FROM LOG TO VENE,ER
4. Timber harvesting products are renewable
The Advantageous of Wood (4)
Timber originating from sustainably managed forests with appropriate forest management ensure a sustainable supply as long as the forest is sustainable.
Karakteristik Kayu sebagai Material Eco-Friendly
1.Kayu tersusun atas individual sel dan dengan dinding sel
SOFTWOODS AND HARDWOODS
f rees are roughly divided into soft- I woods and hardwoods, but the terms are inexact: Some hardwoods, such as basswood or aspen, for exam- ple, are softer than North American soft- woods like longleaf pine or Douglas-fir.
The type and shape of a tree's leaves are more accurate indicators of a particular wood's identity. Softwoods include evergreen conifers with needle- like leaves, while hardwoods comprise broad-leaved deciduous, or leaf-shed- ding, trees. But it is at the microscopic level that the true differences between softwoods and hardwoods can be seen.
Softwoods are composed mainly of tra- cheids, dual-purpose cells which con- duct the sap up through the trunk and
provide support. Hardwoods, which are believed to have evolved later, have nar- rowet thicker-walled fiber cells for sup- port and large-diameter thin-walled vessels for sap conduction, These cells determine thi texture of a tree's wood.
In spring, when there is abundant moisture and rapid growth of early- wood, the tracheid cells in softwoods have thin walls and large cavities to con- duct the sap. The result is relatively porous wood. As latewood develops in the latter part of the growing season, the tracheids begin to form thicker walls, creating denser wood.
In hardwoods such as oak or ash, most of the vessels develop in the early- wood, resulting in uneven grain. These
species are called ring-porous. With dif- fuse-porous hardwoods such as maple, the vessels are distributed more evenly in the earlpvood and latewood. Some species, such as walnut, exhibit a more gradual transition from earlpvood to latewood and are termed semi-rine- porous or semi-diffuse-porous.
The differences in cell structure between softwoods and hardwoods become apparent when a stain is applied.
In softwoods, the light, porous early- wood absorbs stain more readily than the dark, denser latewood-in effect reversing the grain pattern like a photo- graphic negative. Hardwoods, however, absorb stain more evenly, enhancing the
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(above, right),the sap is conducted through vessels, a series of tubelike cells stacked one atop the other. Support for the trunk is provided by f iber cells. In the ring-porous hardwood shown, vessels are more prominent in earlywood; f ibers are the pre- dominant cell type in latewood. In both hardwoods and soft- woods, storage cells for carbohydrates and starch make up the remainins non-vascular wood tissue.
CELL STRUCTURE ()F SOFTWOODS AND HARDW()()DS
Latewood
A microscopic view
The differences between softwood and hardwood are readily apparent when viewed under a microscope's magnif ication.
The cell structure of softwoods (above, /eff) is much simpler than that of hardwoods. Almost all softwood cells are long, thin tracheids, which support an unbroken column of sap that can tower more than 200 feet. The tracheids in Iatewood become thrcker-walled than those in earlvwood. In hardwoods
T6
Karakteristik Kayu sebagai Material Eco-Friendly
52 Saka
FIGURE 1 The gross structure of a typical softwood tracheid or hardwood fiber. (Courtesy of Prof. Emer. R. J. Thomas, North Carolina State University, Raleigh, NC.)
wall layers. Instead, the gelatinous layer (G layer) is usually deposited adjacent to the cell lumen (Fig. 2c). The G layer contains little or no lignin and consists mainly of cellulose microfibrils oriented parallel to the fiber axis.
111. CHEMICAL COMPOSITION OF WOOD A. Normal Wood and Reaction Wood
The chemical constituents of wood are well known, and a number of authors have provided an excellent review of this work [4-81. The major cell wall constituents are cellulose, hemicelluloses, and lignin. Other polymeric constituents, present in lesser and often var- ying quantities, are starch, pectin, and ash for the extractive-free wood.
Tables 1 and 2 show comparisons of the chemical composition made by Time11 [9]
for five hardwoods and five softwoods, respectively. Although the cellulose content is more or less the same (43 -t 2%) for both groups, the hardwoods contain less lignin. The lignin content of hardwoods is usually in the range of 18-25%, whereas that of softwoods varies between 25% and 35%. However, tropical hardwoods can exceed the lignin content of many softwoods. The structure of lignin is different between these two groups: softwood lignins are composed mostly of guaiacyl units, whereas hardwood lignins consist of sy- ringyl and guaiacyl moieties [ 101.
The hemicelluloses found in these groups vary both in structure and quality, as shown in Fig. 3. The predominant hardwood hemicellulose is a partly acetylated, glucuronoxylan (O-acetyl-4-O-methylglucuronoxylan), accounting for 20-35%, whereas softwoods con- tain glucuronoarabinoxylan (arabino-4-0-methylglucuronoxylan) in the range of 10%.
Hardwoods contain only a small quantity of glucomannan. In softwoods, however, a partly acetylated galactoglucomannan (0-acetylgalactoglucomannan) makes up as much as 18%.
In addition to these major cell wall components, pectic materials and starch are included in much smaller quantities in both softwoods and hardwoods. Ash usually makes up between 0.1% and 0.5% of wood, but tropical species often exceed this range. Wood
52 Saka
FIGURE 1 The gross structure of a typical softwood tracheid or hardwood fiber. (Courtesy of Prof. Emer. R. J. Thomas, North Carolina State University, Raleigh, NC.)
wall layers. Instead, the gelatinous layer (G layer) is usually deposited adjacent to the cell lumen (Fig. 2c). The G layer contains little or no lignin and consists mainly of cellulose microfibrils oriented parallel to the fiber axis.
111. CHEMICAL COMPOSITION OF WOOD A. Normal Wood and Reaction Wood
The chemical constituents of wood are well known, and a number of authors have provided an excellent review of this work [4-81. The major cell wall constituents are cellulose, hemicelluloses, and lignin. Other polymeric constituents, present in lesser and often var- ying quantities, are starch, pectin, and ash for the extractive-free wood.
Tables 1 and 2 show comparisons of the chemical composition made by Time11 [9]
for five hardwoods and five softwoods, respectively. Although the cellulose content is more or less the same (43 -t 2%) for both groups, the hardwoods contain less lignin. The lignin content of hardwoods is usually in the range of 18-25%, whereas that of softwoods varies between 25% and 35%. However, tropical hardwoods can exceed the lignin content of many softwoods. The structure of lignin is different between these two groups: softwood lignins are composed mostly of guaiacyl units, whereas hardwood lignins consist of sy- ringyl and guaiacyl moieties [ 101.
The hemicelluloses found in these groups vary both in structure and quality, as shown in Fig. 3. The predominant hardwood hemicellulose is a partly acetylated, glucuronoxylan (O-acetyl-4-O-methylglucuronoxylan), accounting for 20-35%, whereas softwoods con- tain glucuronoarabinoxylan (arabino-4-0-methylglucuronoxylan) in the range of 10%.
Hardwoods contain only a small quantity of glucomannan. In softwoods, however, a partly acetylated galactoglucomannan (0-acetylgalactoglucomannan) makes up as much as 18%.
In addition to these major cell wall components, pectic materials and starch are included in much smaller quantities in both softwoods and hardwoods. Ash usually makes up between 0.1% and 0.5% of wood, but tropical species often exceed this range. Wood
Semua kayu strukturnya selluler dengan dinding sel yang terdiri dari campuran selulosa,
karbohidrat nonselulosa dan lignin, yang tersusun sebagai suatu matrix diperkuat.
Karakteristik Kayu sebagai Material Eco-Friendly
(2)2.Kayu bersifat anisotropis
Kayu menunjukkan sifat
fisik & mekanik yang
berbeda yang berbeda
jika diuji pada tiga sumbu
arah utamanya.
Karakteristik Kayu sebagai Material Eco-Friendly
(2)2.Kayu bersifat anisotropis
Karakteristik Kayu sebagai Material Eco-Friendly
(3)3.Kayu bersifat higroskopis
Kayu dapat kehilangan atau menyerap air sebagai akibat dari
perubahan kelembaban dan suhu atmosfir.
Karakteristik Kayu sebagai Material Eco-Friendly
(4)4.Kayu dapat dibiodegradasi
Kayu dapat dibiodegradasikan oleh serangan organisme jamur/fungi, bakteri, dan serangga tertentu. Sifat ini
merupakan peluang untuk memproduksi bioenergi
Karakteristik Kayu sebagai Material Eco-Friendly
(5)5.Kayu dapat dibakar
Jika kayu digunakan sebagai bahan bangunan ringan, sifat kemudah-
terbakarannya harus diperhitungkan. Sifat ini membuat kayu menjadi salah satu dari sumber bahan bakar utama
Kayu bakar Bencana kebakaran rumah
Karakteristik Kayu sebagai Material Eco-Friendly
(6)6.Kayu sangat lembam terhadap bahan kimia
Kayu sesuai untuk pemanfaatan di industri yang sangat memerlukan ketahanan terhadap bahan kimia dan korosi. Namun demikian jika kayu dikenai keadaan udara (atmosfir), karena pengaruh cuaca akan secara berangsur-angsur terkikis dengan laju pengikisan sekitar 6 – 7 mm per abadnya. Keadaan yang biasanya dapat dengan mudah dicegah
dengan cara pengecatan permukaannya; perlindungan yang juga menambah keunggulan dekoratif dan mengurangi porositas
permukaannya.
Karakteristik Kayu sebagai Material Eco-Friendly
(7)7.Kayu sangat awet
Di tempat dengan kondisi yang tak sesuai bagi agen perusak, kayu dapat digunakan dengan sangat tahan
A.D. 604
The oldest wooden building in the world (Horyuji, Japan)
The oldest wooden building in Korea (Bongjeongsa)
11 Century
(Prof. Nam-Hun.Kim)
Karakteristik Kayu sebagai Material Eco-Friendly
(8)8.Kayu bersifat isolator
Strukturnya yang berserat dan banyaknya udara yang dapat
diperangkap membuat kayu memiliki sifat isolasi yang baik. Kecuali kayu, bahan bangunan yang digunakan untuk rumah umumnya bukan merupakan isolator yang baik.
Kehilangan panas dibanding kayu :
Batubata 6 kali
Kaca jendela 8 kali Beton dari pasir 15 kali
Baja 390 kali
Aluminium 1700 kali
Concrete Wood
Cold radiant heat Warm radiant heat
Karakteristik Kayu sebagai Material Eco-Friendly
(8)8.Kayu bersifat isolator
(Prof. Nam-Hun.Kim)
Pengenalan jenis kayu
• Indonesia memiliki kurang lebih 4.000 jenis kayu
• Jenis kayu komersial penting sekitar 400 jenis
• Diperlukan teknik pengenalan jenis kayu untuk memberi kepastian dalam perdagangan kayu
• Perlindungan jenis: menghindari ilegal trading, penyelundupan, dll. WOOD IDENTIFICATION KEYS
A collection of labeled wood samples can be invaluable in helping you b ecome familiar with a variety of woods. It may also contain a species
you wish to identify.
I orrectly identifying an unfamiliar
\; wood sample out of thousands of possibilities requires close observation, and a thorough knowledge ofwood and its properties. But as a practical matter, the possible choices are usuallylimited to several familiar species, and a commer- cially available set of labeled wood sam- ples, such as the one shown at right, may include a piece that matches the wood you are attempting to identifr. Most often, however, you will need to record the features of a sample, then use a wood identification key from a book to make sense ofyour results.
An identification key is essentially a master list of woods and their proper- ties that serves as a cross-reference to link the features of a particular sample to a species name. Some keys require that you compare their entries against features that are visible to the naked eye or with a 10x magnifier, while others demand that you note microscopic details. Still other keys are based on the user having wide-ranging sensory infor- mation about the wood, including its colot odor and texture, and the bark and leaf shape of the tree from which it came.
Using a key is like climbing the branches of a tree. You are asked to answer a series of paired statements, choosing the one that best describes the wood in question and proceeding to the next pair indicated. At each statement, the user forks onto a different branch
until reaching a leaf that identifies the sample. The first statement may involve the texture of the wood. If the wood is porous, for example, you are sent to one set of statements; if it is non-porous, you jump to a different set of statements. You continue this way, flipping from page to page in a book, as each answer gradual- lyreduces the choices. Finally, the search is narrowed to a single species.
Avoid keys that try to cover every wood species in the world; they will prove too general. Choose one that describes trees in a specific region, such as North American softwoods or tropical hard- woods. Several classic keys can be found in woodworking boola; check your local library or boolstore. Some public agen-
cies (below) also offer wood identifica- tion services.
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SOURCES FOR WOOD IDEI{TIFICATIOI{
Books
Edlin, Herbert L., What Wood ls That?
A Manual of Wood ldentification.
New York: Viking, 1969.
Hoadley, Bruce, ldentifying Wood.
Nevvton, Connecticut: Tau nton Press, 1990.
Panshin, A.J. and DeZeeuw, Carl,Textbook of Wood Technologr.
New York: McGraw Hill, 1980.
Rendfe, 8.J., World Timbers: Volumes 1-3. London: Ernest Benn, 1970.
Sharp, John 8., Wood ldentification:
A Manual for The Non-Profexional.
Knoxville: University of Tennessee
Agricultural Extension Service, Forestry and Wildlife Extension, 1990.
Timber Research Development Association, Timbers of the World:
Volumes I and 2. Lancaster;
Construction Press, 1979.
Agencies that offer wood identification services
Center For Wood Anatomy Research U.S. Forest Products Laboratory 1 Gifford Pinchot Drive
Madison, Wisconsi n 53705-2398 International Wood Collectors Societv 2913 Third Street
Trenton, Michigan 48183
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