Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an constituent material – a natural composite of cellulose fibers that are strong in latent hostility and embedded in a matrix of lignin that resists compression. wood is sometimes defined as only the secondary xylem in the stems of trees, [ 1 ] or it is defined more broadly to include the lapp type of tissue elsewhere such as in the roots of trees or shrubs. [ citation needed ] In a live corner it performs a support function, enabling woody plants to grow big or to stand up by themselves. It besides conveys water and nutrients between the leaves, early growing tissues, and the roots. wood may besides refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber. wood has been used for thousands of years for fuel, as a construction fabric, for making tools and weapons, furniture and newspaper. More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
Reading: Wood – Wikipedia
As of 2005, the growing store of forests worldwide was about 434 billion cubic meters, 47 % of which was commercial. [ 2 ] As an abundant, carbon-neutral [ citation needed ] renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991 approximately 3.5 billion cubic meters of wood were harvested. dominant uses were for furniture and build construction. [ 3 ]
history
A 2011 discovery in the canadian province of New Brunswick yielded the earliest sleep together plants to have grown wood, approximately 395 to 400 million years ago. [ 4 ] [ 5 ] wood can be dated by carbon paper date and in some species by dendrochronology to determine when a wooden object was created. People have used wood for thousands of years for many purposes, including as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and composition. Known constructions using wood date back ten-spot thousand years. Buildings like the european Neolithic hanker house were made primarily of wood. holocene use of wood has been enhanced by the addition of steel and bronze into construction. [ 6 ] The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevail climate at the time a tree was cut. [ 7 ]
physical properties
Diagram of secondary growth in a corner display idealized vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the bow, existing branches and roots, to form a growth ring
Growth rings
wood, in the rigid feel, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire bow, living branches, and roots. This process is known as secondary growth ; it is the solution of cellular telephone division in the vascular cambium, a lateral meristem, and subsequent expansion of the new cells. These cells then go on to form thickened secondary cell walls, composed chiefly of cellulose, hemicellulose and lignin. Where the differences between the four seasons are clear-cut, e.g. New Zealand, growth can occur in a discrete annual or seasonal convention, leading to growth rings ; these can normally be most clearly seen on the conclusion of a log, but are besides visible on the early surfaces. If the disparateness between seasons is annual ( as is the case in equatorial regions, e.g. Singapore ), these growth rings are referred to as annual rings. Where there is small seasonal dispute growth rings are likely to be indistinct or lacking. If the bark of the tree has been removed in a especial sphere, the rings will probable be deformed as the plant overgrows the scar. If there are differences within a emergence ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is normally composed of broad elements. It is normally lighter in color than that near the outer assign of the hoop, and is known as earlywood or springwood. The out part formed later in the season is then known as the latewood or summerwood. [ 8 ] however, there are major differences, depending on the kind of wood ( see below ). If a tree grows all its life in the open and the conditions of territory and locate remain unchanged, it will make its most rapid growth in young person, and gradually decline. The annual rings of growth are for many years quite wide, but late they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from class to year, the rings must necessarily become dilutant as the trunk gets wider. As a tree reaches adulthood its crown becomes more assailable and the annual wood production is lessened, thereby reducing inactive more the width of the growth rings. In the encase of forest-grown trees so much depends upon the competition of the trees in their fight for light and nourishment that periods of rapid and behind increase may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the hale, however, as a tree gets larger in diameter the width of the growth rings decreases .
Knots
A knot on a tree trunk As a tree grows, lower branches often die, and their bases may become overgrow and enclosed by subsequent layers of proboscis wood, forming a type of imperfection known as a knot. The dead outgrowth may not be attached to the trunk forest except at its base, and can drop out after the tree has been sawn into boards. Knots affect the technical properties of the wood, normally reducing the local force and increasing the tendency for splitting along the wood grain, [ citation needed ] but may be exploited for ocular impression. In a longitudinally saw plank, a ravel will appear as a approximately circular “ hearty ” ( normally dark ) objet d’art of wood around which the granulate of the rest of the wood “ flows ” ( parts and rejoins ). Within a nautical mile, the commission of the wood ( grain direction ) is up to 90 degrees different from the grain direction of the regular forest. In the tree a slub is either the basis of a side branch or a dormant bud. A slub ( when the base of a side branch ) is conic in human body ( hence the roughly round cross-section ) with the inside tip at the point in shank diameter at which the plant ‘s vascular cambium was located when the branch formed as a bud. In grading log and morphologic forest, knots are classified according to their form, size, soundness, and the steadiness with which they are held in place. This steadiness is affected by, among other factors, the length of time for which the branch was abruptly while the attaching stem continued to grow .
Wood knot in erect section
Knots materially affect cracking and warping, ease in working, and cleavability of timber. They are defects which weaken timber and lower its value for structural purposes where strength is an important consideration. The weakening effect is much more serious when timber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression. The extent to which knots affect the strength of a beam depends upon their position, size, number, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. If there is a season check in the knot, as is often the case, it will offer little resistance to this tensile stress. Small knots, however, may be located along the neutral plane of a beam and increase the strength by preventing longitudinal shearing. Knots in a board or plank are least injurious when they extend through it at right angles to its broadest surface. Knots which occur near the ends of a beam do not weaken it. Sound knots which occur in the central portion one-fourth the height of the beam from either edge are not serious defects.Samuel J. Record, The Mechanical Properties of Wood[9]
Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the healthy wood than upon localize defects. The dampen intensity is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain. In some cosmetic applications, forest with knots may be desirable to add ocular interest. In applications where wood is painted, such as skirt boards, fascia boards, door frames and furniture, resins present in the forest may continue to ‘bleed ‘ through to the surface of a knot for months or even years after manufacture and read as a yellow or brown stain. A knot primer paint or solution ( knotting ), correctly applied during homework, may do much to reduce this trouble but it is unmanageable to control completely, specially when using mass-produced kiln-dried lumber stocks .
Heartwood and sapwood
“ heartwood ” redirects here. For other uses, see Heartwood ( disambiguation ) 
A section of a Yew branch showing 27 annual growth rings, pale sapwood, dark heartwood, and kernel ( center darkness spotlight ). The night radial lines are little knots. Heartwood ( or duramen [ 10 ] ) is wood that as a result of a naturally occurring chemical transformation has become more insubordinate to decay. Heartwood formation is a genetically program process that occurs spontaneously. Some doubt exists as to whether the wood dies during heartwood formation, as it can distillery chemically react to decay organisms, but entirely once. [ 11 ] The condition heartwood derives entirely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart wholly decayed. Some species begin to form heartwood identical early in life sentence, then having only a thin layer of alive sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, sugarberry, beech, and pine, blockheaded sapwood is the rule. [ 12 ] Some others never form heartwood. Heartwood is frequently visually distinct from the living sapwood, and can be distinguished in a cross-section where the limit will tend to follow the emergence rings. For exercise, it is sometimes much dark. however, early processes such as decay or worm invasion can besides discolor wood, flush in woody plants that do not form heartwood, which may lead to confusion. Sapwood ( or alburnum [ 13 ] ) is the younger, outermost forest ; in the growing corner it is living forest, [ 14 ] and its chief functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. however, by the clock time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is beginning formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the book of sapwood required. Hence trees making rapid growth in the afford have thicker sapwood for their size than trees of the same species growing in dense forests. sometimes trees ( of species that do form heartwood ) originate in the open may become of considerable size, 30 curium ( 12 in ) or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines .
cross-section of an Oak Log Showing Growth Rings No definite relation back exists between the annual rings of emergence and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are constrict, more of them are required than where they are broad. As the corner gets larger, the sapwood must inevitably become slender or increase materially in volume. Sapwood is relatively thick in the upper share of the trunk of a tree than near the basis, because the age and the diameter of the upper sections are less. When a tree is very young it is covered with limbs about, if not entirely, to the grind, but as it grows older some or all of them will finally die and are either break in off or fall off. subsequent growth of wood may wholly conceal the stub which will however remain as knots. No count how smooth and clear a log is on the outside, it is more or less knotty near the middle. consequently, the sapwood of an previous tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the forest and interfere with its rest of working and other properties, it follows that a given firearm of sapwood, because of its position in the tree, may well be stronger than a part of heartwood from the like tree. different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is bad and fledged. In some trees, the wood laid on late in the liveliness of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a bombastic logarithm the sapwood, because of the time in the life of the tree when it was grown, may be inferior in unfeelingness, potency, and temper to equally sound heartwood from the lapp log. In a smaller tree, the reversion may be on-key .
color
In species which show a distinct difference between heartwood and sapwood the lifelike color of heartwood is normally darker than that of the sapwood, and very frequently the contrast is conspicuous ( see segment of yew log above ). This is produced by deposits in the heartwood of chemical substances, so that a dramatic semblance variation does not imply a significant deviation in the mechanical properties of heartwood and sapwood, although there may be a mark biochemical remainder between the two. Some experiments on very pitchy longleaf pine specimens indicate an increase in potency, due to the resin which increases the force when dry. such resin-saturated heartwood is called “ fatness light ”. Structures built of fat light are about impervious to rot and termites ; however they are very flammable. Stumps of old longleaf pines are frequently jab, split into small pieces and sold as kindling for fires. Stumps frankincense excavate may actually remain a hundred or more since being cut. Spruce impregnated with blunt resin and dried is besides greatly increased in strength thereby. Since the latewood of a growth ring is normally darker in semblance than the earlywood, this fact may be used in visually judging the density, and therefore the hardness and lastingness of the material. This is particularly the event with coniferous woods. In ring-porous woods the vessels of the early wood often appear on a finished surface as dark than the dense latewood, though on hybrid sections of heartwood the reversion is normally true. Otherwise the tinge of wood is no reading of lastingness. abnormal stain of forest frequently denotes a diseased stipulate, indicating unsoundness. The total darkness check in western hemlock is the consequence of insect attacks. The red-brown streaks sol coarse in hickory and certain other woods are by and large the result of injury by birds. The stain is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which therefore become diagnostic of weakness ; however an attractive consequence known as spalting produced by this process is frequently considered a desirable characteristic. average sap-staining is due to fungal growth, but does not inevitably produce a dampen effect .
Water content
Water occurs in living wood in three locations, namely :
- in the cell walls,
- in the protoplasmic contents of the cells
- as free water in the cell cavities and spaces, especially of the xylem
In heartwood it occurs only in the first and last forms. wood that is thoroughly air-dried retains 8–16 % of the water in the cell walls, and none, or much none, in the other forms. even oven-dried wood retains a modest share of moisture, but for all exclude chemical purposes, may be considered absolutely dry. The general effect of the body of water content upon the wood meaning is to render it softer and more elastic. A like consequence occurs in the softening action of water on rawhide, paper, or fabric. Within sealed limits, the greater the body of water content, the greater its softening impression. Drying produces a distinct increase in the lastingness of wood, particularly in small specimens. An extreme example is the case of a wholly dry spruce block 5 curium in section, which will sustain a permanent lode four times equally bang-up as a park ( undried ) obstruct of the same size will. The greatest force increase due to drying is in the ultimate crush potency, and strength at elastic limit in endways compression ; these are followed by the modulus of tear, and try at elastic specify in cross-bending, while the modulus of elasticity is least moved. [ 9 ]
structure
Magnified cross-section of black walnut, showing the vessels, rays ( white lines ) and annual rings : this is intermediate between diffuse-porous and ring-porous, with vessel size declining gradually wood is a heterogenous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose ( 40–50 % ) and hemicellulose ( 15–25 % ) impregnated with lignin ( 15–30 % ). [ 15 ] In coniferous or softwood species the wood cells are largely of one kind, tracheids, and as a result the material is much more undifferentiated in structure than that of most hardwoods. There are no vessels ( “ pores ” ) in coniferous forest such as one sees indeed prominently in oak and ash, for model. The structure of hardwoods is more building complex. [ 16 ] The urine conducting capability is by and large taken care of by vessels : in some cases ( oak, chestnut, ash ) these are quite big and distinct, in others ( horse chestnut, poplar, willow ) besides little to be seen without a bridge player lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous. [ 17 ] In ring-porous species, such as ash, bootleg locust, catalpa, chestnut, elm, hickory, mulberry, and oak, [ 17 ] the larger vessels or pores ( as cross sections of vessels are called ) are localized in the function of the growth ring formed in spring, therefore forming a region of more or less open and porous tissue. The rest of the gang, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give military capability and huskiness to wood, while the vessels are a generator of helplessness. [ citation needed ] In diffuse-porous woods the pores are evenly sized therefore that the urine conducting capability is scattered throughout the growth ring alternatively of being collected in a isthmus or row. Examples of this kind of wood are alder, [ 17 ] linden, [ 18 ] birch, [ 17 ] ohioan, maple, willow, and the Populus species such as aspen, cottonwood and poplar. [ 17 ] Some species, such as walnut and cerise, are on the border between the two classes, forming an intermediate group. [ 18 ]
Earlywood and latewood
In softwood
Earlywood and latewood in a softwood ; radial position, emergence rings closely spaced in Rocky Mountain Douglas-fir In moderate softwoods, there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope, the cells of dense latewood are seen to be very thick-walled and with very humble cell cavities, while those formed first in the season have thin walls and large cell cavities. The lastingness is in the walls, not the cavities. Hence the greater the proportion of latewood, the greater the concentration and strength. In choosing a piece of pine where lastingness or awkwardness is the authoritative consideration, the star thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not about so authoritative as the proportion and nature of the latewood in the ring. If a heavy assemble of ache is compared with a lightweight nibble it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is consequently showing more intelligibly demarcate growth rings. In ashen pines there is not much contrast between the different parts of the resound, and as a solution the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decide contrast to the soft, straw-colored earlywood. It is not alone the proportion of latewood, but besides its timbre, that counts. In specimens that show a identical big symmetry of latewood it may be perceptibly more porous and count well less than the latewood in pieces that contain less latewood. One can judge relative density, and consequently to some extent potency, by ocular inspection. No satisfactory explanation can as even be given for the accurate mechanisms determining the formation of earlywood and latewood. several factors may be involved. In conifers, at least, rate of growth entirely does not determine the proportion of the two portions of the gang, for in some cases the wood of dense increase is very hard and big, while in others the opposition is truthful. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where potency or ease of working is all-important, woods of moderate to slow increase should be chosen .
In ring-porous woods
Fraxinus excelsior; tangential view, wide growth rings Earlywood and latewood in a ring-porous wood ( ash ) in a ; tangential opinion, broad growth rings In ring-porous woods, each season ‘s increase is always well defined, because the big pores formed early in the season border on the dense tissue of the year earlier. In the character of the ring-porous hardwoods, there seems to exist a pretty definite relation back between the rate of growth of timbre and its properties. This may be concisely summed up in the general argument that the more rapid the increase or the wide-eyed the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of run, subject to some exceptions and limitations. In ring-porous woods of commodity growth, it is normally the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slowly growth produces relatively inner light, holey wood composed of thin-walled vessels and wood parenchyma. In beneficial oak, these big vessels of the earlywood invade from 6 to 10 percentage of the volume of the log, while in inferior corporeal they may make up 25 % or more. The latewood of dear oak is iniquity discolor and firm, and consists largely of thick-walled fibers which form one-half or more of the woodwind. In subscript oak, this latewood is much reduced both in measure and choice. such version is very largely the resultant role of rate of growth. Wide-ringed wood is much called “ second-growth ”, because the growth of the unseasoned forest in capable stands after the honest-to-god trees have been removed is more rapid than in trees in a closed forest, and in the fabricate of articles where military capability is an important consideration such “ second-growth ” hardwood material is preferred. This is peculiarly the sheath in the choice of hickory for handles and spokes. here not alone strength, but huskiness and resilience are significant. [ 9 ] The results of a series of tests on hickory by the U.S. Forest Service show that :
- “The work or shock-resisting ability is greatest in wide-ringed wood that has from 5 to 14 rings per inch (rings 1.8-5 mm thick), is fairly constant from 14 to 38 rings per inch (rings 0.7–1.8 mm thick), and decreases rapidly from 38 to 47 rings per inch (rings 0.5–0.7 mm thick). The strength at maximum load is not so great with the most rapid-growing wood; it is maximum with from 14 to 20 rings per inch (rings 1.3–1.8 mm thick), and again becomes less as the wood becomes more closely ringed. The natural deduction is that wood of first-class mechanical value shows from 5 to 20 rings per inch (rings 1.3–5 mm thick) and that slower growth yields poorer stock. Thus the inspector or buyer of hickory should discriminate against timber that has more than 20 rings per inch (rings less than 1.3 mm thick). Exceptions exist, however, in the case of normal growth upon dry situations, in which the slow-growing material may be strong and tough.”[19]
The effect of rate of increase on the qualities of chestnut forest is summarized by the lapp authority as follows :
- “When the rings are wide, the transition from spring wood to summer wood is gradual, while in the narrow rings the spring wood passes into summer wood abruptly. The width of the spring wood changes but little with the width of the annual ring, so that the narrowing or broadening of the annual ring is always at the expense of the summer wood. The narrow vessels of the summer wood make it richer in wood substance than the spring wood composed of wide vessels. Therefore, rapid-growing specimens with wide rings have more wood substance than slow-growing trees with narrow rings. Since the more the wood substance the greater the weight, and the greater the weight the stronger the wood, chestnuts with wide rings must have stronger wood than chestnuts with narrow rings. This agrees with the accepted view that sprouts (which always have wide rings) yield better and stronger wood than seedling chestnuts, which grow more slowly in diameter.”[19]
In diffuse-porous woods
In the diffuse-porous woods, the line between rings is not always so authorize and in some cases is about ( if not entirely ) invisible to the unaided eye. conversely, when there is a clear line there may not be a detectable remainder in structure within the growth ring. In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring alternatively of collected in the earlywood. The consequence of rate of growth is, consequently, not the same as in the ring-porous woods, approaching more closely the conditions in the conifers. In general, it may be stated that such woods of medium growth afford stronger material than when very quickly or identical lento grown. In many uses of wood, sum potency is not the main retainer. If facilitate of working is prized, wood should be chosen with respect to its uniformity of texture and directness of grain, which will in most cases occur when there is little contrast between the latewood of one season ‘s increase and the earlywood of the following .
Monocot woodwind
Trunks of the coconut palm, a monocot, in Java. From this perspective these look not a lot unlike from trunks of a dicot or conifer geomorphologic fabric that resembles ordinary, “ dicot ” or conifer timber in its megascopic cover characteristics is produced by a number of monocot plants, and these besides are colloquially called wood. Of these, bamboo, botanically a member of the grass syndicate, has considerable economic importance, larger culms being widely used as a building and construction material and in the industry of mastermind floor, panels and veneer. Another major implant group that produces material that much is called wood are the palms. Of much less importance are plants such as Pandanus, Dracaena and Cordyline. With all this material, the structure and composition of the process raw material is quite different from ordinary wood .
particular graveness
The single most disclosure place of wood as an indicator of wood quality is particular graveness ( Timell 1986 ), [ 20 ] as both pulp give way and log lastingness are determined by it. specific gravity is the proportion of the multitude of a substance to the multitude of an equal volume of water system ; density is the proportion of a mass of a measure of a meaning to the bulk of that measure and is expressed in mass per unit message, for example, grams per milliliter ( g/cm3 or g/ml ). The terms are basically equivalent ampere hanker as the system of measurement system is used. Upon drying, wood shrinks and its density increases. minimal values are associated with greens ( water-saturated ) wood and are referred to as basic specific gravity ( Timell 1986 ). [ 20 ]
Wood density
Wood concentration is determined by multiple emergence and physiological factors compounded into “ one fairly easily measured forest characteristic ” ( Elliott 1970 ). [ 21 ] Age, diameter, stature, radial ( luggage compartment ) growth, geographic localization, locate and growing conditions, silvicultural discussion, and sow source all to some degree influence wood concentration. variation is to be expected. Within an individual tree, the variation in wood concentration is often equally great as or even greater than that between different trees ( Timell 1986 ). [ 20 ] Variation of specific gravity within the bole of a tree can occur in either the horizontal or upright direction .
Tabulated physical properties
The take after tables list the mechanical properties of woodwind and lumber implant species, including bamboo. wood properties : [ 22 ] [ 23 ]
Bamboo properties : [ 24 ] [ 23 ]
Hard versus soft
It is coarse to classify wood as either softwood or hardwood. The wood from conifers ( e.g. pine ) is called softwood, and the wood from dicotyledons ( normally broad-leaved trees, e.g. oak ) is called hardwood. These names are a snatch deceptive, as hardwoods are not inevitably hard, and softwoods are not inevitably voiced. The well-known balsa ( a hardwood ) is actually softer than any commercial softwood. Conversely, some softwoods ( e.g. yew ) are harder than many hardwoods. There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. [ citation needed ] The density of woodwind varies with species. The density of a wood correlates with its force ( mechanical properties ). For example, mahogany is a medium-dense hardwood that is excellent for fine furniture craft, whereas balsa is light, making it useful for model build. One of the densest woods is black rose chestnut .
chemistry
Chemical structure of lignin, which makes up about 25 % of woodwind dry topic and is responsible for many of its properties. The chemical writing of wood varies from species to species, but is approximately 50 % carbon, 42 % oxygen, 6 % hydrogen, 1 % nitrogen, and 1 % other elements ( chiefly calcium, potassium, sodium, magnesium, iron, and manganese ) by weight. [ 25 ] Wood besides contains sulphur, chlorine, silicon, phosphorus, and other elements in little quantity. aside from water, wood has three main components. Cellulose, a crystalline polymer derived from glucose, constitutes about 41–43 %. following in abundance is hemicellulose, which is around 20 % in deciduous trees but near 30 % in conifers. It is chiefly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third part at around 27 % in coniferous wood vs. 23 % in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between the lignin and the hemicellulose. A major focus of the newspaper industry is the interval of the lignin from the cellulose, from which newspaper is made. In chemical terms, the dispute between hardwood and softwood is reflected in the writing of the part lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is chiefly derived from coniferyl alcohol. [ 26 ]
Extractives
away from the structural polymers, i.e. cellulose, hemicellulose and lignin ( lignocellulose ), wood contains a large variety show of non-structural constituents, composed of low molecular system of weights organic compounds, called extractives. These compounds are confront in the extracellular quad and can be extracted from the forest using different neutral solvents, such as acetone. [ 27 ] analogous subject is give in the alleged exudate produced by trees in response to mechanical damage or after being attacked by insects or fungi. [ 28 ] Unlike the structural constituents, the typography of extractives varies over wide ranges and depends on many factors. [ 29 ] The come and constitution of extractives differs between corner species, versatile parts of the same tree, and depends on genic factors and growth conditions, such as climate and geography. [ 27 ] For example, slower growing trees and higher parts of trees have higher content of extractives. by and large, the softwood is richer in extractives than the hardwood. Their concentration increases from the cambium to the kernel. Barks and branches besides contain extractives. Although extractives represent a small fraction of the forest content, normally less than 10 %, they are inordinately divers and therefore characterize the chemistry of the wood species. [ 30 ] Most extractives are secondary metabolites and some of them serve as precursors to early chemicals. Wood extractives display unlike activities, some of them are produced in response to wounds, and some of them participate in natural defense against insects and fungi. [ 31 ]
These compounds contribute to assorted physical and chemical properties of the woodwind, such as wood color, fragnance, lastingness, acoustic properties, hygroscopicity, adhesion, and drying. [ 30 ] Considering these impacts, woodwind extractives besides affect the properties of pulp and wallpaper, and importantly cause many problems in paper industry. Some extractives are surface-active substances and inescapably affect the surface properties of composition, such as water adsorption, friction and military capability. [ 27 ] Lipophilic extractives often give ascent to sticky deposits during kraft pulp and may leave spots on newspaper. Extractives besides account for newspaper smell, which is authoritative when making food contact materials. Most wood extractives are lipophilic and merely a little separate is water-soluble. [ 28 ] The lipophilic dowry of extractives, which is jointly referred as wood resin, contains fats and fatty acids, sterols and steryl esters, terpenes, terpenoids, resin acids, and waxes. [ 32 ] The heat of resin, i.e. distillate, vaporizes the volatile terpenes and leaves the solid part – rosin. The concentrate fluent of volatile compounds extracted during steam distillation is called necessity oil. distillate of oleoresin obtained from many pines provides resin and turpentine. [ 33 ] Most extractives can be categorized into three groups : aliphatic compounds, terpenes and phenolic resin compounds. [ 27 ] The latter are more water-soluble and normally are absent in the resin .
Uses
fuel
forest has a long history of being used as fuel, [ 37 ] which continues to this day, by and large in rural areas of the earth. Hardwood is preferred over softwood because it creates less smoke and burns longer. Adding a woodstove or fireplace to a home is frequently felt to add ambiance and heat .
pulpwood
pulpwood is wood that is raised specifically for use in making paper .
construction
wood has been an important construction material since humans began building shelters, houses and boats. closely all boats were made out of forest until the recently nineteenth hundred, and wood remains in common consumption today in boat construction. Elm in finical was used for this determination as it resisted decay deoxyadenosine monophosphate long as it was kept wet ( it besides served for water pipe before the advent of more modern plumb ). forest to be used for construction sour is normally known as lumber in North America. Elsewhere, lumber normally refers to felled trees, and the bible for saw planks ready for use is timber. [ 39 ] In Medieval Europe oak was the wood of choice for all wood construction, including beams, walls, doors, and floors. nowadays a wider kind of woods is used : solid forest doors are much made from poplar, small-knotted ache, and Douglas fir .
New domestic house in many parts of the global nowadays is normally made from timber-framed construction. Engineered wood products are becoming a bigger part of the construction industry. They may be used in both residential and commercial buildings as morphologic and aesthetic materials. In buildings made of other materials, woodwind will still be found as a supporting material, particularly in roof construction, in home doors and their frames, and as exterior facing. wood is besides normally used as shuttering corporeal to form the mold into which concrete is poured during built concrete construction .
Flooring
wood can be cut into square planks and made into a wood flooring A solid wood deck is a floor lay with planks or battens created from a single objet d’art of forest, normally a hardwood. Since forest is hydroscopic ( it acquires and loses moisture from the ambient conditions around it ) this potential instability effectively limits the length and width of the boards. solid hardwood shock is normally cheaper than engineered timbers and damaged areas can be sanded down and refinished repeatedly, the number of times being limited only by the thickness of wood above the tongue. upstanding hardwood floors were in the first place used for structural purposes, being installed vertical to the wooden support beams of a build ( the joists or bearers ) and solid construction forest is even often used for sports floors ampere well as most traditional woodwind blocks, mosaics and parquetry .
Engineered products
Engineered woodwind products, glued build products “ engineered ” for application-specific operation requirements, are much used in construction and industrial applications. Glued engineered wood products are manufactured by bonding in concert wood strands, veneers, lumber or early forms of wood fiber with glue to form a larger, more efficient complex geomorphologic unit. [ 40 ] These products include glued laminate lumber ( glulam ), forest structural panels ( including plywood, oriented strand control panel and composite panels ), laminated veneer baseball bat ( LVL ) and other morphologic composite log ( SCL ) products, parallel ground log, and I-joists. [ 40 ] approximately 100 million cubic meters of wood was consumed for this determination in 1991. [ 3 ] The trends suggest that particle board and fiber board will overtake plywood. Wood inapplicable for construction in its native shape may be broken down mechanically ( into fibers or chips ) or chemically ( into cellulose ) and used as a raw material for early build materials, such as engineer wood, deoxyadenosine monophosphate well as chipboard, chipboard, and medium-density fiberboard ( MDF ). such forest derivatives are widely used : wood fibers are an authoritative component of most wallpaper, and cellulose is used as a component of some man-made materials. Wood derivatives can be used for kinds of flooring, for example laminate deck .
furniture and utensils
wood has always been used extensively for furniture, such as chairs and beds. It is besides used for cock handles and cutter, such as chopsticks, toothpicks, and other utensils, like the wooden spoon and pencil .
early
foster developments include newfangled lignin glue applications, reclaimable food packaging, rubber bore substitution applications, anti-bacterial medical agents, and high persuasiveness fabrics or composites. [ 41 ] As scientists and engineers further learn and develop raw techniques to extract versatile components from wood, or alternatively to modify woodwind, for exemplar by adding components to wood, new more advance products will appear on the market. Moisture capacity electronic monitor can besides enhance next generation forest protective covering. [ 42 ]
art
wood has long been used as an artistic culture medium. It has been used to make sculptures and carvings for millennium. Examples include the totem poles carved by north american autochthonal people from conifer trunks, frequently western Red Cedar ( Thuja plicata ). other uses of woodwind in the arts include :
- Woodcut printmaking and engraving
- Wood can be a surface to paint on, such as in panel painting
- Many musical instruments are made mostly or entirely of wood
Sports and recreational equipment
many types of sports equipment are made of wood, or were constructed of forest in the past. For model, cricket bats are typically made of white willow. The baseball bats which are legal for manipulation in Major League Baseball are frequently made of ash forest or hickory, and in holocene years have been constructed from maple flush though that forest is slightly more fragile. National Basketball Association courts have been traditionally made out of parquetry. many other types of sports and refreshment equipment, such as skis, ice rink ice hockey sticks, lacrosse sticks and archery bows, were normally made of wood in the past, but have since been replaced with more modern materials such as aluminum, titanium or composite materials such as fiberglass and carbon paper roughage. One noteworthy case of this vogue is the family of golf clubs normally known as the woods, the heads of which were traditionally made of persimmon wood in the early days of the game of golf, but are now generally made of metal or ( specially in the case of drivers ) carbon-fiber composites .
bacterial degradation
little is known about the bacteria that degrade cellulose. symbiotic bacteria in Xylophaga may play a character in the abasement of slump woodwind. Alphaproteobacteria, Flavobacteria, Actinobacteria, Clostridia, and Bacteroidetes have been detected in wood submerged for over a class. [ 43 ]
