PROPERTIES OF LAMINATED VENEER LUMBER MANUFACTURED FROM HEAT TREATED VENEER

The objective of this study was to determine and compare properties of laminated veneer lumber (LVL) panels manufactured from heat treated (212o C, 2h) and untreated pine veneer with melamine urea formaldehyde (MUF) adhesive. The results showed that, heat treatment considerably decreased all investigated physical properties of LVL. The reductions in density (D), moisture content (MC), and thickness swelling (TS) were 8.33%, 33.78% and 14.03%, respectively. The findings of this study demonstrated that heat treatment resulted in adverse effect on bending strength and hardness of LVL panels. Heat treatment caused a decrease in bending strength (MOR) by 31.85% and in hardness (HT) by 25.44%. However, modulus of elasticity (MOE) and compressive strength (CS) values of LVL panels were higher than those of untreated groups. Compressive strength and modulus of elasticity (MOE) of LVL panels made of heat treated veneer respectively were 11.17% and 7.46% higher than untreated LVL

Effects of Manufacturing Conditions on the Properties of Boric Acid/Melamine-Urea-Formaldehyde Microcapsules Prepared By in situ Polymerization: Its Inhibition Behavior on Wood Destroying Fungi

Water-soluble boric acid (BA) was microencapsulated by in situ polymerization with a melamine-urea formaldehyde shell. The effects of core-shell ratio, time, and temperature on the microcapsule characteristics were investigated. The microencapsulated BA was tested for its effectiveness against wood-destroying fungi. The results showed that the core:shell ratio affected the individuality of the microcapsules (MCs), and the most individual microcapsules were those with the 1:1 core:shell ratio. The microencapsulation temperature at the 1:1 core:shell ratio affected the surface porosity and size spectrum of MCs. The surface was porous, and the size spectrum was narrow at 50 °C. The microencapsulation reaction time at the 1:1 core-shell ratio did not have a considerable effect on the MC size. Although the MC size spectrum varied in the studied parameters (core: shell ratio, temperature, time), the average MC sizes were large enough to pass through the bordered pits of the softwood cell wall. Slow boron release was obtained by optimizing the MC preparation parameters. The optimum microencapsulation parameters for slow release of BA were the 1:1 core:shell ratio, 50 °C, and time of 120 min. The capsules produced at optimum microencapsulation parameters were biologically active against the fungus Coniophora puteana and leaching resistance was improved

SHEAR STRENGTH OF HEAT-TREATED TALI (ERYTHROPHLEUM IVORENSE) AND IROKO (CHLOROPHORA EXCELSA ) WOODS, BONDED WITH VARIOUS ADHESIVES

The aim of this study was to evaluate the effect of heat treatment on the shear strength of tali (Erythrophleum ivorense) and iroko (Chlorophora excelsa) woods, bonded with some structural adhesives. Shear strength of untreated and heat-treated woods bonded with phenol-formaldehyde (PF), melamine-urea-formaldehyde (MUF), melamine-formaldehyde (MF), and polyurethane (PUR) adhesives was studied. An industrial heat treatment method (ThermoWood) was used. The timbers were thermally modified for 2 hours at 180 ºC. Laminated samples having two sample sets were prepared from untreated and heat-treated wood for the shear strength test. The results of the tests showed that the heat treatment affected shear strength of laminated wood negatively. Although there was a considerable difference in adhesive bond shear strength between untreated and treated wood, both wood species bonded with the adhesives fulfilled the required value for shear strength of the adhesive bonds. PF, MUF, MF, and PUR adhesives performed in a rather similar way for both wood species