- 5.1 Introduction
- 5.2 Material and Methods
- 5.3 Data Analysis
- 5.4 Results and Discussion
- 5.5 Conclusions
- 5.6 Literature Cited
- 5.7 List of Tables
- 5.8 List of Figures
There are ten species of larch ( Larix ) located mostly in colder climates in the northern hemisphere. Three larch species can be found in North America: the alpine larch ( Larix lyallii ) distributed primarily at high elevations in western Canada; the eastern larch ( Larix laricina ) distributed in boggy areas of the northern forests of eastern North America; and western larch ( Larix occidentalis ) distributed in the American West. The potential role of exotic larch in future sustainable fiber supply cannot be ignored since some introduced larch species such as Japanese larch ( Larix leptolepis ) and European larch ( Larix decidua ) often outperform Canadian native larch, pine, and spruce spieces and can produce two to three times more wood and fiber in the Lake States and southern parts of eastern Canada (Vallee and Stipanicic 1983; Fowler et al. 1988; Palmer 1991).
In this study, MDF panels were made from two individual exotic larch species Larix gmelinii and Larix sibirica . Species Larix sibirica is naturally distributed in west and central Siberia, Russia. Species Larix gmelinii has a larger natural distribution, dispersed from eastern Siberia to northeast China. These two species were introduced to northern Ontario, Canada in 1981. Seeding trials were established in six sites: Fort Frances, Kapuskasing, Ottawa, Espanola, Lindsay, and Huronia. A commercial thinning was carried out when the tree age was around 10-15 years, and the thinnings were collected and transported to Forintek Canada Corp. (Québec, Canada) for wood property characterization and panel manufacture. As a control, properties of MDF panels made from a mix of spruce, pine, and fir (S-P-F) were evaluated as well. S-P-F is a favorable material that is often utilized for MDF panel production in Québec, Canada. The aim of the study was to investigate the feasibility of using the two exotic larch species Larix gmelinii and Larix sibirica for MDF panel manufacturing.
LE, TS, and WA are important panel properties reflecting panel stabilities in length with changing relative humidity and either in thickness or in weight when the panel is soaked in water. The LE and TS of larch panels were significantly higher than those of panels made from S-P-F at the 0.05 significance level (Table 5-2). But there was no significant difference in WA between the two types of panels. In the ANSI A 208.2-2002 standard, there are no performance requirements for LE, TS, and WA. According to the maximum TS and WA properties specified by ANSI/AHA A 135.4-1995 (1995) for basic hardboard, which are 25 % and 35 %, respectively, TS and WA of the panels made from larch and S-P-F were below the maximum levels.
According to American National Standard (2002), MOR of panels made from larch and S-P-F wood chips both met the requirement of Grade 120. MOE of panels made from larch did not meet the ANSI minimum requirement, while MOE of panels made from S-P-F wood chips met the requirement of Grade 120. IB of larch panels met the requirement of ANSI Grade 140, but S-P-F panels met the requirement of Grade 120. Although MOR and MOE values of larch panels were lower than those of panels made from S-P-F, this difference can be compensated through optimizing hot-pressing parameters so as to acquire desirable panel density profile. In addition, attention should be paid to the refining process in order to produce larch fibers with less fine content. LE of panels made from larch was higher that that of panels fabricated from S-P-F, which may be a problem when the larch panels are applied to a moist environment.
American National Standards Institute (ANSI). Medium Density Fiberboard (MDF) for Interior Application . ANSI A 208.2-2002. Composite Panel Assoc., Gaithersburg. MD. 2002.
American Society of Testing and Materials (ASTM). Evaluating properties of wood-based fiber and particle panel materials . ASTM D 1037-99. Vol. 04.10. ASTM, Philadelphia. PA. Pp. 141-170; 2001.
Barnes, D. A. A model of the effect of fines content on the strength properties of oriented strand wood composites . Forest Prod. J. 52(5): 55-60; 2002.
Fowler, D. P., Simpson, J. D., Park, Y. S., and Schneider, M. H. Yield and wood properties of 25-year-old Japanese larch of difference provenance in eastern Canada . For. Chron. (12): 475-479; 1988.
Johns, W. E. and Niazi, K. A. Effect of pH and buffering capacity of wood on the gelation time of urea-formaldehyde resin . Wood Fiber Sci. 12(4): 255-263; 1980.
Li, M., Gertjejansen, R. O. and Ritter, D. C. Red pine thinnings as a raw material for waferboard . Forest Prod. J. 41(7/8): 41-43; 1991.
Maloney, T. M. Modern Particleboard & Dry-process fiberboard manufacturing . Updated edition. San Francisco. Miller Freeman Inc. 1993.
Palmer, C. L. Short-rotation culture of populus and larix: A literature review . Canada-Ontario For. Res. Dev. Agr. 65p; 1991.
Pugel, A. D., Price, E. W. and Hsu, C. Y. Composites from southern pine juvenile wood. Part 1: Panel fabrication and initial properties . Forest Prod. J. 40(1): 29-33; 1989.
SAS Institute, Inc. SAS/STAT User’s guide . Cary, N.C. 1990.
Shupe, T. F., Hsu, C. Y., Choong, E. T. and Groom, L. H. Effects of silvicultural practice and wood type on loblolly pine particleboard and medium density fiberboard properties . Holzforschung. 53(2): 215-222; 1999.
Tappi Standard. Fiber length of pulp by classification . T233cm-95. 1995.
Vallee, G. and Stipanicic, A. Growth and performance of larch plantations . Proceedings of a symposium sponsored by the Ontario Ministry of Natural Resources and the Faculty of Forestry, University of Toronto. Toronto, Ontario, Nov. 9, 1982. 1983.
Wang, S., Winistorfer, P. and Young, T. Fundamentals of vertical density profile formation in wood composites. Part III. MDF density formation during hot-pressing . Wood Fiber Sci. 36(1): 17-25; 2004.
Wang, S., Winistorfer, P. M., Young, T. M. and Helton, C. Step-closing pressing of medium density fiberboard. Part 1: Influences on the vertical density profile . Holz-als-Roh-und-Werkstoff. 59(1-2): 19-26; 2001.
Wang, S. and Winistorfer, P. M. Fundamentals of vertical density profile formation in wood composites . Part 2: Methodology of vertical density formation under dynamic conditions . Wood Fiber Sci. 32(2): 220-238; 2000.
Woodson, G. E. Effect of bark, density profile, and resin content on medium density fiberboards from Southern hardboards . Forest Prod. J. 26(2): 39-42; 1976.
Table 5-2 Density of larch and S-P-F wood chips, compaction ratio, average panel density, and properties of MDF panels.Numbers in columns ‘>3.240’, ‘0.828-3.240’, ‘0.281-0.828’, and ‘0.017-0.281’ were the percentages of fibers retained on the screens with mesh sizes of 3.240 mm2, 0.828 mm2, 0.281 mm2, and 0.017 mm2. Numbers in columns ‘<0.017’ were the percentages of fibers passed through the screen with mesh size of 0.017 mm2.
Methods described in Tappi 233 cm-95 were followed.
The means with the same letter were not significantly different by Duncan’s multiple range test at 0.05 of significance level.
Methods for panel density measurement were in accordance with ASTM D 1037-99.
Compaction ratios were based on density of panels equilibrated at 22 oC and 65 % RH and density of wood chips.
For further details log on website :