Effect of thermo-mechanical refining on properties of MDF made from black spruce bark |
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Authors: | Cheng Xing James Deng S Y Zhang |
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Institution: | (1) Tennessee Forest Products Center, University of Tennessee, 2506 Jacob Dr., Knoxville, TN 37996-4570, USA;(2) Forintek Canada Corp., 319 rue Franquet, G1P 4R4 Quebec City, QC, Canada |
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Abstract: | The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black
spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different
refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either
0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical
blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters.
Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was
used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship
between panel properties and the two test factors. The results from this study indicated that the preheating retention time
was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant
factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water
absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure.
Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m3 had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark
residues can be considered as a potentially suitable raw material for manufacturing MDF products. |
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