Properties Of Laminated Veneer Lumber Research Articles

Improved strength properties of LVL glued using PVAc adhesives with physical treatment-based Rubberwood (Hevea brasiliensis)

Abstract The properties of the laminated veneer lumber (LVL) composed of the boiled veneer of Rubberwood (Hevea brasiliensis) using polyvinyl acetate (PVAc) adhesives in various cold-pressing time and various conditioned time with loaded and unloaded were studied. Five-ply LVL was produced by boiling veneer at 100°C for 90 min as pretreatment and cold-pressing time at 12 kgf cm−2 for 1.5, 6, 18, and 24 h then conditioned at 20°C and 65% relative humidity (RH) with loaded (12 kgf cm−2) and unloaded for 7 days as physical treatment. Especially for the delamination test, the specimens were immersed at 70 ± 3°C for 2 h and dried in the oven at 60 ± 3°C for 24 h; then, the specimens were solidified at room temperature (20°C and 65% RH) with loaded (12 kgf cm−2) and unloaded for 7, 10, 12, and 14 days. To determine the performance of LVL, the density, moisture content (MC), delamination, modulus of elasticity (MOE), modulus of rupture (MOR), horizontal shear strength, and formaldehyde emission tests were conducted according to the Japanese Agricultural Standard (JAS 2008) for structural LVL. The MOE and MOR values were significantly influenced by the physical treatment, however, neither to horizontal shear strength nor to formaldehyde emission. The best performance of LVL has resulted from unloaded LVL with cold-pressed time for 18 h; the MOE and MOR values were 9,345.05 ± 141.61 N mm−2 and 80.67 ± 1.77 N mm−2, respectively. The best value of the horizontal shear strength was obtained from the LVL with 18 h cold-pressing time and conditioned with loaded (13.10 ± 1.47 N mm−2) and unloaded (12.23 ± 1.36 N mm−2). The percentage of delamination values decreased with an increase in the cold-pressing time and conditioning time. The lowest value of delamination (19.06%) was obtained from the LVL with 24 h cold-pressing time and conditioned with loaded for 14 days. Except the delamination test, all other properties fulfilled the JAS.

Properties of red maple laminated veneer lumber impregnated with waterborne micronized and two soluble copper formulations

ABSTRACTCertain important quality parameters of red maple (Acer rubrum) laminated veneer lumber (LVL) impregnated with three waterborne formulations: copper azole (CA-B), micronized copper azole (MicroCA or MCA) and alkaline copper quaternary (ACQ-D) bonded with phenol formaldehyde or cross-linked polyvinyl acetate (XPVAc) adhesives were evaluated. Pre-dipping of veneers before LVL production and two post-manufacturing procedures, viz., vacuum-pressure and post-dipping of LVL, were applied. Maximum copper retention in pre-dip-treated, vacuum-pressure and post-dip-treated LVL was 1.4, 9.7 and 1.7 kg/m3, respectively. Copper retention in MCA-treated LVL was relatively lower than soluble formulations. Various physical, mechanical and bonding properties of treated LVL such as density, water absorption, swelling, flexural properties, hardness, tensile shear strength, delamination and wood failure (%) were studied and compared with untreated LVL. Little to negligible deleterious effect was observed on properties of LVL due to these chemical treatments. Analysis of variance results showed that most of properties of red maple LVL were not significantly different compared with those of untreated LVL. Therefore, vacuum-pressure impregnation process can be used to treat the red maple LVL with novel micronized copper formulations for increasing the service life of such products against biodegradation without affecting techno-mechanical quality parameters.

Effects of Veneer Treatment with Copper-Based Preservatives on the Decay Resistance and Mechanical Properties of Poplar LVL

To improve the durability of poplar laminated veneer lumber (LVL), the veneers were impregnated with alkaline copper quaternary (ACQ) and copper azole (CA) at four retention levels, and the effects of the treatments on the LVL properties were examined. The results demonstrated that the treatments substantially improved the decay resistance of LVLs, with the decreases in mass losses ranging from 42.6% to 87.3%. However, retention levels greater than the specified standard values for Use Category C4.1 might be required for sufficient protection of poplar LVL against decay fungi. The bending and shear properties of all treated LVLs met the requirements for high-grade products specified in the LVL standard GB/T 20241. No significant effects of the treatments were observed on the mechanical properties of LVLs, and the LVLs did not display any visible delamination after boil-dry treatment. These results imply that the treatments significantly improved the decay resistance of poplar LVL products and had no appreciable impact on their mechanical and physical properties.

Engineered Wood Composite of Laminated Veneer Lumber: Physical and Mechanical Properties

Utilisation of forest plantation species such as Acacia hybrid has been used in wood-based industry as an alternative to solid wood that was usually attained from natural forest. While, the under-utilised species such as Mangifera sp. is not often been used as raw material for wood products, in this study, laminated veneer lumber (LVL) has been produced from Acacia hybrid and Mangifera sp. The physical and mechanical properties of LVL were determined and compared. For physical testing, the range value of moisture content was 9.41% to 14.56%, Density was 487.90 kg/m3 to 699.10 kg/m3, thickness swelling was between 0.20% to 6.05%, water absorption between 32.71% to 91.25%, and rate of delamination from 0% to 100%. Mangifera sp. LVL has higher moisture content, rate of delamination, and water absorbency. In mechanical testing, it is been found that Acacia hybrid LVL has overall higher strength compared to Mangifera sp. LVL, in terms of static bending strength (MOR and MOE), shear strength, and compression strength. Range of value for MOR was between 10.27 N/mm2 to 129.99 N/mm2, MOE between 1138 N/mm2 to 16472.93 N/mm2, shear strength between 0.43 N/mm2 to 3.40 N/mm2, and compression between 139.45 N/mm2 to 6749.74 N/mm2. For physical testing, the overall result of p-value for moisture content, water absorption, and delamination were significant at p ≤ 0.05, while density and thickness swelling were not significant at p ≥ 0.05. For overall result, the p-value for static bending strength (MOR and MOE) was significant at p ≤ 0.05 while for shear strength and compression strength were not significant at p ≥ 0.05.

Effects of grading of veneers on properties of LVL made from Schizolobium amazonicum Huber ex. Ducke

The work aimed at evaluating the influence of pre-classification of veneer made from parica (Schizolobium amazonicum Huber ex. Ducke) plantation trees on Laminated Veneer Lumber (LVL) properties. This species is native to the Amazonian and is fast growing with low density. For LVL production, veneers were separated into four classes according to the density or dynamic modulus of elasticity. LVL was produced considering three different strategies of assembly—random veneers assembly; assembly using veneers with greater EMd placed at the surface layer with gradual reduction up to the center of the panels; assembly using veneers with greater density placed at the surface layer and gradual reduction into the center of the panels. The following mechanical and physical properties were then evaluated: static bending modulus of elasticity (EM), modulus of rupture (fM), compression strength parallel to grain (fc0), shear strength parallel to glue-line (fv0), shear strength perpendicular to glue-line (fv90), water absorption and thickness swelling for 2 and 24 h of water immersion. Physical properties of LVL were not found to be influenced by different pre-classification strategies, while for mechanical properties only bending strength at flatwise position was influenced by pre-classifying veneers.

Influence of veneer thickness on the properties of LVL from Paricá (Schizolobium amazonicum) plantation trees

The work aimed at evaluating the influence of the veneer thickness on physical and mechanical properties of laminated veneer lumber (LVL) boards made from Schizolobium amazonicum plantation trees. It is a fast growing species (20 m3/ha/year), having a straight trunk almost without any branch and producing a white-yellowish low density hardwood: usually <0.40 g/cm3. The boards were manufactured with the following thicknesses: 1.54, 2.32 and 2.71 mm. Seven LVL boards were produced for each thickness, totaling 21, all according to the following characteristics: PVAc adhesive (200 g/m2), pressed (1.0 N/mm2) at room temperature for 12 h. The following mechanical and physical properties were then evaluated: static bending modulus of elasticity (EM), modulus of rupture (fM), compression strength parallel to grain (fc,0), shear strength parallel to glue-line (fv,0), shear strength perpendicular to glue-line (fv,90), water absorption and thickness swelling for 2 and 24 h of water immersion. The results pointed out that the utilization of thinner veneers implied improving mechanical properties, while thicker veneer reduced the water absorption. Nevertheless, in contrast, the efficiency was lower than that observed when thicker veneer was used.

Study on the Effect of Impregnation Process on Physical and Mechanical Properties of Chinese Fir LVL

Laminated veneer lumber (LVL) was manufactured from Chinese fir, which had been impregnated with laboratory prepared low-molecular-weight water-soluble phenol formaldehyde (PF) resin. The effects on the mechanical and physical properties of the LVL were investigated which made from veneer that had been subjected to various levels of the resin treatment. The results showed that either under conditions of normal temperature and pressure, or at increased pressure, the weight gain would increase with the impregnating time. Under the same impregnation technology, along with the increase of resin concentration, dry weigh gain increased, wet weight gain first increased and then decreased. Density of LVL increased, TS reduced, MOR and MOE first increased and then decreased as the weight gain increased.

Study on the Technology and Properties of Soybean Adhesive Bonded Laminated Veneer Lumber from Poplar Wood

It was investigated that the technology of hot prepressing temperature and hot pressing duration had influence on the mechanical and physical properties of soybean adhesive bonded laminated veneer lumber(LVL) from poplar wood. The results show that lower mat prepressing temperature may be beneficial to the mechanical properties of LVL. The effects of hot pressing duration on the properties of LVL are less than those of prepressing temperature. When the prepressing temperature is 70°C and hot pressing time is 100s/mm with glue spread amount of 450g/m2, hot pressing temperature of 160°C and mat pressure of 1.6 MPa, the mean modulus of rupture value is 78 MPa, mean modulus of elasticity value is 14.4 GPa, mean horizontal shear strength value is 7.8 MPa and immersion peel rate is 0.4%, respectively.

Laminated veneer lumber (LVL) manufacturing using three hybrid poplar clones

Laminated veneer lumbers (LVLs) were manufactured from veneers of 3 rotary peeled fast growing hybrid poplar clones, I-214 (Populus ×euramericana), I-77/51 (Populus deltoides), and S.307-26 (Populus deltoides), with a phenol formaldehyde (PF) adhesive. Two Populus deltoides clones that are grown in Turkey were used for the first time in LVL production. The clone effect on selected LVLs' physical, mechanical, and combustion properties were investigated and compared to those of host woods (HWs). In addition, the suitability of 2 new Populus deltoides clones in addition to Populus ×euramericana was determined for LVL manufacturing. The properties of LVLs were affected by clone types. Populus deltoides clones had better physical, mechanical, and combustion properties compared to those of Populus ×euramericana. This could be attributed to the higher density and fiber length values of Populus deltoides clones. S.307-26 clone had the highest and I-214 had the lowest physical, mechanical, and combustion properties among 3 different hybrid poplar clones. Contribution factor, compaction factor or densification, improvement rate, manufacturing technique, and LVL technology were counted among the reasons for the higher LVLs' properties compared to those of HWs. The findings of the present research may be used to increase the use of fast growing poplar wood for value added products, i.e. LVLs by providing scientific data.