduced surface roughness and porosity of wood. Adhesive penetration patterns were different in untreated wood and THM-treated wood and were affected by amount and type of adhesive. Pathways for adhesive flow into western hemlock were primarily tracheid lumens, ray cell lumens and the interconnecting pits. PF is the only adhesive that showed no evidence of flow via ray tissues or cell wall penetration. Since bond-line shear strength largely depends upon the weakest link across the laminas, ultimate strength or percent wood failure does not always depend merely on adhesive penetration. In addition, FTIR analysis showed different chemical reactions and bonding mechanisms, which provides a possible explanation of THM-caused changes in bonding performance at the molecular level.

Зменшення вмісту формальдегіду у фанері, склеєній карбамідоформальдегідними клеями з використанням деревинного волокнистого шламу

Щоб зменшити вміст формальдегіду у фанері, карбамідоформальдегідні клеї наповнювали деревинним волокнистим шламом. Під час досліджень використано: сухий подрібнений деревинний волокнистий шлам з розміром частинок менше 0,2 мм і вологістю 10%; карбамідоформальдегідну смолу КФ-МТ; амоній хлорид; березовий лущений шпон товщиною 1,5 мм і вологістю 6%. За допомогою багатофакторного планування експерименту досліджено вплив параметрів режиму склеювання шпону (кількості волокнистого шламу в клеї, витрати клею, тривалості та температури пресування) на вміст формальдегіду у фанері та міцність фанери на зріз. Вміст формальдегіду у фанері визначено методом WKI; міцність фанери на зріз – згідно з ДСТУ EN 314-1:2003 і ДСТУ ЕN 314-2:2006 (клас з’єднання 1). На вміст формальдегіду у фанері найбільше впливають витрата клею, у разі зменшення якої від 130 до 100 г/м2 вміст формальдегіду зменшується на 30-42 %, та температура пресування, в разі підвищення якої від 100 до 150˚С вміст формальдегіду зменшується на 34-41 %. У разі додавання до клею до 4 мас. ч. волокнистого шламу вміст формальдегіду у фанері зменшується на 16-30 %. На міцність фанери на зріз впливають кількість волокнистого шламу, в разі збільшення якого міцність частково знижується на 11-12 %, залишаючись більшою у 2,3-2,5 рази, порівняно з вимогами чинного стандарту, та температура пресування, в разі підвищення якої міцність зростає на 14-17 %. Отримані адекватні та відтворювані регресійні залежності властивостей фанери від досліджуваних факторів дають змогу спрогнозувати вміст формальдегіду у фанері та міцність фанери на зріз від параметрів режиму склеювання шпону.

Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood

In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 °C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 min prior to adhesive being applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one-third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa, which was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from uncompressed veneer. The findings in this study indicated that compression of birch veneer could be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.