topic 1-timber

5/20/2018 Topic 1-Timber

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Timber is another name for wood, whether still standingin the form of trees or felled and turned into boards for

construction. Some people may also refer to it as lumber,or differentiate between unprocessed wood and lumberas cut wood packaged for commercial sale. The timberindustry around the world is huge, providing wood for a

variety of products from paper to particleboard.


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Density The density of is a very important factor affecting the strength ofwood. The densest woods are generally the strongest. The density is alsorelated to the stiffness and hardness e.g both these properties increase as thetimber density increases.

Softwoods Softwoods are generally evergreens (coniferous) with needle-likeleaves. They have the following characteristic features. They grow

relatively quickley and trees softwood trees can be felled after 30 years.They have, generally, poor durability qualities unless treated withpreservatives. They are readily available and comparitively cheap

Hardwoods Hardwoods are generally broad-leaved (deciduous) that lose their leaves atthe end of each growing season. The cell structure of hardwoods is morecomplex than softwoods with thick walled cells called fibres providing the

structural support and thin walled cells called vessels providing themeddium for food condution along the trees. Hardwoods have the followingcharacteristics affecting their use. The grow relatively slowly ,resulting indenser, stronger timbers. These tress take over 100 years to mature. Theyhave, generally, good durability qualities with less need for preservatives.They are obtained from tropical areas and are comparatively expensive.


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Moisture Content Timber has high moisture content when first processed fromthe tree. The moisture content is reduced prior to thetimber being used as a structural material. The drying offtimber can be achieved using either of two methods

1) Air seasoning - The timber is stacked in open sidedweatherprrof containers is such the air can freely circulatedto all surfaces of the timber to promote drying. This processcan take considerable time and much space is required.2) Kiln Drying - The timber is dried out in heated ,ventilated and dehumidified ovens. This process requiresspecial equipment and requires high energy energy use.However the process is controlled and rapid. Because of thenature of timber poor control of the drying process canresult in a range of defects including bowing, cupping,twisting and cracking.

Directional Properties

/ Anisotropy The properties of timber are different in different directions.The elastic modulus and strength of wood is much greater ina direction along the grain than across the grain. If the

grain is sloping at an angle to the direction of loading thiscan also have a marked effect of the strength of the timber.


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Stress/

Strain

relationship

At low stress levels the strain is proportional to thestrain. The strain is greater for a given stress at highmoisture contents. However timber does have significant

creep characteristics i.e over time at high constant stressvalues the strain will increase. In calculating strength ofstructures the duration of the loading is one of the factorsto be considered.

Thermal

Properties

Timber is a poor conductor of heat. The denser timbers are

better conductors than the lighter timbers. Timber expandswhen heated but this is offset by the reduction in sectionresulting from the loss of moisture.

Fire Resistance Timber compares favourably with other constructionmaterials in terms of fire resistance. Small timber section

may ignite easily and reduce to ash. However largersections have significant resistance to fire because thesurfaces initially in contact with the flames burn tocharcoal which resists the further spread of the flame.


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Durability Timber does not corrode. It is however subject to weathering,chemical attack, and fungal attack. The durability of timbervaries depending on the wood species. If timber is kept dry or is

continuously immersed in fresh water then decay shoud not bea problem. Timber immersed in seawater is at high risk ofdamage resulting from attack by molluscs. There are a numberof preservative treatments available to prevent the deteriorationof timber resulting from fungi, insects or molluscs. The types of

wood presevative treatments available are briefly described bel1) Tar oil penetration - Creosote is a a typical tar oilpresevative. This group is used generally for external systemssuch as telegraph poles , fences, railway sleepers, timberenclosures (garden sheds) etc.2) Organic solvents.. These are widely used and are appliedusing simple techniques such a brushing spraying or dipping.3) Water borne solvents are the most widely used for industrialapplications and are normally applied into the timber underpressure.


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Name Botanical Name Treatability

Working Properties

NailingLIGHT HARDWOOD

Melantai Shorea macroptera Difficult Good

Kungkur Pithecellobiumspp. Difficult Poor

KembangSemangkuk Scaphiumspp. Very Easy Good

Medang Spp. of Lauraceae Very Difficult ExcellentMelunak Pentacespp. Very Difficult GoodKedondong Spp. of Burseraceae Very Difficult GoodJelutong Dyera spp. Extremely Easy Excellent

Machang Mangifera spp. Very Easy Excellent

Ramin Gonystylusspp. Extremely Easy Poor

Dark Red Meranti Shoreaspp. Difficult GoodMempisang Spp. of Annonaceae Extremely Easy PoorMeranti Bakau Shorea uliginosa Easy Good

Rubberwood Hevea brasiliensis Easy Good

White Meranti Shoreaspp. Easy Poor


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Nyatoh Spp. of Sapotaceae Very Difficult Good to Excellent

Mersawa Anisopteraspp. Difficult Good

Light Red Meranti Shoreaspp. Difficult Good to Poor

Sepetir Sindoraspp. Moderately Difficult GoodGerutu Parashoreaspp. Very Difficult Excellent

Pulai Alstoniaspp. Extremely Easy Excellent

Yellow Meranti Shoreaspp. Moderately Difficult Poor

Petai Parkiaspp. Extremely Easy Excellent

Geronggang Cratoxylumspp. Extremely Easy Excellent

Durian

Duriospp., Neesiaspp.

Very Easy Good to Excellent

Bintangor Calophyllumspp. Moderately Difficult Poor

Sesendok Endospermumspp. Extremely Easy ExcellentTerap Artocarpusspp. Moderately Difficult Good

Penarahan Spp. of Myristicaceae Very Easy Good

Perupok Lophopetalumspp. Difficult Poor

Terentang Campnospermaspp. Easy Excellent


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SOFTWOOD Conifers)

Damar Minyak Agathis borneensis Extremely Easy Excellent

Podo Podocarpusspp. n.a. -

MEDIUM HARDWOOD

Kulim

Scorodocarpus

borneensisAverage Very Poor

Keruing Dipterocarpusspp. Average Very Poor

Kempas

Koompassia

malaccensis

Easy Poor

Mengkulang Heritieraspp. Average Good

Merpauh Swintoniaspp. Very Easy Good to Very Poor

Meransi Caralliaspp. Average n.a.

Mata Ulat Kokoonaspp. Very Difficult n.a.

Rengas Gluta spp. Very Difficult Excellent

Punah Tetramerista glabra Average Good

Tualang Koompassia excelsa Easy Good

Simpoh Dilleniaspp. Easy Poor


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Kasai Pometiaspp. Very Difficult Good

Kelat Eugeniaspp. Difficult Poor

Keledang Artocarpusspp. Very Difficult Good

Kapur Dryobalanopsspp. Difficult Poor

Merawan Hopeaspp. Difficult Very Poor

HEAVY HARDWOOD

Balau Shoreaspp. Very Difficult Very Poor

Bitis

Madhuca utilis, palaquium

ridleyi & P. StellatumDifficult Very Poor

Chengal Neobalanocarpus heimii Moderately Difficult Very Poor

Giam Hopeaspp. Very Difficult Very Poor

Red Balau Shoreaspp. Very Difficult Poor

Merbau Intsia palembanica Very Difficult Very Poor

Tembusu Fagraeaspp. Very Difficult Good

Resak Vaticaspp. Very Difficult n.a.

Keranji Dialiumspp. Difficult Good

Kekatong Cynometraspp. Very Difficult Poor


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Natural Drying

- With this process the timber roughly sawn to size and stacked using spacers calledstickers, with the timber stacked in the open air.

- Vertical spacing achieved by nusing timber battens (25mm) of the same species. Thepiling sticks should be spaced closed enough to prevent bowing (600mm to 900mmcentres). This allows the free movement of air.

- The stack should be protected from the direct influence of the elements.

- The ends of the beams must be painted to prevent splitting. Advantages

- No expensive equipment needed

- Small labour cost once stack is made

- Environmentally friendlyuses little energy

Disadvantages

- Slow drying rate

- Large area of space required for a lot of timber

- Only dries the timber approximately 20% M.C. so leaving it open to some insect and fugalattacks while it is only suitable for aotdoor joinery.


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Sloping roof to allow rainwater to run off


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Klin drying

- There are two main types of kiln used in artifal seasoning

1) Compartmental Kilns2) Progressive Kilns

- Both methods rely on the controlled environment to dry out the timber andrequire the following factors:

# Forced air circulation by using large fans, blowers, etc

# Heat of some form provided by piped steam.# Humidity control provided by steam jets.

- The amount and duration of air, heat and humidity again depends on species,size, quantity, etc.

- In the general the atmosphere in the klin at first will be cool and moist. The

temperature is gradually increased and the humidity reduced until the requiredmoisture content achieved.


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Advantage

- Quicker due to higher temperatures, ventilation and air circulation

- Achieve a lower moisture content

- Defects associated with drying can be controlled

- Allows more precise rates of drying for various timber species andthickness of boards.

Disadvantage- Is expensive

- Requires supervision by skilled operator

- Uses a lot of energy


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Decay, Rot or Unsound Wood

Decay results from fungal activity. The wood loses its strength and may become soft orpunky. Decay can be seen in a variety of forms. These forms are known as whitespeck,honeycomb,and peck.

Knots

Knots are created where branches grew from the stem of the tree. Size and number of knotswill affect the grade of the lumber. Additionally, the wood of the knot may fall out and leavea hole. This happens when the branch forming the knot dies and the wood is not bonded tothe trunkwood.

Shake

A shake is a lengthwise separation of the wood. Shakes are most likely caused by wind

damage. When the tree tissues are not elastic enough to withstand the stress as the tree isbent by wind, the tissues separate. If the separation is between or along the annual rings, it isknown as a cup shake. If the separations radiate from the heartwood, they are known asheart or star shake. Shakes may also be caused in the drying process.


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Timber Breaks

Timber breaks are tiny cracks that zigzag across the grain of a board or plank. Their cause isunknown but may be due to wind stresses or hard contact with the ground during felling.

Pitch

Pitch is an accumulation of resinous material. This is unsuitable for certain grades of lumberbecause of appearance requirements. Pitch may be present in streaks or pockets.

Sap StainSap stain is a variation in the natural colour of the wood. This is unsuitable for certain grades

of lumber because of appearance requirements. The usefulness of stained wood is reducedto uses where natural finishes will be applied. Stained wood is divided into light, medium,and heavy stained categories. Sap stain will not progress when the wood has been kiln dried

and planed.Heart Stain

The heartwood is naturally a darker colour than the sapwood. However, if the colour is inirregular patches, it is called heart stain. This is often a dark or reddish colour, but mayrange from pink to brown. Heart stain is unsuitable for certain grades of lumber because thestrength can be affected.

Bark Pockets

Pockets of bark may be present in lumber as a result of the stem of the tree growingoutwards around a branch that has broken off. Bark pockets can also occur when scar tissueis formed after an injury.


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Decay, Rot or Unsound Wood

Knots Shake

Timber Breaks

Pitch Sap Stain

Heart Stain Bark Pockets


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Insect Damage

Wood is prone to attack from a fairly wide array of insects.

Pith Fleck Pith fleck are small darkened streaks or flecks on the face of a boardcreated by the larvae of tiny flies.Pinholes: Small round pinholes, up to 3 mm (1/8) in diameter are usually thework of an insect known as the ambrosia beetle. The damage occurs when theadult beetle bores into the wood carrying a tiny fungus spore with it. It depositsthe spore in the wood tissue and as the spore develops it causes deep staining onthe walls of the bore hole.

Wormholes Wormholes are larger than pinholes. Usually they range from 3 mmto 12 mm (1/8to 1/2)in size and they consist of elliptical or circular galleries ortunnels in the wood. Wormholes are caused by the larvae of several insects,including longhorn and flathead wood borers and horntail wasps.


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Reaction Wood

Reaction wood or timber bind develops from a leaning tree stem or trunk.Once the stem of a tree begins to grow in a direction other than vertical, the

force of gravity puts considerable stress on one side of the tree. It is thoughtthat trees produce reaction wood to compensate for this stress. There are twotypes of reaction wood: compression wood in softwoods and tension wood inhardwoods.

Compression Wood

In softwood trees, reaction wood forms on the underside of a leaning stem. It is referredto as compression wood because it is compressed by the weight of the tree stem ortrunk. Compression wood has a hardened, brittle quality that severely reduces itsstrength.

Another major problem with compression wood is its tendency to shrink along its length.Severe warping may result. It has an abnormal tendency to split and is difficult tomachine.


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Processor Marks

A tree is stripped of branches by a processor. If the hydraulic rolls of the processorare improperly aligned, the rolls will leave marks on the log.

Picaroon Holes

These small holes are caused by the use of a lumber handling tool called a picaroon.This tool gouges holes in the lumber.

Dog Holes

Dog holes are large rough holes created by handling the logs by tools known asdogs, tongs, turners, or other such equipment.

Profile Channel or Notch

Some sawmills use a chip-n-saw which cuts a small channel or notch on thebottom of each cant. The channel or notch is supposed to be removed as part of

the operation, but sometimes is not.Wane

Wane arises when a board includes a portion of the trees original surface. As aconsequence, a corner or edge of the board is rounded rather than squared.


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Saw Offset

A board with saw offset has sides that are parallel, but not entirely in the same plane;one section of the board is offset from the rest.

Tearing of Face

Tearing of face consists of parts of the wood being torn out during rough-sawingbelow the line of cut. When planed, this shows as pock marks or smallindentations on the surface of the lumber. This is most common in cedar.

Tearing of Faceaw Offsetanerofile Channel or Notch

Dog Holes

icaroon Holes

Processor Marks


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Cup - Cupping occurs when a board becomes curved across its width. In mostcases, holding boards flat during the drying process may prevent cupping. Boardsnear the bottom of a stack are held flat by the weight of the boards above. The toplayers must be weighted.

Bow - Bow describes a board that curves along its length. In other words, whenthe convex side of a bowed board is laid flat on a level surface, both ends cannotbe made to touch the surface at the same time. Bow usually results from uneven

shrinkage in a given piece of wood. The most common cause is the presence ofreaction wood in a board. Crook - A crook is similar to a bow except that warping or bending occurs along

the edges of a board. As a result, the distorted board resembles the base of arocking chair. Crooks are created in much the same way as bows. The onlydifference is that the abnormal wood is concentrated along one edge rather thanalong one side.

Twist - When a board is laid flat on a level surface and only three corners of thatboard touch the surface, the board is said to have a twist. Minor twisting mayresult from the inclusion of uneven or irregular reaction wood in a board, butpronounced twisting is associated with spiral grain pattern in wood.


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Diamonding - Diamonding occurs when a square or rectangular piece of woodhas shrunk more along one diagonal than along the other. As a result, the boarddistorts to form a roughly diamond shape at the ends. Since wood shrinks twice asmuch along its tangential face as along its radial face, diamonding will resultwhenever the growth rings are oriented diagonally on the transverse surface ofthe piece. Round cross-sections and holes bored length-wise into a log will alsoexhibit distortion by assuming an oval shape after drying.

Case Hardening - Case hardening is a defect caused in the drying of wood,particularly when kiln drying. If the outer layers of the lumber dry before thecore, the outer layers are prevented from shrinking and become tension-set.When the core dries, the tension-set outer layers prevent the core fromshrinking. This condition is called case hardening. If the lumber is to be used asis,the case hardening condition is not serious. However, if the lumber is re-sawn,the stress is released and distortion occurs. The standard way to test for casehardening is to use the tuningfork test. In this procedure, about one third of thetotal board is removed by cutting a deep groove in one edge, so that theremainder looks like the head of a tuning fork. The two prongs will bend inwardin the case of hardened wood. The two prongs will bend outward in the reverse

case of hardened wood.

Collapse- Collapse is a server distortion of cells which occurs in wood during theearly stages of drying. The wood fibers appear to have collapsed inward on thesurface.


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Brush Treatment

Two or more coats should be given, the later coats to be applied before the preceding coats

dry. A large brush should be used and the liquid should be flooded on to the timber in aflowing coat, not brushed out like paint. Penetration of the end grain is most important, andpreferably the timber should be treated while standing in a bucket or tank containing theliquid.

Spraying

The surface of the wood should be flooded with each coat, and two or more coats applied asin brushing. For the treatment of timber generally a very careful adjustment of the sprayingequipment is necessary to obtain satisfactory results. A low pressure and a suitable nozzlemust be used, so as to avoid production of an atomized mist and/or bouncing liquid off thewood surface. Both are wasteful and inefficient, and the former allows excessive drift ontothe operator.

These comments apply equally to spraying of timber in pre-treatment or in Woodwormeradication in which case spraying is usually the only practical method of applying theinsecticide on a large scale.


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Pressure Impregnation(Vac Vac or Double Vac Process)

The double vacuum process is where (using a special pressure tank) a

vacuum is set up within the timber, which is used to draw thepreservative into the timber. Liquid pressure may be applied to increasepenetration and uptake of preservative. At the end of the treatment asecond vacuum is drawn to remove excess preservative from the timber.Compared to other methods of applying organic solvent preservatives

(brush, spray, immersion, hot and cold soak) the pressure processachieves greater penetration and hence better preservation than brush,spray, or short dip, is quicker and utilizes less preservative than prolongedimmersion or hot and cold soak. Treated timber is drier and cleaneressentially drip free when removed from the treating process. The dryingperiod (to painting) is shorter.


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Fumigation

To treat hard to reach timbers in-situ, preservative impregnated smoke canisterscan be used. These distribute smoke throughout the building space and leave a

fine impregnated dust on the surface of timbers which wood destroying insectsmust cross when they emerge from their flight holes. This process is generallyundertaken each year for up to 10 years to ensure the preservative is still toxicwhen the insects emerge.

Dipping

This is, in every way, the most effective of the simple methods of treatment, andshould be employed whenever possible. For building timbers in new houses,dipping for three to ten minutes will be sufficient. When timber is to be used forreplacements in cases of Dry Rot, a longer immersion should be given, up to 10minutes. When wood is to be used in contact with the ground, soaking for one

hour or more is advised. If it is not possible to soak the whole length of the timberthen it should be given a prolonged brush treatment.


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Natural

Timber is one of the few natural building material. This has a lot of advantages.Generally, timber is not toxic, does not leak chemical vapour into the buildingand is safe to handle and touch. It also means that as timber ages, it does sonaturally and doesnt break down into environmentally damaging materials.

Renewable

People have been building with timber for thousands of years. Timber iscontinually being grown in our forests and plantations. As long as new trees areplanted to replace those harvested, timber will continue to be available.

Low in production energy

It takes very little energy to convert the wood in trees to the timber used inbuilding. This means that the embodied energy in timber is very low, the lowest ofalmost all common building materials.


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A store for carbon

Timber is made from carbon drawn from the atmosphere. This carbon wouldotherwise be adding to the greenhouse effect. Using timber in buildings stores thecarbon for as long as the building stands or the timber is used.

A very good insulator

In reducing the amount of energy used to heat and operate a building, insulationis very important. Timber is a natural insulator and can reduce energy needsespecially when it is used in windows, doors and floors.

Readily availableTimber is milled all over Australia and is often used close to where it is produced.This promotes local economies and reduces the energy needed to transportmaterials long distances.

Easy to work

Timber is versatile and can be used in a wide variety of ways. Being light, it is easyto install and can be worked with simple equipment. This reduces the energyneeded for construction.


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Water can be absorbed into the material, causing it to rot andmold

Easy to burn

Using timber frames can lead wildlife extinct

Slight chance of dry rot or wood worm if the timber is nottreated properly in the first place

Noise from footsteps in adjacent rooms above, below, and onthe same floor in such buildings can be quite audible


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Plywood-Plywoodis a manufactured wood panel made from thin sheets of woodveneer. It is one of the most widely used wood products. It is flexible, inexpensive,workable, and re-usable, and usually can be manufactured locally. Plywood isused instead of plain wood because of plywood's resistance to cracking, shrinkage,splitting, and twisting/warping, and because of its generally high strength.


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Uses of plywood

Plywood is manufactured timber made from thin sheets of wood veneer. It ismade by gluing together thin plies of softwood or hardwood. Plywood is used forwall panelling, flooring and making furniture.

Plywood is a special type of timber made from thin layers of wood veneer. It canbe used inside or outside for furniture's, sheds, floor, boat construction,blackboards, billboards, bathroom units, agricultural construction, ceilings,containers or boxes, counter tops, crates, dog kennels, kitchen units, letter boxesamong others. The design used to make plywood makes it more advantageous to

use because of its standard size, strength, stability and low cost. Based on whereone wants to use plywood, it is important to get the right one suitable for the kindof work.

Plywood is a form of wood manufactured using thin sheets of wood. It is used fordomestic construction projects such as shelves, tables, drawers and wallseparators in wooden houses.

Plywood can be used for many different projects. It can be used as sub-flooring,table tops, and even yard decorations.


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Uses of Chipboard

Chip board - Chipboard is cardboard that is not corrugated. It is notparticle board or made of wood chips in any way, instead made of

recycled paper which is pressed into a paperboard. Though it does have agrain like wood, with one direction being more sturdy then the other, it isnot wood. Cereal boxes, tissue boxes, fruit snack boxes, etc are all made ofchipboard. Chipboard comes in two colors, Kraft and News. Kraft isbrown and News is Grey. If you look inside your cereal boxes you cancompare the colors.

Types of Chipboard - White chipboard is clay-coated chipboard. Thecoating is applied to only one side of the board. The other side is eitherKraft or News. Just like a cereal box you can see the white coating firstand then the printer applies the colored ink over the clay-coating for thedesign. There are many thicknesses of chipboard. The higher the number

the thicker the chipboard is. A cereal box thickness is .022. We carryfrom .022 to .080, however, you can find chipboard from .012 to .120+.Some of the thicker chipboard is often referred to as book board, daveyboard, or pasted board


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Uses for chipboard

-Covers for albums - bound or loose

-Die cutting (sizzix, cuttlebug, cricut, etc)

-Scrapbooking - chipboard letters, numbers, titles, etc.-Backing for notebooks or note pads

-Art projects - drawing and painting

-Graphic design projects

-Screen Printing "scraperboards"

-Stiffeners for mailing envelopes

Uses of Particle Board

Particle board is a low-density variety of fiberboard that is made from

scraps of wood like sawdust or bits of wood. You can also find particleboard made from green materials like fibers leftover from the productionof sugarcane.


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These particles are collected, ground and pressed together. A properbinding agent is added and when it is formed particle board is thefinished product. Particle board is inexpensive and versatile making it a

great product for many industries. Particle board can be covered in aveneer so that it can be visible. The following article will share with youthe best uses for particle board.

1. Making Furniture

Any time you buy a dresser or entertainment center you are usuallypurchasing a product made from particle board. This is because particleboard is very inexpensive and easy to work with. Furniture that costsmore can use a variety of fiberboard and natural milled wood. The samelook can be accomplished with basic particle board and severalmainstream furniture companies have had great success using it as theirmain material.


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2. Cabinets

When you set out to have cabinets installed in your home the first thingyou will notice is cost. They are very expensive and forget getting custom

cabinets made because the expensive could smother you. That is if you useall wood and not particle board. The best solution is to use particle boardcases and real wood faces. This creates a fairly inexpensive cabinet andmakes particle board a popular product in the industry.

3. Home Accents

There are many areas of the home that can spruced up by adding accentpieces. The most popular place for accents are around windows, doors,floor and ceiling in the form of trim and molding. These materials aremade cheaper when they are created from particle board. Particle board

is easy to install and even easier to paint


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4. Flooring

Particle board normally is not used as a main flooring but is often used tocover hardwood floors that are already present in a home. The new

particle board floor is then covered with carpet or tile. This is done toprotect the natural hardwood and, if you choose to go back to hardwood,it will not be hard to do

5. Roofing

Particle board comes in several thicknesses which make it a versatileenough product to be used in roofing. Treated lumber is often used as themain material with thin sheets of treated particle board being placed ontop and then shingles are attached. This is especially common on a low-slope roof.


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6. Insulation

Due to the durability of particle board it is sometimes used an addedinsulating material. Other products are used in conjunction with it tokeep heat loss and moisture at a minimum.

7. Sound Deadening

If you dismantle a speaker you'll notice they're made from particle board.This is because the material absorbs sound and does not bounce it back.This is why particle board is use in walls and floors in recording studios,

concert halls and media rooms.

Uses of Particle Board

Medium-density fibreboard (MDF) is an engineered wood productformed by breaking down hardwood or softwood residuals into woodfibres, often in a defibrator, combining it with wax and a resin binder,and forming panels by applying high temperature and pressure. MDF is

generally denser than plywood. It is made up of separated fibres, but canbe used as a building material similar in application to plywood. It isstronger and much denser than particle board.


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MDF was originally developed exclusively for furniture. But it's weightstrength and aesthetics have seen its proliferation to many uses. It is usedextensively in kitchens and for mouldings, and in bathroom

environments. It's use as an exterior cladding for housing has successfullybeen trialed, and structural applications are increasing.

MDF has been able to take over from the traditional materials used(especially particleboard) in the aforementioned applications because:

* It's moderate overall density and suitable density profile give it

excellent machining characteristics* It has greater moisture tolerance than particleboard

* It has very strength, with a Modulus of Elasticity of 2500 MPa forstandard boards to over 5000 MPa for higher density varieties of MDF.Modulus of Rupture is from 28 to 80 MPa depending on thickness and

types.* Aesthetically pleasing.


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There is a trend for furniture to become more ornate ( or a return tofurniture being ornate) and the machinability, the laquering properties,strength and ability to maintain shape will be well suited to MDF. Door

skins and architraves are easily moulded.MDF has better moisture sorption characteristics than timberThe Fire resistance of MDF is also better than that of timberAlthough attractive enough in its raw form MDF is usually coated with aMelamine paper, which can provide a full palette of colours and artificial

wood veneers. True wood veneers, other plastics, paints and aluminiumwill all adhere to MDF. The author was recently impressed by its use, inthe raw form, as stands to set of wood carvings in a forest gallery.

topic 1-timber

Documents

properties of timber

moisture content timber

strength of wood

softwoods softwoods

high moisture content

unprocessed wood

trees softwood trees

drying process canresult