Smoke Chemistry and Chemical Composition
Wood is a source of a wide variety of chemical products. In theory, at least, the number and kind of possible chemical products are equal to those of the products made from petroleum. In practice, however, the chemical products of wood fall into two general groups: products of the chemical processing of wood or its components and wood extractives and their derivatives. Chemical Composition of Wood Wood is essentially composed of cellulose, hemicelluloses, lignin, and extractives. Table 1 presents major chemical compositions of some wood species. Each of these components contributes to fiber properties, which ultimately impact product properties. Table 1. Chemical Composition of Some Wood Species1.
Wood preservative products are those that control wood degradation problems due to fungal rot or decay, sapstain, molds, or wood-destroying insects. Both the treatment process and the use of treatedproducts can result in risks to human health and the environment. Treated wood is most commonly used outdoors. InEPA determined that chromated arsenicals, creosote, and pentachlorophenol could remain in use as long as certain mitigation measures identified in the Reregistration Eligibility Decision Documents REDs were implemented.
What is pure vanilla extract measures included engineering controls such as ventilation and automatic doors for locking and unlocking treatment cylinders. InEPA completed its draft risk assessments for chromated arsenicals, creosote, and pentachlorophenol as a part of its registration review. In each case, EPA found that although the measures required by the REDs reduced worker exposure, these products continued to pose health risks of concern to the workers who apply them.
Creosote and chromated arsenicals were also found to pose risks to the environment. InEPA issued proposed interim decisions for chromated arsenicals, creosote, and pentachlorophenol to address the human health and environmental risks of using these chemicals. For creosote and chromated arsenicals, EPA proposed additional mitigation measures to protect the health of workers in wood treatment facilities.
Next, EPA will issue interim decisions finalizing the measures put forward in the proposed interim decision. Wood preservatives containing chromated arsenicals include preservatives containing chromium, copper and arsenic. Since the s, wood has been pressure treated with chromated arsenicals to protect wood from rotting due to insect and microbial agent attack and wood-boring marine invertebrates. From the s to the early s, the majority of the wood used in outdoor residential settings was chromated arsenical-treated wood.
EPA has classified chromated arsenicals as restricted use products, for use only by certified pesticide applicators. It can be used to produce commercial wood poles, posts, shakes, shingles, permanent foundation support beams, pilings, and other wood products permitted by approved labeling. Read more about CCA. Creosote has been used since as a heavy duty wood preservative. Creosote is obtained from high temperature distillation of coal tar. Pesticide products containing creosote as the active ingredient are used to protect wood against termites, fungi, mites and other pests that can degrade or threaten the integrity of wood products.
Currently, creosote is used for commercial purposes only; it has no registered residential uses. Creosote is a restricted use pesticide that can be used in how to plant a tree in a planter settings such as in railroad ties and utility poles.
Indoor applications of creosote are prohibited as well as application to wood intended for use in interiors or for use in contact with food, feed, or drinking water. Read more about creosote. Pentachlorophenol PCP was registered as a pesticide on December 1, PCP was one of the most widely used biocides in the United States before when pentachlorophenol uses as an herbicide, defoliant, mossicide and disinfectant were removed from product labels.
Currently, there are no registered residential uses. PCP is a restricted use pesticide that is used for commercial purposes, mainly for treating utility poles. Only pressure and thermal treatments of PCP are allowed. Read more about PCP. Propiconazole is a triazole fungicide that was first registered in Propiconazole has been approved by EPA for preserving wood used in millwork, shingles and shakes, siding, plywood, structural lumber and timbers and composites that are used in above ground applications only.
Propiconazole by itself does not protect wood against insect damage. Propiconazole has been approved for surface application or pressure treatment of siding, plywood, millwork, shingles and shakes and above-ground structural lumber and timbers. Triadimefon is a triazole fungicide that was first registered as a wood preservative in Triadimefon was approved by EPA for preserving wood-based composite products and wood products intended for above ground and in ground contact such as wood decking, patio furniture, millwork, guardrails, utility poles, foundation pilings, and fences.
ACC is a wood preservative that is only registered for industrial and commercial uses. The compound will be reevaluated under the Chromated Arsenicals registration review case. The most common of these is DCOIT 3 2H -isothiazolone, 4,5-dichlorooctylwhich was first registered in as a wood preservative for use via pressure treatment, for sapstain protection, and in millwork applications. Init was also approved for use in utility poles. OIT 2-n-octylisothiazolinoneanother isothiazolone, is used as a sapstain wood preservative.
Finally, a mixture of the isothiazolones MIT 2-methylisothiazolineone and CMIT 5-chloromethylisothiazolineone is used in pressure treatment of wood.
More recently, EPA has registered several new wood preservative active ingredients. These wood preservatives have lower toxicity profiles when compared to older wood preservatives. The following chemical wood preservatives are registered for treatment of lumber to be used in the residential lumber and timber market:.
Of these chemicals, ACQ currently is the most widely used wood preservative for residential applications. ACQ alkaline copper quaternary is a water-based wood preservative that prevents decay from fungi and insects i.
It also has relatively low risks, based on its components of copper oxide and quaternary ammonium compounds. Water-based preservatives like ACQ leave a dry, paintable surface. ACQ is registered for use on: lumber, timbers, landscape ties, fence posts, building and utility poles, land, freshwater and marine pilings, sea walls, decking, wood shingles, and other wood structures. Disodium octaborate tetrahydrate DOT is specially formulated for use as a water-based wood preservative and is registered by EPA as well as government agencies throughout Asia, North America and Europe.
Typical applications include: furnishings and interior construction, such as framing, sheathing, sill plates, furring strips, trusses, and joists.
Copper azole is a water-based wood preservative that prevents fungal decay and insect attack; it is a fungicide and insecticide. It is widely used throughout the United States and Canada. Water-based preservatives like copper azole leave wood with a clean, paintable surface after they dry.
Copper azole is registered for treatment of millwork, shingles and shakes, siding, plywood, structural lumber, fence posts, building and utility poles, land and freshwater piling, composites, and other wood products that are used in above-ground, ground contact and fresh water as well as in salt water splash marine decking applications.
Copper napthenate was first registered in and is used to brush, dip, spray, and pressure treat wood that will be used in ground contact, water contact, and above ground such as utility poles, docks, posts, piers, fences, and landscape timbers. Copper napthenate is effective in protecting wood against insect damage.
Copper — HDO was first registered in and is used to pressure-treat wood that will be used as decking, rails, spindles, framing, sill plates, gazebos, fencing, and posts. It is restricted from use in aquatic areas, construction of beehives, or any application associated with how to weld aluminum tubing packaging of food or feed. Polymeric betaine was first registered as an active ingredient in the United States in It is a borate ester that, when applied to wood, breaks down to DDAC didecyl dimethyl ammonium chloride and boric acid.
Polymeric betaine is applied by pressure treatment to forest products. Many of the documents about these pesticides, such as registration review workplans or REDs are available in the Chemical Search database. Contact Us to ask a question, provide feedback, or report a problem. Jump to main content. An official website of the United States government. Contact Us. Overview of Wood How to get more virtual memory on my computer Chemicals Wood preservative products are those that control wood degradation problems due to fungal rot or decay, sapstain, molds, or wood-destroying insects.
Generally, freshly cut logs or lumber are treated and then manufactured into products such as: Seasoned building materials. Utility poles, fence posts and rails. Structural members. Structures and dwellings. Transportation vehicles truck beds and support structures. Crop containers. Lawn furniture and decks. Playground equipment. Log homes. On This Page.
Aug 04, · Although the chemical composition of wood varies from species to species, wood is primarily composed of carbon, hydrogen, oxygen, calcium, potassium, sulfur, nitrogen and magnesium. Most wood contains some amount of water as well. Wood is a fibrous and porous material composed of cellulose fibers. There are currently around 1 trillion tons of wood on Earth and the rate . Sep 24, · Why is wood chemically preserved? There are basically two things that can happen to wood: either it burns or it rots. became popular. The CCA treatment is made of copper, chrome, and arsenate, and it was a very effective product. In fact, it’s still used today for some industrial and agricultural uses, including pole-barn material. In the. Chemical composition of wood: Chemically composed of: 50% carbon · 6% hydrogen · 1% nitrogen · 1% other elements (calcium, potassium, sodium etc.) This is because wood is composed of Cellulose which is composed of straight-chain, insoluble polysaccharide that is composed of glucose molecules linked by beta-1,4 glycosidic bonds. Which helps give the wood strength.
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material — a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression.
Wood is sometimes defined as only the secondary xylem in the stems of trees,  or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. It also conveys water and nutrients between the leaves , other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.
Wood has been used for thousands of years for fuel , as a construction material , for making tools and weapons , furniture and paper. More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.
In approximately 3. Dominant uses were for furniture and building construction. A discovery in the Canadian province of New Brunswick yielded the earliest known plants to have grown wood, approximately to million years ago. Wood can be dated by carbon dating 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 paper. Known constructions using wood date back ten thousand years. Buildings like the European Neolithic long house were made primarily of wood.
Recent use of wood has been enhanced by the addition of steel and bronze into construction. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at the time a tree was cut. Wood, in the strict sense, 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 stem, living branches, and roots.
This process is known as secondary growth ; it is the result of cell 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 mainly of cellulose , hemicellulose and lignin. Where the differences between the four seasons are distinct, e.
New Zealand , growth can occur in a discrete annual or seasonal pattern, leading to growth rings ; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If the distinctiveness between seasons is annual as is the case in equatorial regions, e. Singapore , these growth rings are referred to as annual rings. Where there is little seasonal difference growth rings are likely to be indistinct or absent.
If the bark of the tree has been removed in a particular area, the rings will likely be deformed as the plant overgrows the scar.
If there are differences within a growth 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 usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood.
If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later 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 year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings.
In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate.
Some trees, such as southern oaks , maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.
As a tree grows, lower branches often die, and their bases may become overgrown and enclosed by subsequent layers of trunk wood, forming a type of imperfection known as a knot. The dead branch may not be attached to the trunk wood except at its base, and can drop out after the tree has been sawn into boards.
Knots affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along the wood grain, [ citation needed ] but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" usually darker piece of wood around which the grain of the rest of the wood "flows" parts and rejoins.
Within a knot, the direction of the wood grain direction is up to 90 degrees different from the grain direction of the regular wood. In the tree a knot is either the base of a side branch or a dormant bud.
A knot when the base of a side branch is conical in shape hence the roughly circular cross-section with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.
In grading lumber and structural timber , knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow. 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 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. 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 sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.
In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted , such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution knotting , correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.
Heartwood or duramen  is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation is a genetically programmed process that occurs spontaneously.
Some uncertainty exists as to whether the wood dies during heartwood formation, as it can still chemically react to decay organisms, but only once. The term heartwood derives solely 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 completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live 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 , hackberry , beech , and pine, thick sapwood is the rule.
Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion.
Sapwood or alburnum  is the younger, outermost wood; in the growing tree it is living wood,  and its principal 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 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 first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees of species that do form heartwood grown in the open may become of considerable size, 30 cm 12 in or more in diameter, before any heartwood begins to form, for example, in second-growth hickory , or open-grown pines.
No definite relation exists between the annual rings of growth 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 narrow, more of them are required than where they are wide.
As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is relatively thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less. When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off.
Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old 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 timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.
Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life 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 large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness , strength , and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true. In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous see section of yew log above.
This is produced by deposits in the heartwood of chemical substances, so that a dramatic color variation does not imply a significant difference in the mechanical properties of heartwood and sapwood, although there may be a marked biochemical difference between the two. Some experiments on very resinous longleaf pine specimens indicate an increase in strength, due to the resin which increases the strength when dry.
Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites ; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.