Here is a list of wood products that are mainly obtained from forests.
Product # 1. Lumber/Timber:
Lumber is a general term which includes board, dimension lumber and timber. Thinnest sizes are referred as Boards (thickness ranges from 1″ to 1.5″). Board is used for range of rough or finished products such as packaging, crating, paneling, siding, flooring, moulding. Similar but thicker sizes are referred as Dimension Lumber (thickness ranges from 2″ to 4″).
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It is used for framing and structural applications such as joists, planks, rafters, studs, small posts or beams. Larger sizes are called Timbers (thickness 5″ or more). Lumber is the wood in any of its stages from felling to readiness for use as structural material for construction or wood pulp for paper production. It is supplied either rough or finished. Besides pulpwood, rough lumber is the raw material for furniture-making and other items requiring additional cutting and shaping.
Finished lumber is supplied in standard sizes mostly for the construction industry primarily from softwoods or coniferous species but also from some hardwoods for high-grade flooring. In the United Kingdom and other Commonwealth countries such as India, Australia and New Zealand, timber is a term also used for sawn wood products e.g., timber floor boards, whereas generally in the United States and Canada, the product of timber cut into boards is referred to as lumber.
In the United States and Canada, timber often refers to the wood contents of standing, live trees that can be used for lumber or fibre production. It can also be used to describe sawn lumber whose smallest dimension is not less than 5 inches (127 mm) such as the large dimension and often partially finished lumber used in timber-frame construction. The word lumberjack is used in the UK and Australia to refer to North Americans who fell standing trees and so the word lumber conjures images of what North Americans call timber, and vice versa.
Wood to be used for construction work is commonly known as lumber in North America. Elsewhere, lumber usually refers to felled trees and the word for sawn planks ready for use is timber. Dimensional lumber is a term used for lumber that is finished/planed and cut to standardized width and depth specified in inches.
Examples of common sizes are 2×4, 4×2, 2×6 and 4×4. The length of a board is usually specified separately from the width and depth. It is thus possible to find 2x4s that are four, eight or 12 feet in length. The standard lengths of lumber are 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 feet.
In India, main timber species are Deodar (Cedrus deodara), Sal (Shorea robusta), Teak (Tectona grandis), Babool (Acacia nilotica), Chir pine (Pinus roxbughii), Toon (Toona ciliata), Mahua (Madhuca indica), Neem (Azadirachta indica), Haldu (Adina cordifolia). Silver fir (Abies pindrow), Spruce (Picea smithiana), Irul (Xylia xylocarpa), Chickrassy (Chukrassia tabularis), Calophyllum spp., Gurjan (Dipterocarpus indicus), Artocarpus spp, Terminalia spp., etc. Teak, also called king of timber, is still placed high value in furniture, cabinet and flooring. Among fast growing industrial woods, Eucalyptus, Casuarina, Poplar, Robinia, Ailanthus, Melia, Salix and Morus are common in different ecologies of India.
Product # 2. Composite Wood/Engineered Wood:
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Composite wood or engineered wood is a general term for built up bonded products, consisting either wholly natural wood or in combination of wood fibres, strips, metal, plastic and veneer sheets. Smaller diameter trees of the same hard and softwood used to manufacture lumber are also used. In engineered wood products, the materials are bonded together using an adhesive resin which makes the finished product resist warping.
Some different products made from engineered wood include flooring, several types of lumber and particle board. Engineered flooring is commonly used in both residential and commercial properties because it is typically less expensive and often stronger than traditional hardwood. An engineered hardwood floor is constructed using a thin layer of sealed and sanded hardwood glued to a thicker bottom layer of plywood.
In recent years, various methods and processes have been developed for building larger piece from relatively smaller pieces or treating and modifying wood by means of pressure, heat and chemicals. These processes help in utilizing waste wood and wood of inferior species.
Engineered lumber is broad term used to describe several types of engineered wood products. Engineered wood products are becoming a bigger part of the construction industry. They may be used in both residential and commercial buildings as structural and aesthetic materials. In buildings made of other materials, wood will still be found as a supporting material, especially in roof construction, in interior doors and their frames and as exterior cladding.
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Engineered wood products, glued building products “engineered” for application- specific performance requirements, are often used in construction and industrial applications. Glued engineered wood products are manufactured by bonding together wood strands, veneers, lumber or other forms of wood fibre with glue to form a larger, more efficient composite structural unit.
These products include glued laminated timber (glulam), wood structural panels (including plywood, oriented strand board and composite panels), laminated veneer lumber (LVL) and other structural composite lumber (SCL) products, parallel strand lumber and I-joists. The trends suggest that particle board and fibre board will overtake plywood.
Engineered wood products display highly predictable and reliable performance characteristics and provide enhanced design flexibility on one hand, these products allow the use of smaller pieces and on the other hand, they allow for bigger spans. They may also be selected for specific projects such as public swimming pools or ice rinks where the wood will not deteriorate in the presence of certain chemicals and are less susceptible to the humidity changes commonly found in these environments.
Engineered wood products prove to be more environmentally friendly and, if used appropriately, are often less expensive than building materials such as steel or concrete. These products are extremely resource-efficient because they use more of the available resource with minimal waste. In most cases, engineered wood products are produced using faster growing and often underutilized wood species from managed forests and plantations.
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Wood unsuitable for construction in its native form may be broken down mechanically (into fibres or chips) or chemically (into cellulose) and used as a raw material for other building materials, such as engineered wood, as well as chipboard, hardboard and medium- density fibreboard (MDF).
Such wood derivatives are widely used in many industries viz. wood fibres are an important component of most paper and cellulose is used as a component of some synthetic materials. Wood derivatives can also be used for kinds of flooring e.g. laminate flooring. Major forms of composite wood are plywood, laminated wood, core boards, sandwich board, fibre boards, particle boards, etc.
Types of Engineered Wood:
1. Glued Laminated Timber.
2. Multilaminar Veneer.
3. Veneer-based Wood.
i. Plywood
ii. Glued laminated timber (Glulam)
iii. Laminated Veneer Lumber (LVL)
iv. Stamina wood
4. Particle-based.
i. Waferboard
ii. Particleboard (Chipboard)
5. Fibre based.
i. Fibreboard
ii. Parallel Strand Lumber (PSL) or Oriented Strand Board (OSB)
iii. Laminated Strand Lumber (LSL)
iv. Insulation board
v. Medium-Density Fibreboard (MDF)
vi. Hardboard
6. Wood-plastic composite.
Types of Adhesives Used in Engineered Wood:
i. Urea-Formaldehyde Resins (UF):
Most common, most cheap and not waterproof
ii. Phenol-Formaldehyde Resins (PF):
Yellow/brown, and commonly used for exterior exposure products
iii. Melamine-Formaldehyde Resin (MF):
White, heat and water resistant and often used in exposed surfaces in more costly designs
iv. Methylene Diphenyl Diisocyanate (MDI) or Polyurethane (PU) Resins:
Expensive, generally waterproof and do not contain formaldehyde
Product # 3. Veneers:
In woodworking, veneer refers to thin slices or sheet of wood, usually thinner than 3 mm (1/8 inch) to as low as 0.05 mm, that typically are glued onto core panels (wood, particle board or medium-density fibreboard) to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry. Plywood consists of three or more layers of veneer, each glued with its grain at right angles to adjacent layers for strength.
Veneer beading is a thin layer of decorative edging placed around objects, such as jewelry boxes. Veneer is also a type of manufactured board. Veneer is obtained either by rotary peeling log or by slicing large rectangular blocks of wood known as flitches. In peeling process, veneers come out as unrolled paper roll and length of log is about 2.5- 3.0 m and thickness of veneers is 1.25 mm, 1.50 mm or 2.5 mm.
In slicing, even thinner veneer with thickness 0.6 mm to 1.25 mm are obtained and mainly done for decorative veneers. The appearance of the grain and figure in wood comes from slicing through the growth rings of a tree and depends upon the angle at which the wood is sliced.
Types of Veneers:
There are a few types of veneers available and each serves a purpose:
i. Raw veneer has no backing on it and can be used with either side facing up. It is important to note that the two sides will appear different when a finish has been applied, due to the cell structure of the wood.
ii. Paper backed veneer is that are backed with paper. The advantage is that it is available in large sizes, or sheets, as smaller pieces are joined together prior to adding the backing. This is helpful for users that do not wish to join smaller pieces of raw veneers together. This is also helpful when veneering curves and columns as the veneer is less likely to crack.
iii. Phenolic backed veneer is less common and is used for composite or manmade wood veneers. Due to concern for the natural resource, this is becoming more popular. It too has the advantage of being available in sheets and is also less likely to crack when being used on curves.
iv. Laid up veneer is raw veneer that has been joined together to make larger pieces. The process is time-consuming and requires great care, but is not difficult and requires no expensive tools or machinery.
Patterns of Veneers:
There are a number of patterns (the way the veneers are laid up) common to veneered work.
i. Book Matched:
Where the veneers are opened from the flitch much like the pages of a book.
ii. Slip Matched:
Where the pieces are joined together in the order they come from the flitch and have the same face kept up.
iii. Radial Matched:
Where the veneer is cut into wedge shaped pieces and joined together.
iv. Diamond Matched:
Where the pattern formed is diamond shaped.
Product # 4. Plywood:
Plywood is a manufactured wood panel made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, inexpensive, workable, re-usable and can usually be locally manufactured. Plywood is used instead of plain wood because of its resistance to cracking, shrinkage, splitting and twisting/warping and its general high degree of strength. Plywood layers (called veneers) are glued together with adjacent plies having their grain at right angles to each other.
Cross-graining has several important benefits: it reduces the tendency of wood to split when nailed at the edges, it reduces expansion and shrinkage equating to improved dimensional stability and makes the strength of the panel consistent across both directions.
There are usually an odd number of plies so that the sheet is balanced- this reduces warping. Because of the way plywood is bonded (with grains running against one another and with an odd number of composite parts), it is very hard to bend it perpendicular to the grain direction.
Plywood was invented around 3500 B.C. by the Egyptians, who attached several thinner layers of wood together to make one thick layer. They originally did this during a shortage of quality wood, gluing very thin layers of quality wood over lesser- quality wood. Modern plywood was invented by Immanuel Nobel, father of Alfred Nobel. Nobel realized that several thinner layers of wood bonded together would be stronger than one single thick layer of wood.
Structural Characteristics:
A typical plywood panel has higher grade face veneers than core veneers. The principal function of the core layers is to increase the separation between the outer layers where the bending stresses are highest, thus increasing the panel’s resistance to bending. As a result, thicker panels can span greater distances under the same loads.
In bending, the maximum stress occurs in the outer layers, one in tension and the other in compression. Bending stress decreases from the maximum at the face layers to nearly zero at the central layer. Shear stress is consistent throughout the depth of the panel.
Plywood production requires a good log, called a peeler, which is generally straighter and larger in diameter than one required for processing into dimensioned lumber by a sawmill. The log is laid horizontally and rotated about its long axis while a long blade is pressed into it, causing a thin layer of wood to peel off.
In this way the log is peeled into sheets of veneer which are then cut to the desired dimensions, dried, patched, glued together and then baked in a press at 140°C (284°F) and 1.9 MPa (280 psi) to form the plywood panel. The panel can then be patched, re-sized, sanded or otherwise refinished, depending on the market for which it is intended.
Plywood for indoor use generally uses the less expensive urea-formaldehyde glue which has limited water resistance, while outdoor and marine-grade plywood are designed to withstand rot and use a water resistant phenol-formaldehyde glue to prevent delamination and to retain strength in high humidity. The adhesives used in plywood have become a point of concern.
Both urea formaldehyde and phenol formaldehyde are carcinogenic in very high concentrations. As a result, many manufacturers are turning to low formaldehyde-emitting glue systems denoted by an “E” rating. Plywood produced to “EO” has effectively zero formaldehyde emissions.
In addition to the glues being brought to the forefront, the wood resources themselves are becoming the focus of manufacturers, due in part to energy conservation, as well as concern for natural resources. Forest Stewardship Council (FSC), Leadership in Energy and Environmental Design (LEED), Sustainable Forestry Initiative (SFI) and Green guard are all certification programs that ensure that production and construction practices are sustainable.
Plywood is used in many applications that need high-quality, high-strength sheet material. Quality in this context means resistance to cracking, breaking, shrinkage, twisting and warping. Exterior glued plywood is suitable for outdoor use, but because moisture affects the strength of wood, optimal performance is achieved in end uses where the wood’s moisture content remains relatively low.
On the other hand, subzero conditions don’t affect plywood’s dimensional or strength properties, which makes some special applications possible. Plywood is also used as an engineering material for stressed-skin applications. Plywood-based furniture and designing a wide range of boats built primarily of plywood are famous in major wood consuming nations. Plywood is often used to create curved surfaces because it can easily bend with the grain. Skateboard ramps often utilize plywood as the top smooth surface over bent curves to create transition that can simulate the shapes of ocean waves.
Product # 5. Improved Wood/ Modified Wood:
The wood is treated in various ways to improve its strength, dimensional stability (hygroscopicity) and service life. It includes impregnation with synthetic resins or other materials and /or compression and / or heating and may be applied to solid wood or the veneers that are subsequently bonded together.
Depending upon treatment, improved woods are categorized as follows:
i. Impregnated Wood:
Wood impregnated by wax, paraffin, resins, oils, etc. with the objective of improving dimensional stability and service life.
ii. Heat Stabilized Wood:
Stabilization of dimension and decay resistance by simple heat treatment (260-315°C for few minutes under non-oxidizing condition) to reduce hygroscopicity.
iii. Compressed Wood:
Wood is compressed to increase the specific gravity of wood at pressure of 90-140 kg/sq. cm without any impregnation.
iv. Compregnated Wood:
Wood is both compressed and impregnated with synthetic resins.
v. Heat Stabilized Compressed Wood:
Wood compressed with heat but without impregnation.
vi. Chemically Modified Wood:
Use of chemicals for impregnation for different resistance e.g., fire, termite, water, etc.
Product # 6. Fuel-Wood:
According to EEA report, Global Energy Demand is nearly 467 exajoules (EJ) and 88 per cent of which is met by fossil fuels. With continuing population growth, global energy demand is expected to grow an additional 50 per cent by 2030 mostly in rapidly industrializing countries. Many countries are developing renewable energy resources (bioenergy) to offset fossil fuel use.
Bioenergy can be obtained from the following:
i. Biofuel:
It is defined as any fuel produced directly or indirectly from biomass e.g. liquid fuels such as ethanol and biodiesel.
ii. Wood-Fuel:
It encompasses all types of biofuel derived directly or indirectly from trees and shrubs (woody biomass) grown on forest and non-forest land.
iii. Fuel-Wood:
It is used to describe woodfuel where the original composition of the wood is preserved.
Fuel-wood is a type of fuel in the form of wood derived from trees and shrubs grown on forest and non-forest land. Firewood remains the dominant source of both domestic and commercial energy requirements for Africa’s rural population.
Substantial increase in human and bovine population as well as decreasing forest areas have led to fuel-wood shortages in many countries. In most African countries and some Asian countries, indigenous woodlands still provide both urban and rural populations with by far the greatest proportion for their fuel-wood requirements.
Fuel wood is a wood used as fuel and the burning of wood is currently the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating and occasionally for fueling steam engines and steam turbines that generate electricity. Wood fuel may be available as firewood, charcoal, chips, sheets, pellets and sawdust.
The particular form used depends upon factors such as source, quantity, quality and application. Sawmill waste and construction industry by-products also include various forms of lumber tailings. Some consider wood fuel bad for the environment; however this is not the case if proper techniques are used.
One might increase carbon emissions using gas powered saws and splitters in the production of firewood, but when wood heat replaces carbon-producing fuels such as propane, heating oil or electricity from a coal-burning plant, then wood burning has a positive impact on the carbon footprint. Wood may be used indoors in a furnace, stove or fireplace. Wood also may be burned outdoors in a campfire or bonfire.
In India and other developing countries fuel-wood is major wood product utilized by the masses to meet out their routine energy needs. The fuelwood demand is about 275 million m3 while supply is only 50 million m3 and forest is still a major source besides agroforestry plantations. Characteristics of ideal fuel-wood tree are: fast growing, multipurpose, good coppicing and pollarding, nitrogen fixing, high calorific value of wood, good combustibility with less smoke, easy to split (fissility).
But most of the woods are used irrespective of these attributes. The major woods used as fuelwood include Acacia spp, Eucalyptus spp, Tamrindus indica, Oak (Quereus spp.) Chirpine (Pinus roxbughii), Neem (Azadirchta indica), Mango (Mangifera indica), Axlewood (Anogeissus pendula), Subabul (Leucaena leucocephala), Anjan (Hardwikia binnata), Palas (Butea monosperma), Albizia spp, Mahua (Madhuca indica), Jamun (Syzygium cumini), Gliricidia spp., Casurina equisetifoila, Prosopis juliflora, Khejri (Prosopis cineraria), Pilu (Salvadora persica), Maharukh (Ailanthus excelsa), Persian liliac (Melia azedarach), Celtis australis, Alnus nepalensis, Ash (Fraxinus micrantha), Black Locust (Robinia pseudocasia), Salix spp., Lyonia spp., etc.
Product # 7. Pulp and Paper Wood:
Origin of paper making can be traced back to China using vegetable wastes but using wood to make paper is a fairly recent innovation. In India, first paper industry was established in 1830 in West Bengal. In the 1800s, fibre crops such as linen fibres were the primary material source and paper was a relatively expensive commodity. The use of wood to make pulp for paper began with the development of mechanical pulping in Germany by F.G. Keller in the 1840s and by the Canadian inventor Charles Fenerty in Nova Scotia.
Chemical processes quickly followed, first with J. Roth’s use of sulfurous acid to treat wood, followed by B. Tilghman’s U.S. patent on the use of calcium bisulfite, Ca(HSO3)2, to pulp wood in 1867. Almost a decade later the first commercial sulphite pulp mill was built in Sweden as a process developed by Carl Daniel Ekman. By 1900, sulphite pulping had become the dominant means of producing wood pulp, surpassing mechanical pulping methods.
The competing chemical pulping process, the sulfate or kraft process was developed by Carl F. Dahl in 1879 and the first kraft mill started (in Sweden) in 1890. The invention of the recovery boiler by G.H. Tomlinson in the early 1930s allowed kraft mills to recycle almost all of their pulping chemicals. This along with the ability of the kraft process to accept a wider variety of types of wood and produce stronger fibres made the kraft process the dominant pulping process starting in the 1940s.
Product # 8. Charcoal:
Charcoal is a formless mass of carbon and can be made from most carbonaceous materials. It is one of the oldest man-made fuels. Charcoal is prepared by firing wood in the absence of air in pyrolysis drum and the product is quenched, collected and packed in gunny bag. Charcoal is inexpensive compared to petroleum fuels (kerosene, LPG, natural gas) and electricity. Charcoal making is termed wasteful because only 30-40 per cent of the wood is actually converted to charcoal. The rest is released into the atmosphere as gases.
Commercially grown trees can produce 18 tons of charcoal from one hectare. Charcoal is a traditional fuel as like fuel-wood and it can be purchased in preferred quantity. It burns without smoke. It does not decompose even after extended storage and does not create dangerous flames around cooking vessels. It requires a simple stove whose heat output is relatively easy to control.
Charcoal Manufacture Techniques:
There are many techniques for making charcoal. In the simplest method, wood is burned in an open fire and the charred remains recovered as charcoal. A more controlled process is by restricting the supply of air during carbonization.
Three main methods are traditionally used:
i. Wood is slacked on the ground and covered with soil, forming what is often referred to as an earth mound kiln.
ii. Second method involves digging a hole in the ground into which the wood is placed and then covered with soil. This one is commonly referred to as a pit-kiln.
iii. Charcoal is also produced by heating wood in airtight ovens or retorts or pyrolysis drums or chambers or in kilns supplied with limited and controlled amounts of air. High-temperature heating by all methods breaks down the wood into gases, a watery tar mixture and the familiar solid carbon material commonly known as charcoal.
Uses of Charcoal:
Charcoal is still a major source of energy throughout the world. Charcoal plays a considerable role in African economies and countries in Asia. Nearly 80 per cent of the African population and majority of Asian rural population continue to depend on traditional biomass fuels (fuel-wood and charcoal) for their energy need. Charcoal industry provides a considerable amount of employment in rural areas.
The major uses of charcoal are:
i. Charcoal is used as fuel for cooking purposes.
ii. It is used in certain metallurgical purifying treatments and as filter to remove organic compounds such as chlorine, gasoline, pesticides and other toxic chemicals from water and air.
iii. Activated charcoal is used in purifying and refining metals.
iv. Activated Charcoal is used in Gas masks that are used during war.
v. Activated charcoal is used as an antidote for many types of poisons and it is an effective anti-flatulent.
Tree Species for Charcoal Production:
i. Prosopis juliflora
ii. Acacia spp.
iii. Eucalyptus spp.
iv. Leucaena leucocephala
v. Casuarina equisetifolia
vi. Sesbania sesban
vii. Albizia spp.
viii. Pterocarpus spp.
ix. Terminalia spp.
x. Tamarindus indica.