Wood compression

T. E. TimeU, iu Compression Wood in Gymnsperms, Vol. 1, Springer Vedag, New York, 1985, Chapt. 5. 

Other distinct classes of wood in a tree include the portion formed in the first 10—12 years of a tree s growth, ie, juvenile wood, and the reaction wood formed when a tree s growth is distorted by external forces. Juvenile fibers from softwoods are slightly shorter and the cell walls thinner than mature wood fibers. Reaction wood is of two types because the two classes of trees react differentiy to externally applied stresses. Tension wood forms in hardwoods and compression wood forms in softwoods. Compression wood forms on the side of the tree subjected to compression, eg, the underside of a leaning tmnk or branch. Tension wood forms on the upper or tension side. Whereas in compression wood, the tracheid cell wall is thickened until the lumen essentially disappears, in tension wood, tme fiber lumens are filled with a gel layer of hemiceUulose. 

Countertops of compressed wood fiber have the advantage of low cost. Although their resistance to chemicals and some liquid spills... 

Kim, Y. S. and Singh, A. P. (1999). Micromorphological characteristics of compression wood degradation in waterlogged archaeological pine wood. Holzforschung 53 381-385. 

Inoue, M., Norimoto, M., Tanahashi, M. and RoweU, R.M. (1993a). Steam or heat fixation of compressed wood. Wood and Fiber Science, 25(3), 224—235. 

Seborg, R.M., Millett, M.A. and Stamm, A.J. (1945). Heat-stabilized compressed wood (Staypak). Mechanical Engineering, 67(1), 25-31. 

Stamm, AJ. and Seborg, R.M. (1941). Resin-treated, compressed wood. Transactions of the American Institute of Chemical Engineers, 37, 385-397. 

A further development of static methods of hardness testing was a method devised by Brinell (1900), which consisted of driving a steel ball into the mineral to be tested for hardness under a pressure of 29.4 kN for about 30 seconds. Brinell hardness is defined as the ratio of load to surface of round indentation. The method has found wide use in engineering—for metals it is excellent, but in mineralogy it has proved unsatisfactory because of the high brittleness of most minerals and their non-deformability under the action of the steel ball. The ever wider application of Brinell s method and of a similar method developed by Janko in hardness determination of wood (Krzysik, 1974) should be noted. They are most useful in testing hard wood-base materials, such as compressed wood. 

For building my son s bed frame and bookshelving, I am planning on using a compressed wood board that has no formaldehyde Medite II by SierraPine (wwwsierrapine. 

Compressed wood-phenolic-formaldehyde composite. Dried treated wood compressed during curing to collapse cell structure Density 1.3 to 1.4. ASE about 95%... 

Heat stabilized compressed wood. Wood heated to 320°C. then compressed 400 to 4000 psi, then cooled and pressure released. Handles and desk legs. 

They have prepared some compressed wood samples which show, in addition to increased density and surface hardness, a lower moisture regain than untreated wood up to 80% relative humidity. Using materials such as these, they have experimented with the manufacture of parquet flooring, a rather severe test of dimensional stability. A variety of other finished products have been prepared, some on pilot plant scale. However, it is not known to what extent they have appeared as products in the open market. Their technology is available through licensure. 

Fig. 1-18. Transverse section of compression wood tracheids in tamarack (Larix laricina), showing intercellular spaces (IS), middle lamella (M), the outer (S,), and the inner (S2) layer of the secondary wall, and the lumen (L). The So layer contains narrow, branched helical cavities (HC) as well as two wide drying checks (C), an artifact. Transmission electron micrograph. Courtesy of Dr. T. E. Timell.

Compression wood is heavier, harder, and denser than the normal wood. Its tracheids are short and thick-walled (even in earlywood) and in cross section rounded so that empty spaces remain between the cells. The S, layer is thicker than in a normal wood while the S J layer is absent. The layer contains helical cavities that parallel the microfibrils and reach from the... 

Tension wood differs less from normal wood than compression wood. It contains thick-walled fibers, terminated towards the lumen by a gelatinous layer (Fig. 1-19). This so-called G layer consists of pure and highly crystalline cellulose oriented in the same direction as the fiber axis. For this reason the cellulose content of tension wood is higher and the lignin content lower than in normal wood. 

Timell, T. E. (1973). Ultrastructure of the dormant and active cambial zones and the dormant phloem associated with formation of normal and compression woods in P/ cea abies (Karst.). Tech. Publ.—State Univ. N.Y., Coll. Environ. Sci. For., Syracuse No. 96, pp. 1 -23. 

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