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Thermal modification of wood changes its chemical, physical, and structural properties, which may affect adhesive bondline quality and bonding performance. This research compared the effect of thermal modification on the adhesive bonding performance of poplar (Liriodendron tulipifera) wood. Samples were prepared from thermally modified and unmodified yellow poplar using one-component polyurethane (PUR) and polyvinyl acetate (PVA), as they are adhesives used in wood products. Microscopic properties of the bondlines were investigated to understand shear performance and durability. Adhesive line thickness, penetration, shear strength, and moisture durability were measured, and failure modes were recorded. Thermal modification negatively affected the wood and adhesive interaction by reducing penetration (31.2% in PUR and 29% in PVA), therefore creating a thicker adhesive line (70% in PUR and 2% in PVA) and consequently causing a significant reduction in the shear strength of both adhesive types (27% in PUR and 36% in PVA) compared with non-modified specimens. The PUR adhesive had higher shear strength than PVA by 2.7% in non-modified and 14% in thermally modified wood. [ABSTRACT FROM AUTHOR]

Laminated veneer lumber (LVL) and reinforced laminated veneer lumber (RLVL) with carbon fiber were produced from heat-treated Scotch pine (Pinus sylvestris L.) wood using phenol formaldehyde (PF), polyvinyl acetate (PVAc), and polyurethane (PU) resins. Wood veneers were subjected to heat treatments at 150 °C, 170 °C, or 190 °C for 2 h before lamination. The effects of the reinforcement, heat treatment temperatures, and resins on the properties of the LVL and RLVL were analyzed. Density, equilibrium moisture content (EMC), modulus of rupture (MOR), and modulus of elasticity (MOE) were evaluated. The results showed that MOR and MOE values of solid wood and LVL specimens decreased with increasing treatment temperature. However, reinforcement with carbon fiber increased both MOR and MOE. In addition, the density values of the all RLVL specimens improved, and the EMC altered significantly for all test specimens. Compared to solid samples, the highest MOR values increased by approximately 21% in PF-RLVL samples. Similarly, the highest MOE values increased by 31% in PF-RLVL samples. In conclusion, carbon fiber, one of the most used fabric types in composites, could be utilized in the manufacture of reinforced LVL with heat-treated veneers. [ABSTRACT FROM AUTHOR]

Certain bamboo species have mechanical properties that are compatible with construction material. Despite this, their low shear strength, the presence of nodes in their culms, and their circular geometry inhibit the expansion of the use of this material as construction material. One technique that can solve these problems is glued laminated bamboo (GLB). Based on such findings, this paper aims to evaluate the physical and mechanical properties of glued laminated bamboo of the Dendrocalamus giganteus species. Two glues were used: resorcinolformaldehyde (PRF) and polyvinyl acetate (PVAc). The following physical and mechanical characterization tests were performed on glued laminated bamboo: water absorption, density, compression parallel to fiber direction, tension parallel to fiber direction, shear parallel to the glue layer, shear parallel to fiber direction, and bending. The results, analyzed using statistical models, showed that the GLB has physical and mechanical properties comparable to those of hardwoods. [ABSTRACT FROM AUTHOR]

Most wood properties are affected by changes in moisture content below the wood fiber saturation point. In this study, the thickness swelling ratios of laminated veneer lumber (LVL) produced from Scotch pine (Pinus sylvestris L.) bonded by using polyvinyl acetate (PVAc), polymeric diphenyl methane diisocyanate (pMDI), and a mixture of them were evaluated. Thickness swelling of the samples was calculated after different waiting times under water. While the lowest thickness swelling ratio (1.65%) was determined from bonding with PVAc 92%- pMDI 8%, for 2 hours, the highest thickness swelling ratio (6.35%) was observed from bonding with PVAc 98%- pMDI 2% adhesive for 96 hours. As a result, adding pMDI to the PVAc adhesive reduced the rate of swelling of the test specimens. For this reason, the material can be used potentially in wet or humid places. [ABSTRACT FROM AUTHOR]

Next-generation laminated wood composites were produced using waste poplar (Populus deltoides) veneer and polyvinyl acetate adhesive. Four experimental groups and one control group were created. Ten-layer laminated wood veneer samples were reinforced with natural rubber (Group A), linoleum (Group B), felt (Group C), and elastomeric sponge (Group D); these materials were used in the fifth adhesive layer (middle layer). The sound absorption coefficients of the control and experimental groups were tested via the impedance tube method, according to ASTM standard E1050 (2006). Attention was paid to the acoustic behavior at low frequencies (63 Hz to 250 Hz), mid frequencies (250 Hz to 2000 Hz), and high frequencies (2000 Hz to 6300 Hz). It was determined that the sound absorption coefficient of the experimental groups considerably increased. It can be suggested that the experimental groups be used as sound absorbing acoustic panels and the control group as sound reflective acoustic panels. [ABSTRACT FROM AUTHOR]

Effects of the wood species, number of teeth, and adhesive type were studied relative to the moment capacities of box joints under tension and compression loadings, which is commonly used in case type solid wood furniture. For this purpose, L-type specimens were prepared from Scotch pine (Pinus sylvestris L.), poplar (Populus sp.), and fir (Abies sp.). Polyvinyl acetate (PVAc) and polyurethane (PU) adhesives were used in the preparation of joints. Tension and compression tests with 360 samples were performed under static loading. According to the results, the highest moment capacities were obtained for Scotch pine under tension, and poplar specimens under compression. With respect to the number of teeth, the highest moment capacities were obtained with 12-tooth joints under both tension and compression loadings. For adhesive types, the specimens glued with PVAc gave better results in both tension and compression. In manufacturing of solid wood based case-type furniture, the higher number of teeth resulted in a slightly better performance; however, the results with the 4-tooth structure was not too far from 8-tooth. Furthermore, it was concluded that Scotch pine as a substance and PVAc as adhesive could be recommended. [ABSTRACT FROM AUTHOR]

Reforestation wood is interesting for construction, due to its potential as material source for manufacturing. For this purpose, the Eucalyptus genus has resulted in a better characterization of the material properties. During the production process, wood is machined at some stage, which influences the wood gluing quality. This study considered the performance of Eucalyptus saligna wood joints bonded with four commercial polyvinyl-acetate-based resins with different physical characteristics and chemical compositions. The surfaces of samples were prepared and machined by an up-milling process, using a planer, with wood feed rates of 6 m/min, 11 m/min, 16 m/min, and 21 m/min, which had advances per tooth of 0.25 mm, 0.45 mm, 0.66 mm, and 0.87 mm, respectively. The samples were prepared for shear strength testing of the glue line. During the preparation, all pieces were randomly bonded with regards to the formation plans of wood growth rings. Shear strength values were statistically compared to analysis of variance and Tukey test. Only C4 adhesive reached good results at all feed rates as well as having the best shear strength compared to other resins. Commercial adhesives had distinct interactions on the adhesive-wood interface, which resulted in different adhesion strengths. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the performance of composite wood blocks (CWB) by testing internal bonding, nail extraction resistance, and water absorption. The CWB were glued with two wood adhesives, polyvinyl acetate (PVAc), and urea formaldehyde (UF), modified with 1% nanocrystalline cellulose (NCC). Three tropical species were employed: Vochysia ferruginea, Cordia alliodora, and Gmelina arborea. In addition, the original European pallet in the static flexure test was evaluated. The results showed that the internal bonding relative to solid wood blocks (SWB) increased with both adhesives. Meanwhile, the CWB of V. ferruginea with UF and C. alliodora with PVAc showed the greatest resistance to nail extraction, while in G. arborea, the NCC increased the resistance to nail extraction. The CWB with modified adhesives absorbed more moisture, particularly with PVAc, compared with the SWB. In static flexure tests of the pallets fabricated with CWB, the load at the limit of proportionality and the maximum load increased, while deflections were lower, compared with SWB. The results showed the potential of utilizing NCC in CWB fabricated with tropical species. [ABSTRACT FROM AUTHOR]

Finger joints enable the full utilization of wood. The finger joint technique is used to eliminate wood defects that would otherwise weaken the wood strength. This research project evaluated how the wood species, adhesive type, and number of teeth affect the elastic stiffness of finger joints. The adhesives used were polyurethane and polyvinyl acetate, and the wood species were beech (Fagus sylvatica L.) and spruce (Picea abies L.). This study also determined the elastic stiffness of finger joints with 2 teeth and 5 teeth. For this purpose, the samples were loaded via a bending moment reaction, with tensile or compression forces in the angular plane. The highest elastic stiffness was obtained from the beech wood samples with 5 teeth bonded with polyvinyl acetate adhesive under tensile stress. Therefore, it was concluded that the elastic stiffness increased when the number of teeth increased. However, further studies on the elastic stiffness of finger joints are necessary in relation to the finger teeth length and surface area of the glue between the finger joint connections. [ABSTRACT FROM AUTHOR]

Knowledge of the force required to overcome deformation at the proportionality limit, yield point, as well as knowledge of the effect of selected factors on the characteristics during bending stress, have scientific and practical significance. They are the basis for designing tools for bending and accurately determining the stresses to which products and their parts may be subjected during use. This study analyzed the effect of selected factors on the selected characteristics, including the forces at the proportionality limit (FE) and yield point (FP). The chosen factors of this study were the wood species (Fagus sylvatica L. and Populus tremula L.), non-wood component (carbon and fiberglass), non-wood component position in the composition matrix (up and down), material thickness (6 mm, 10 mm, and 18 mm), and adhesive used (polyvinyl acetate and polyurethane), as well as their combined interaction. The results contributed to the advancement of knowledge necessary for the study and development of new materials with specific properties for their intended use. The results could improve the innovative potential of wood processing companies and increase their performance and competitiveness in the market. [ABSTRACT FROM AUTHOR]

The ground layer of Chinese ancient lacquer furniture is located below the lacquer film. It is a crucial layer to reinforce the restoration of the furniture, since the ground layer can increase the reinforced strength. In this experiment, lacquer films with and without ground layers were selected as the key materials that were bonded onto wood blocks with various ground layers via adhesives including lacquer, bone glue, and polyvinyl acetate (PVAC). A scanning electron microscope (SEM) and mechanical test machine were used to observe the ground layers, the permeation of the adhesives, and reinforced strength of lacquer film. The experiment showed that the ground layer can affect the reinforced strength of lacquer film in the permeation and effective bonding of adhesives. Good permeation increases the strength of lacquer film because of the coarse ground layer. The effective bonding of adhesives includes the filmformation of lacquer, the gel prevention of bone glue, and the successful polymerization of PVAC, which also can increase the strength of the lacquer film. [ABSTRACT FROM AUTHOR]

The main objective of this research was to analyse the synergistic effects of impregnation agents that are most commonly used in plywood production on the strength of bonded joints. Two water-based impregnations (Teknol aqua 1410-01 and Cetol WV 885 BPD+) and one solvent-based impregnation (Gori 605) were used in this study. The tested adhesives were polyvinyl acetate (PVAC) ADHESIVE 3384 (1-component PVAC adhesive), EPI (emulsion polymer isocyanate) system 1920/1993, and polyurethane (PUR) 1968 (1-component PUR adhesive). Test specimens were made from European beech timber (Fagus sylvatica L.) for plywood production according to EN 205 (2017). Individual tests were conducted according to EN 204 (2001) for PVAC adhesives, and according to EN 12765 (2001) for PUR adhesives. Although the effect of impregnation on bond strength was demonstrated, it was different depending on the type of adhesive. A clear positive synergistic effect on the bond strength was shown for isocyanate-based adhesives in almost all of the tests. The synergistic effect of PVAC adhesive was very variable in each individual test and showed a negative influence of higher moisture content and dipropylene glycol content in solvent-based impregnation. [ABSTRACT FROM AUTHOR]

Withdrawal strengths of commercially available hardwood dowels were examined in this work. Multi-grooved dowels with a straight surface pattern and with pre-glued polyvinyl acetate (PVAc) were tested. Additionally, standard dowels with different single- and multi-grooved surface patterns were also tested, which were not pre-glued. Standard dowels were bonded with two types of PVAc and one type of polyurethane (PUR) adhesive. The influence of the type of dowel, the surface pattern, the dowel diameter, and the type of adhesive used on the dowel joint strength were investigated. Lower average strengths were observed for single-grooved dowels with a spiral pattern (4.9 MPa); failures generally occurred at the first or second thread of the spiral groove. For the pre-glued dowels, there were differences in the observed strengths, which depended upon how the PVAc adhesive was activated. Lower withdrawal strengths were noted for the pre-glued dowels when they were activated by dipping them in water (3.0 MPa) versus adding water directly to the pre-drilled holes (4.7 MPa to 5.4 MPa). [ABSTRACT FROM AUTHOR]

Nanocellulose is a competitive reinforcement material for use in biocomposite structures and fibrous products. In this study, adhesive mixtures of dicarboxylic acid cellulose nanofibrils (CNF) were dispersed into commercial polyvinyl acetate (PVAc) and starch adhesives, which were applied to Norway spruce (Picea abies) to assess their performance in wood joining. Single-lap joints were prepared and tested with PVAc mixtures with 0 to 0.64 wt% CNF and starch glue mixtures containing 0 to 1.07 wt% CNF. CNF suspensions having three concentrations (0.64, 0.96, and 1.28%) were compared. The results showed that the optimum amount of CNF, 0.48% suspensions, added to PVAc increased the average lap joint strength (EN 205:2003) by 74.5% when compared to control specimens with pure PVAc. Correspondingly, 0.96% CNF suspensions also enhanced the strength of starch adhesive by 34.5%. Lower and higher CNF concentrations showed clearly inferior performance. [ABSTRACT FROM AUTHOR]

The effects of tenon size were investigated relative to the front to back loading performance of Scots pine (Pinus sylvestris L.) chairs. Forty-five chair frames were constructed with mortise and tenon joints with 9 tenon sizes. Joints were assembled with a 65% solids polyvinyl acetate (PVAc) adhesive. The front to back loading performance of chairs was compared to the acceptable design load levels given in the American Library Association (ALA) specifications. Chair frames were structurally analyzed with the Finite Element Method (FEM) to obtain the moment acting on each joint under loading. The results indicated that a chair became stronger as either tenon width or length increased, but was most affected by its length. As a result of structural analyses, front leg to side rail and back leg to side rail joints carried approximately 73% of the total moment that was induced under the front to back loading. According to the comparison results with acceptable design loads, chairs constructed with 40 mm × 50 mm tenons could meet light service (domestic usage), while the chairs constructed with 50 mm × 50 mm tenons could meet medium service. The chairs constructed with other sizes could not meet any acceptable levels, and thus need reinforcement. [ABSTRACT FROM AUTHOR]

The withdrawal force capacities were compared for T-type furniture joints made from heat-treated Siberian pine (Pinus sibirica), iroko (Chlorophora excelsa), and common ash (Fraxinus excelsior), which are commonly used in the construction of outdoor furniture. A total of 120 specimens that consisted of 3 wood species, 2 treatment processes (untreated and heattreated), 2 adhesive types (polyurethane and polyvinyl acetate), and 2 joinery techniques (mortise and tenon, and dowel) were tested, with 5 replications for each condition. Half of the specimens were constructed from heat-treated wood materials, while the remaining half were prepared from untreated wood materials (control specimens). The joints constructed from common ash and iroko exhibited the highest withdrawal force capacity values. Overall, heat treatment reduced the withdrawal force capacity of joints by 25% compared with the joints constructed of control specimens. Mortise and tenon joints yielded 4 times higher performance than dowel joints. The polyurethane adhesive gave better results than the polyvinyl acetate adhesive. The best withdrawal force capacity values of heat-treated wood materials were obtained from the Iroko-polyurethanemortise and tenon joint combination. [ABSTRACT FROM AUTHOR]

This article examines the effect of selected factors (wood species, lamella combination, type of adhesive, number of loading cycles) on the impact bending strength (IBS) of laminated wood. The IBS was tested on specimens made from beech (Fagus sylvatica L.) and aspen lamellas (Populus tremula L.). The laminated wood was densified by 10% and 20% of the original thickness. For bonding the wood, polyvinyl acetate (PVA) adhesive was used, and the product was compared with laminated wood bonded with polyurethane adhesive (PUR). The wood species and lamella combination had significant effects on IBS. The highest values of IBS were found for beech wood lamellas. [ABSTRACT FROM AUTHOR]

The effects of process parameters (adhesive spreading rate, pressing time, and applied pressure) on the response parameter (shear strength) of engineered wood flooring bonded with polyurethane (PUR) were studied by response surface methodology. A mathematical model was established to provide a satisfying prediction for the experimental results observed. The model indicated a high degree of fitting. The results also showed that the major factors were adhesive spreading rate and pressing time. The optimized parameters for highest shear strength of engineered wood flooring were 98 g/m2 adhesive spreading rate with pressing time of 24 s and applied pressure of 1.2 MPa, respectively, within certain ranges. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effect of surface roughness on bonding strength in Oriental beech, cherry, Scots pine, and Taurus cedar woods. In conformance with this objective, after planing the wooden materials under different conditions, their surface roughness values were determined in accordance with various standards using scanning equipment. The bonding strength test specimens were prepared using polyvinyl acetate (PVAc) and polyurethane (PUR) adhesives after the wooden materials were separated into three groups of varying surface roughness values, after which bonding strength experiments were carried out. The data obtained from the experiments were evaluated statistically at a 95% level of confidence. According to the test results, the highest bonding strength was obtained in the Oriental beech (9.27 N/mm²), whereas the lowest bonding strength was obtained in the Scots pine (3.65 N/mm²). There was not a statistically significant difference between the bonding strength of the cherry and Oriental beech woods. The PVAc adhesive (7.61 N/mm²) produced more successful results than the PUR adhesive (5.63 N/mm²). Furthermore, it was found that in the specimens with low surface roughness values for each wood type and used adhesives had high bonding strengths. [ABSTRACT FROM AUTHOR]

Joints are one of the most important issues in the design of furniture structures. Joints in furniture structures made from wood and wood materials represent a critical area because furniture most often breaks at the joints of structural elements. This article discusses the analysis of the effect of selected factors: type of loading (compressive, tensile), wood species (Fagus sylvatica L., Picea abies L.), thickness of joint (one-third and half the thickness of the tenon), type of glue (polyvinyl acetate and polyurethane), and the annual ring deflection, on the elastic stiffness of joints. These results indicated significant effects for the wood species, thickness of joint, and type of glue used. The annual ring deflection was on the borderline of statistical significance, while its effect was more significant than the effect of the basic material characteristic, i.e., the wood density. The type of loading was not statistically significant. [ABSTRACT FROM AUTHOR]

This article deals with the effects of various parameters on the shear bond strength (SBS) of glued wood. A four-factor analysis showed that the combination of only non-densified wood pieces achieves higher shear bond strength values than densified ones. In this case, only the piece combination was a significant factor. The other factors (glue type, wood species, and number of loading cycles) had no significant effect. Although the differences were not large, a higher SBS was achieved in beech wood glued with polyvinyl acetate (PVAc) glue. Glued wood consisting of the combination of densified and non-densified pieces had slightly lower SBS values. In this case, all the factors were statistically significant. Beech wood had a more significant impact on the SBS than aspen wood. The effect of the type of glue showed an opposite trend than that in the previous variant, i.e., a higher SBS was achieved with polyurethane (PUR) glue. Wood subjected to cyclic loading had slightly higher SBS values than non-cyclically loaded wood. The degree of densification had no significant effect. Glued wood composed entirely of densified pieces showed greater SBS variation between versions. [ABSTRACT FROM AUTHOR]

Specimens taken from Pinus nigra Arnold were subject to surfacing techniques by being cut with a circular saw, planed with a thickness machine, and sanded with a calibrating sanding machine (with P80 grit sandpaper). First, their surface roughness values were measured; then, the specimens were processed in the machines in a radial and tangential process. Afterwards, the change in shear strength (adhesiveness resistance) was analyzed as a result of bonding with various adhesive types (PVAc, PU) and pressure applications (0.45 N/mm² or 0.9 N/mm²). Approximately 600 specimens were prepared with the purpose of identifying the effect of variables on the bonding performance, and they were subjected to shear testing. The greatest shear strength achieved for both the tangential and radial surfaces in terms of cutting was observed in specimens processed in the thickness machine, on which polyvinyl acetate adhesive and 0.9 N/mm. pressure were applied. Specimens bonded with polyvinyl acetate adhesive displayed higher shear strength in general in comparison to those bonded with polyurethane for both tangential and radial surfaces. [ABSTRACT FROM AUTHOR]

An experimental method was developed in this investigation to evaluate the shear strength of adhesive bonds in solid wood materials. The new method was tested against the standard test methods described in ASTM D-905, EN 205, and EN 302-1. Specimens were constructed of Oriental Beech (Fagus orientalis L.) and bonded with three different wood adhesives. Using the proposed method in the study, unintentional errors in cutting and testing processes of the shear specimens were decreased, which led to a decrease in the variability of the results. The worst stability was observed in the data obtained when the EN 205 and ASTM D-905 standard methods were used. [ABSTRACT FROM AUTHOR]

Tests were carried out to determine the bending moment capacities of Lshaped mortise and tenon furniture joints under both compression and tension loadings. The effects of wood species (Turkish beech and Scotch pine), adhesive type (polyvinylacetate and polyurethane), and tenon size (width and length) on the static bending moment capacity of joints under the same loading conditions were investigated. The results of the tests indicated that the moment capacity increased as either tenon width or length increased. The results also indicated that tenon length had a greater effect on the moment capacity than tenon width. In both compression and tension tests, Turkish beech joints were stronger than Scotch pine joints, and PU joints were stronger than PVA joints. An empirically derived expression was developed to estimate the average ultimate bending moment capacity of joints under compression and tension loads as functions of the wood species, the adhesive type, and the tenon size. [ABSTRACT FROM AUTHOR]

The elastic properties of oak wood (solid wood, scarf-jointed beams, and finger-jointed beams) and two different, independently applied adhesives (polyvinyl acetate and isocyanate) were investigated. Using a longitudinal vibration technique and comparing the elastic modulus of the solid wood and jointed beams, it was revealed that longer fingers (10 mm) in the finger joints and larger angle joints (70° and 75°) in the scarf-jointed beams enhanced the elastic properties of the beams. Based on these findings, it was concluded that these configurations result in elastic properties that are most similar to those of solid wood. The application of polyvinyl acetate rather than isocyanate significantly (P < 0.05) improved the elastic properties of the joints (both scarf- and finger-jointed beams). [ABSTRACT FROM AUTHOR]

The impact of fastener type (glued and unglued butterfly dovetail keys, glued and unglued H-shaped dovetail keys, one-pin dowel, two-pin dowels, and plywood spline) and wood composite material type on the bending moment capacity of L-shaped mitered frame joints under diagonal tension and compression loads was investigated. Specimens were constructed of laminated medium-density fiberboard (LamMDF) and laminated particleboard (LamPB). The glued joint specimens were constructed with polyvinyl acetate (PVAc) adhesive. In both tests, joints reinforced with two dowels had the highest bending moment capacity, whereas unglued joints fastened with H-shaped dovetail keys had the lowest capacity. Splined joints were characterized by the second highest bending moment capacity. Two-pin dowel joints had, on average, 47% greater capacity than one-pin dowel joints. The glued dovetail joints were 31% stronger than the unglued joints. There was no statistically significant difference between the bending moment capacities of butterfly and H-shaped dovetail keys. The LamMDF joints exhibited 7.8% greater capacity than joints constructed of LamPB. Overall, the bending moment capacity of joints loaded in compression was 22% higher than that of joints loaded in tension--when the moment arm in the compression specimens was taken at the inside corner of the joint. [ABSTRACT FROM AUTHOR]

The present research studied the acoustic properties of 40 oak timber samples (Quercus castaneifolia): the acoustic coefficient (K) and acoustic conversion efficiency (ACE) in free vibration mode, using the free-free bar method with different planes of vibration, i.e., tangential (LT) and radial (LR). These acoustic parameters were considered for both primary virgin wooden beams and modified beams carrying a single scarf joint in four different bonding angles (60°, 65°, 70°, and 75°), individually glued with two different adhesives (isocyanate and polyvinyl acetate). Comparing the acoustic properties of primary solid beams with scarf jointed beams of oak wood in LT and LR planes, the steeper joint angles of 70° and 75° did not result in any serious changes with polyvinyl acetate adhesive. Scarfjointed beams with smaller joint angles (60° and 65°) had significant effect on the acoustic properties relative to larger angles. Thus, beams having larger joint angles and beams glued using polyvinyl acetate may have enhanced acoustic properties. [ABSTRACT FROM AUTHOR]

A series of novel membrane materials were prepared based on liquefied banana pseudo-stem (LBPS) blended with various proportions of polyvinyl acetate emulsion (PVAc). The mechanical properties, structure, thermal stability, and cross-sectional morphologies were investigated using a universal testing machine, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. The addition of LBPS to PVAc led to a structural change, and this change depended on the reaction temperature. The enhancement of elongation and the thermostability of membranes is attributed to an increase in C-O-C groups. Furthermore, the LBPS/PVAc membranes have a higher water resistance. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the influence of varying temperature on the strength characteristics of joints bonded using three types of one-component PVAc adhesives (i.e., Rakoll Express D3, Titebond II Premium, and Rhenocoll 3W, 4B Plus) that belong to the group of thermoplastic wood adhesives intended for non-construction bonding applications. The measuring procedure was a transverse tensile test for estimation of joint strength. As documented by the test results, a higher joint strength achieved at a higher temperature was achieved again after a gradual increase in the joint temperature from 20 °C to 140 °C and subsequent cooling to the starting temperature. After cooling the joint to the starting temperature, all tested adhesives complied with the minimum strength, namely 10 MPa. The results obtained in this study indicated that the resistance and thus the strength of joints bonded using contemporary PVAc adhesives increases with time. [ABSTRACT FROM AUTHOR]

The effects of process parameters (adhesive spread, press time, and applied pressure) on the response parameter (shear strength) of pine wood bonded with PVAc were studied. Response surface methodology was applied for design of experiments and for analysis of results. A mathematical model was developed to establish the relationship between the process parameters and response parameters. The results showed that the major factors were adhesive spread and applied pressure. The shear strength increased as the adhesive spread and applied pressure increased within certain ranges. [ABSTRACT FROM AUTHOR]

Polyvinyl acetate (PVA) exhibits fine adhesion qualities when bonded to wood. However, when using thermo-treated wood, a number of different unstudied factors (such as the water stress condition) influence the wood bonding effectiveness. The main goal of this study was to evaluate how different treatments affect the shear bonding strength for three cases of thermo-vacuum treated woods. Wood from both Norway spruce (Picea abies Karst.) and common ash (Fraxinus excelsior L.) was thermo-treated at 190 °C for two hours under vacuum conditions (250 mbar). Turkey oak (Quercus cerris L.) logs were separately steamed at 110 °C for 24 h, then thermo-vacuum treated at 160 °C for three hours. The bonding shear strength between the PVA adhesive and treated wood was evaluated using water stress condition. The results were compared with the adhesive bond line properties of the untreated wood. The shear strength and wettability of the produced material were measured. Tests for the shear resistance, performed in accordance with the standard DIN EN 204, revealed dissimilar behavior as well as the influence of treatment schedules for the different wood species. Consequently, the tests performed allowed a detailed characterization of the effect of the thermovacuum process on the bonding quality of three common woods in different water stress conditions. [ABSTRACT FROM AUTHOR]

To predict the resin absorbing content of bamboo bundle fiber, a model relating to the soaking time and mass ratio of polyvinyl acetate (PVAC) adhesive to phenol formaldehyde (PF) resin defined on the basis of the Lucas-Washburn equation was proposed. Various dipping times and different PVAC/PF ratios were investigated in the experiment. Variance analysis revealed that the resin absorbing content was significantly associated with the ratio of PVAC/PF. However, the soaking time had a significant effect on bamboo fiber resin absorbing content from 0 s to 70 s and had an insignificant effect after 70 s. The results showed that the model proposed could accurately predict the resin absorbing content for bamboo bundle fiber impregnated in different PVAC/PF levels. The comparison of theoretical calculations with experimental results revealed that the residual sum of square and root mean squared error were relatively low, and the correlation coefficients and coefficients of determination were all over 0.95. [ABSTRACT FROM AUTHOR]

Chemical modification of wood with the aim of improving its dimensional stability can also influence the mechanical behavior of the timber when assembled into a structure. Hence, in this study, the stress-carrying capacity of mitred and butted L-type joints constructed from furfurylated wood samples with two weight percentage gains (WPGs), i.e., 20 and 60% (low and high levels, respectively), was investigated by subjecting the specimen to a diagonal tension load. Results indicated that the bending moment resistance of both L-type joints depends on the WPG. The L-type joints' bonded stress value with poly-vinyl acetate (PVAc) adhesive decreased with increasing WPGs. Likewise, in the case where epoxy adhesive was used for jointing, the stress capacity increased for both joints constructed with furfurylated wood. Values of tension stress in the butted joint were higher compared to the mitred one. Evaluation of shear stress parallel (T∥) and perpendicular (T⊥) to the grain of members jointed with PVAc adhesive demonstrated that the shear stress-carrying capacity decreases as furfurylation level increases. However, by applying epoxy adhesive for jointing, T∥ and T⊥ were increased by raising the furfurylation levels. [ABSTRACT FROM AUTHOR]

Bonding processes play a significant role in the wood and furniture industry. They allow for the creation of fixed joining of construction elements, creation of new materials and, last but not least, aesthetic appreciation of parts. However, the quality of bonded joints is affected by many factors, one of which is the moisture of the bonded material - wood. The main objective of this research was to determine the influence of wood moisture on the strength of bonded joints formed by polyvinyl acetate (PVAc) and polyurethane (PUR) adhesives. In current practice these adhesives are being increasingly used for their properties and zero formaldehyde content. The procedure for determining the bond strength (tensile shear strength of lap joints) corresponded to standard EN 205. It was ascertained that in addition to actual moisture of bonded wood, the quality of the joint is also affected by the environment to which the glued joint is subsequently subjected. In a normal environment, the strength of the tested joint PVAc adhesive decreases with increasing wood moisture, but it still meets the requirement of the standard. In a humid environment, the strength falls below the limit of the standardized value. In a normal environment the joint strength bonded with PUR adhesive is similar, but the decrease in strength is lower. In a humid environment it shows the highest strength at 20% wood moisture and meets the specified standard minimum strength (4 MPa). Graphs were created from the measured values that clearly show the influence of wood moisture on the final bond strength of a joint. [ABSTRACT FROM AUTHOR]

This study designed composite wooden construction elements strengthened with woven wire fiberglass netting and determined the technical attributes. Scots pine (Pinus sylvestris L.) was used in wooden layers, and woven wire fiberglass netting was used in intermediate layers. Layers were pressed with polyvinyl acetate (PVAc) D3 and Desmodur-VTKA adhesives to form 7 solid 13-layer laminated composite specimens. Experiments on 95 specimens determined density, bonding strength, bending resistance, and compression strength; solid and solid laminated wooden materials were tested and compared. BS EN 204 and BS EN 205 standards were complied with for bonding strength tests, TS 5497 EN 408 was used for densities, and TS 549 EN 408 was followed for bending resistance and compressive strength. Most factors, except for intermediate layer material in compressive strength and bending resistance tests perpendicular to the glue line, did not cause significant differences. Variables (adhesive, intermediate layer material) used for determining bending strength parallel to the glue line were effective. Polyurethane adhesive increased resistance to bending parallel to the glue line. These composite wooden construction elements supported with woven wire fiberglass netting could be advantageous for applications that require high bending resistance perpendicular to the glue line. However, these composites do not hold a compressive strength advantage. [ABSTRACT FROM AUTHOR]

Polyvinyl acetate (PVA) is commonly used to bond wood materials, but it generally exhibits poor performance when used in composites that require resistance to water and creep. However, it can be reinforced with different particles to improve its performance, making it useful for various applications. In this study, PVA was reinforced with cellulose fibers (CFs) at different loadings (1%, 2%, and 4%). A mixer was used to blend the PVA and CFs. Thermal properties and morphological structure of CFreinforced PVA adhesive were studied by thermogravimetric analysis (TGA/DTG) and scanning electron microscopy (SEM). The lap joint shear strength of woods bonded by CF reinforced PVA adhesive was tested on poplar and Scots pine woods that had 12% moisture content. The addition of CFs to PVA increased the thermal stability of PVA to different extents depending on the degree of loading on the CFs. The results of morphological studies indicated that some fluctuations on the SEM pictures were observed due to the dispersion of the CFs in the PVA matrix. The results showed that lap joint shear strength of the two different species of wood increased in all states after CFs were added to the PVA. [ABSTRACT FROM AUTHOR]

This research project deals with PVAc adhesives, their properties, and conditions of use. The primary objective of this study is to verify the dependence of the strength increase in a bonded joint on the curing time. The bonding process used the following PVAc adhesives: Kleiberit 303, Propellerleim 3W, 4B Plus, and Provotil, conforming to resistance classes D3 and D4 pursuant to ČSN EN 204. The test objects and processing of results were in accordance with ČSN EN 205. The readings were converted into charts demonstrating the strength increase in the bonded joints. The strength required in these adhesives by the standard is 10 MPa, and it is prescribed that the test should be performed over the 7 days following the assembly bonding (ČSN EN 204). The tested adhesives achieved this value in a time period of 75 min to 165 min, depending on the adhesive type. It also follows from the measurement that the results differ depending on the sort of adhesive. Comparison of the results with those of other authors (Košíček 1974; Eisner 1966; Eisner et al. 1983; Sedliačik 2005) indicates that the strength increase pattern is not changed with product development and that the differences are due to adhesive modifications by the manufacturers. [ABSTRACT FROM AUTHOR]

In this study, the elastic properties of 23 specimens of oak timber (Quercus castaneifolia), including the longitudinal modulus of elasticity (MOE), acoustic coefficient (K), and acoustic converting efficiency (ACE) in free vibration using the free-free beam method with different planes of vibration, i.e. tangential (LT) and radial (LR), were studied. These elastic parameters were examined in both sound wood and finger jointed timbers with two different lengths of fingers (5- and 10-mm finger lengths) and individually glued with two different types of adhesives (isocyanate and polyvinyl acetate). Comparing the elastic properties of solid beams with finger jointed beams of oak wood in both (LT) and (LR) planes, 10- mm finger joints with polyvinyl acetate adhesive did not cause any serious change to the studied elastic properties of the beams, while shorter finger length (5 mm) with isocyanate adhesive severely changed the acoustic properties; therefore, beams having longer finger lengths may have enhanced acoustical properties. [ABSTRACT FROM AUTHOR]

This study was aimed at determining the effects of the force loading direction on bending strength (MOR) and modulus of elasticity (MOE) in laminated wooden materials obtained in different compositions from cut veneers of Oriental beech and Lombardy poplar with thicknesses of 4 mm and 5 mm. A total of 180 experimental specimens were prepared for determining the MOR and MOE values in parallel and perpendicular directions to the glue line. The study involved a total of 6 air-dried density layer organizations of solid Oriental beech and Lombardy popular in 4 different laminate compositions and in the same dimensions, aimed at control. Polyvinyl Acetate (PVAc) and Polyurethane (PU) were used as the adhesive type in laminations with PVAc5-PU5-PVAc4-PU4. The specimens were subjected to bending strength and modulus of elasticity experiments in parallel and perpendicular directions to the glue line in accordance with the TS EN 310 standards. As a result of the statistical analysis of the data obtained at the end of the experiments, it was determined that in the laminated materials, the force loading direction in parallel or perpendicular to the glue line affected the MOR and MOE results. The best result in the laminated materials was found to be approximately 10% higher for MOR and MOE in a parallel direction to the PU4 glue line compared to the perpendicular direction. [ABSTRACT FROM AUTHOR]