Iranian Journal of Wood and Paper Science Research
Year:2000 | Volume:- | Issue:11|Papers Count:2

In this study, the effect of board type, press time and resin content on the strength of particleboard have been evaluated. The boards made for this study contained bagasse and logging residues of Eucalyptus wood particles at a 50 to 50 ratio and employed Urea formaldehyde (UF) resin as the binder. Variable factors are as follows:- type of board; single layer, three layer- press time; 5 , 6 , 7 , minutes- resin content; 9 , 10 , 11 percentThree boards' were manufactured for each combination of variables. Samples of all the boards made were tested by the methods described in DIN 68763 standard to obtain mean values of bending strength, and internal bond strength (LB). In addition samples of each type of board were tested for thickness swelling after immersion in water for 2 hours and 24 hours respectively.The results of this study show clearly that three layer particleboard has significantly higher bending strength than single layer, but single layer boards have better properties from the physical aspect. Increasing the content of U.F resin from 9 per cent to 10 per cent was found to reduce the thickness swelling, and tended to improve the strength properties of the board, in both single layer and three layer boards. Press time has significant effect on bending strength and I.B Highest MOR and MOE were observed on three layer board pressed for 7 minutes.

Eight-nineteen-year-old trees from Eucalytus steriaticalyx from Dehnow experimental Plantation located 160 Km. South west of Shiraz were selected randomly and fell two from each of the four blocks. From each tree, 10 cm thick cross-sectional discs at several different heights (3 meters intervals) were cut and together with remaining boles then transferred to the Alborz Research Center-Karaj for laboratory studies. The laboratory studies included determination of physical, anatomical and mechanical properties as well as chemical compositions of wood.The mechanical properties were evaluated on the ASTM samples for air-dry and green conditions. The following conclusions were drawn from this study:E. steriaticalyx from one site in southern region of Iran has an average specific gravity of 0.935, fiber length of 0.881 mm, fiber diameter of 16.063 m, lumen diameter of 4.465 m, cell wall thickness 5.789 m, cellulose content of 47.07 percent.It was found that the mean values of modulus of rupture, modulus of elasticity and compression strength-parallel to grain tested at green condition were 67.35 MPa, 8649 MPa and 35.36 MPa and air- condition were 117.53 MPa, 13397 MPa and 72.31 MPa respectively.Data are also presented on other mechanical properties such as impact strength, nail withdrawal cleavage and etc.