Advertisement

Holz als Roh- und Werkstoff

, Volume 63, Issue 6, pp 397–402 | Cite as

Effect of grain orientation and surface wetting on vertical density profiles of thermally compressed fir and spruce

  • J.Y. Wang
  • P.A. CooperEmail author
ORIGINALARBEITEN ORIGINALS

Abstract

The effects of grain orientation and surface wetting on wood densification by compression in a hot press were evaluated for two commercial Canadian wood species, balsam fir (Abies balsamea) and black spruce Picea mariana. The vertical density profiles (VDP) of wood densified at 180 °C could be engineered to achieve different properties depending on press closing rate, wood permeability and annual ring orientation. The lower permeability of spruce caused it to split frequently during hot pressing. For balsam fir, at a press closing time of 2 min, the compressed wood with an original grain angle of 0° (radial compression) shows widened high density bands due to collapse of low density earlywood adjacent to the dense latewood. All grain orientations show higher density areas close to the wood surfaces similar to those of wood-based composites. However, when wood was preheated without pressure for 5 min followed by a press closing time of 2 min, water migrated to and plasticized the board centre causing it to be densified while the surface density remained low. Wood surface plasticizing with water or urea solution causes some localized surface densification, but the effect was not great.

Keywords

Closing Time Grain Orientation Wood Surface Radial Compression Wood Composite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Einfluss der Jahrringstellung und der Oberflächenbefeuchtung auf das Rohdichteprofil von thermisch verdichtetem Tannen- und Fichtenholz

Zusammenfassung

An zwei kanadischen Nutzhölzern, Balsam fir (Abies balsamea) und Black spruce ( Picea mariana) wurde untersucht, wie sich die Jahrringstellung und eine Oberflächenbefeuchtung auf die Verdichtung dieser Hölzer in einer Heisspresse auswirkt. Über die Querschnittshöhe kann ein unterschiedliches Rohdichteprofil erzeugt werden. In Abhängigkeit der Presszeit, der Permeabilität und der Jahrringstellung der Hölzer konnten bei einer Verdichtung bei 180 °C unterschiedliche Dichteprofile (VDP) erzeugt werden. Die geringe Permeabilität von Fichtenholz führte während des Heisspressens häufig zum Aufspalten. Bei Tannenholz, das mit einer Presszeit von 2 min. und einer Jahrringstellung von 0 °C (Druck in radialer Richtung) verdichtet wurde, bildeten sich durch den Kollaps des an Spätholz angrenzenden Frühholzes verbreiterte Bereiche hoher Dichte. Bei allen Jahrringstellungen bildete sich wie bei plattenförmigen Holzwerkstoffen ein Rohdichteprofil mit erhöhter Dichte an den Oberflächen aus. Wenn das Holz jedoch 5 min. lang ohne Druck vorgeheizt und dann bei einer Presszeit von 2 min. verdichtet wurde, diffundierte das Wasser nach innen. Der innere Bereich des Holzes plastifizierte und verdichtete sich dadurch, während sich die oberflächennahen Schichten weniger stark verdichteten. Eine Plastifizierung der Holzoberflächen mit Wasser oder Harnstofflösung ergab eine örtlich begrenzte, nicht stark ausgeprägte Oberflächenverdichtung.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Bodig J (1963) The peculiarity of compression of conifers in radial direction. Forest Prod J 13:438Google Scholar
  2. 2.
    Bodig J (1965a) The effect of anatomy on the initial stress-strain relationship in transverse compression. Forest Prod J 15(5):197–202Google Scholar
  3. 3.
    Bodig J (1965b) Effect of growth characteristics on the mechanical properties of Douglas-fir in radial compression. Holzforschung 19(3):83–88CrossRefGoogle Scholar
  4. 4.
    Bodig J (1966) Stress-strain relationship for wood in transverse compression. J Mater 1(3):645–666Google Scholar
  5. 5.
    Bodig J, Jayne BA (1982) Mechanics of Wood and Wood Composites. Van Nostrand Reinhold Company, New York, AmericaGoogle Scholar
  6. 6.
    Currier RA (1963) Compressibility and bond quality of western softwood veneers. Forest Prod J 13:71–80Google Scholar
  7. 7.
    Dai C, Steiner PR (1993) Compression behavior of randomly formed wood flake mats. Wood Fiber Sci 25(4):349–358Google Scholar
  8. 8.
    Dwianto W, Morooka T, Norimoto M (1998) The compressive stress relaxation of Albizia (Paraserienthes falcata Becker) wood during heat treatment (in Japanese with English abstract). Mokuzai Gakkaishi 44(6):403–409Google Scholar
  9. 9.
    Dwianto W, Morooka T, Norimoto M, Kitajima T (1999) Stress relaxation of sugi (Cryptomeria japonica D. Don) wood in radial compression under high temperature steam. Holzforschung 53:541–546CrossRefGoogle Scholar
  10. 10.
    Dwianto W (1999) Mechanism of permanent fixation of radial compressive deformation of wood by heat or steam treatment [Dissertation]. Japan Wood Research Institute, Kyoto University, KyotoGoogle Scholar
  11. 11.
    Inoue M, Norimoto M, Otsuka Y, Yamada T (1990) Surface compression of coniferous wood lumber.. A new technique to compress the surface layer. Mokuzai Gakkaishi 36(11):969–975Google Scholar
  12. 12.
    Inoue M, Norimoto M, Tanahashi M, Rowell RM (1993a) Steam or heat fixation of compressed wood. Wood Fiber Sci 25(3):224–235Google Scholar
  13. 13.
    Inoue M, Ogata S, Kawai S, Rowell RM, Norimoto M (1993b) Fixation of compressed wood using melamine-formaldehyde resin. Wood Fiber Sci 25(4):404–410Google Scholar
  14. 14.
    Inoue M (1993) Transverse compression deformation of wood and its permanent fixation [Dissertation]. Japan Wood Research Institute, Kyoto University, KyotoGoogle Scholar
  15. 15.
    Inoue M, Minato K, Norimoto M (1994) Permanent fixation of compressive deformation of wood by crosslinking. Mokuzai Gakkaishi 40(9):931–936Google Scholar
  16. 16.
    Kamke FA, Casey LJ (1988) Fundamentals of flakeboard manufacture: internal-mat conditions. Forest Prod J 38(6):38–44Google Scholar
  17. 17.
    Kennedy RW (1968) Wood in transverse compression-Influence of some anatomical variables and density on behavior. Forest Prod J 18(3):36–40Google Scholar
  18. 18.
    King EG (1961) Time-dependent strain behavior of wood in tension parallel to the grain. Forest Prod J 11:156–165Google Scholar
  19. 19.
    Kunesh RH (1961) The inelastic behavior of wood: A new concept for improved panel forming processes. Forest Prod J 11:395–406Google Scholar
  20. 20.
    Lenth CA, Kamke FA (1996) Investigations of flakeboard mat consolidation / characterization the cellular structure. Wood Fiber Sci 28(2):159–167Google Scholar
  21. 21.
    Liu YX, Norimoto M, Morooka T (1993) The large compressive deformation of wood in the transverse direction 1: Relationships between stress-strain diagrams and specific gravities of wood. Mokuzai Gakkaishi 39(10):1140–1145Google Scholar
  22. 22.
    Norimoto M (1993) Large compressive deformation in wood (in Japanese). Mokuzai Gakkaishi 39(8):867–874Google Scholar
  23. 23.
    Norimoto M (1994) Heat treatment and steam treatment of wood (in Japanese). Wood Ind 49(12):588–592Google Scholar
  24. 24.
    Schniewind AP (1959) Transverse anisotropy of wood: A function of gross anatomic structure. Forest Prod J 9:350–359Google Scholar
  25. 25.
    Seborg RM, Millett MA, Stamm AJ (1945) Heat-stabilized compressed wood-(Staypak). Mech Eng 67:25–31Google Scholar
  26. 26.
    Shamaev VA, El’kov LV, Popova NI (1975) Stabilization of wood modified with urea (in Russian). Izv VUZ, Lesnoi Zh 18(5):97–101Google Scholar
  27. 27.
    Stamm AJ, Harris EE (1953) Chemical processing of wood. Chemical Publishing Co, Inc, New York, America, pp 205–261Google Scholar
  28. 28.
    Stamm AJ (1964) Wood and Cellulose Science. Ronald Press, New York, pp 317–358Google Scholar
  29. 29.
    Strickler MD (1959) Effect of press cycle and moisture content on properties of Douglas-fir flakeboard. Forest Prod J 9(7):203–215Google Scholar
  30. 30.
    Tabarsa T, Chui YH (1997) Effects of hot-pressing on properties of white spruce. Forest Prod J 47(5):71–76Google Scholar
  31. 31.
    Tabarsa T, Chui YH (2000) Stress-strain response of wood under radial compression. Test method and influence of cellular properties. Wood Fiber Sci 32(2):144–152Google Scholar
  32. 32.
    Tabarsa T, Chui YH (2001) Characterizing microscope behavior of wood under transverse compression. Effect of species and loading direction. Wood Fiber Sci 33(2):223–232Google Scholar
  33. 33.
    Wang JY, Zhao GJ (1999) The mechanism of formation, recovery and permanent fixation of wood set (in Chinese with English abstract). J Beijing For Univ 21(3):71–77Google Scholar
  34. 34.
    Wang JY, Zhao GJ, Iida I (2000) Effect of oxidation on heat fixation of compressed wood of China fir. For Stud China 2(1):73–79CrossRefGoogle Scholar
  35. 35.
    Wang JY (2000) Fixation of compressed wood of Chinese fir by heat treatment and gamma irradiation [Dissertation]. Beijing Forestry University, ChinaGoogle Scholar
  36. 36.
    Wang JY, Zhao GJ (2001) Fixation and creep of compressed wood of Chinese fir irradiated with gamma rays. For Stud China 3(1):58–65Google Scholar
  37. 37.
    Wang S, Winistorfer PM (2000) Fundamentals of vertical density profile formation in wood composites. Part 2. Methodology of vertical density formation under dynamic conditions. Wood Fiber Sci 32(2):220–238Google Scholar
  38. 38.
    Winistorfer PM, Young TM, Walker E (1996) Modeling and comparing vertical density profiles. Wood Fiber Sci 28(1):133–141Google Scholar
  39. 39.
    Winistorfer PM, Moschler WW, Wang S, Depaula E, Bledsoe BL (2000) Fundamentals of vertical density profile formation in wood composites. Part 1. In-situ density measurement of the consolidation process. Wood Fiber Sci 32(2):209–219Google Scholar
  40. 40.
    Wolcott MP, Kamke FA, Dillard DA (1990) Fundamentals of flakeboard manufacture: Viscoelastic behavior of the wood components. Wood Fiber Sci 22(4):345–361Google Scholar
  41. 41.
    Wong ED, Zhang M, Wang Q, Kawai S (1999) Formation of the density profile and its effects on the properties of particleboard. Wood Fiber Sci 33(2):327–340CrossRefGoogle Scholar
  42. 42.
    Youngs RL (1957) Mechanical properties of red oak related to drying. Forest Prod J 7:315–324Google Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Faculty of ForestryUniversity of TorontoTorontoCanada

Personalised recommendations