Medium Density Fibre

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Jyothi Anna John

S8 Barch

Roll no: 17

Medium Density Fibre


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MediumMedium--densitydensity fibreboardfibreboard ((MDFMDF) is an engineered wood product formed by breaking down) is an engineered wood product formed by breaking downhardwood or softwood residuals into wood fibers, often in ahardwood or softwood residuals into wood fibers, often in a defibratordefibrator combining it with wax and acombining it with wax and aresin binder, and forming panels by applying high temperature and pressure. MDF is more denseresin binder, and forming panels by applying high temperature and pressure. MDF is more densethan plywood.than plywood.

It is made up of separated fibers, (not wood veneers) but can be used as a building material similarIt is made up of separated fibers, (not wood veneers) but can be used as a building material similarin application to plywood. It is stronger and much more dense than normal particle board.in application to plywood. It is stronger and much more dense than normal particle board.

yy The name derives from the distinction in densities of fiberboard. LargeThe name derives from the distinction in densities of fiberboard. Large--scale production of MDFscale production of MDFbegan in the 1980sbegan in the 1980s


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Comparison to natural woods

MDF does not contain knots or rings, making it more uniform than natural woodsduring cutting and in service.MDF is not entirely isotropic like metal, since the fibers are pressed together primarily through the sheet.

Like natural wood, MDF may split when woodscrews are installed without pilot holes.

MDF may be glued, doweled or laminated, but smooth-shank nails do not hold well.

Typical fasteners are T-nuts and pan-head machine screws


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Properties

y Medium Density Fibre board (MDF) is a wood substitute form which is made from fine woodfibres in a resin which is bonded under heat and pressure.

y It is manufactured by a dry process at a lower temperature than other fibre boards e. ghardboard.

y The natural glues and resins contained within the wood are not effective. MDF therefore

uses artificial bonding agents / resins.y The resin used is usually urea formaldehyde, but some fibre board including exterior or

marine quality board will use stronger glues such as phenol formaldehyde.

y MDF may be used instead of plywood or chipboard.

y It is dense, flat, stiff, has no knots and is easily machined.

y It is made up of fine particles and therefore does not have an easily recognisable surface

grain.Can be obtained in natural colour in various thicknesses or self coloured. Requires sealingif likely hood of moisture ingress.


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VARIOUS APPLICATION


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Below are some metrics for MDF and other types of wood. Ex: Weight of MDF board. As you can see, MDF

is very dense and heavy, but is not as stiff as other types of wood which is why bracing is suggested.

The modulus of elasticity (MOE), also called Young's modulus, is the ratio of s tress to strain, where stress is the

force per unit area placed on the item and strain is the deformation caused by the stress. The MOE is therefore a

measure of s tiffness.

WOOD Modulus of

Elasticity (inmillion

pounds per

square inch)

Density

(in pounds percubic feet)

weight of 4x8

sheet(in pounds)

MDF 0.53 48 75-85

OAK 1.55 38 60-70

PINE 1.3 29 45-50

PLYWOOD 1.2 33 45-55


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y Medium Density Fiberboard typically has densities between 33 and 50 pounds per cubic feet whileHigh Density Fiberboard (HDF) ranges between 50 and 80 pounds per cubic feet.

y Physical and dimensional tolerances for MDF are specified in ANSI A208.2-1986

y Its fine particles provide dimensional stability without a predominant "grain" .Unlike most plywoods,MDF contains no voids,

y It will deliver sharp edges with no tearout. MDF is very well damped acoustically thus making it anideal material for speaker enclosures.

Notice the difference


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MDF IS USED SOUND BOXES AND FURNITURES AND

IS AVAILABLE IN DIFFERENT TEXTURES


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CUTTING OF MDF

y MDF can be treated much like a fine grained hardwood. Its high glue content means that steelcutting tools will dull VERY quickly; thus the use of carbide tools is highly recommended.

y For general shop or table saw use with decent cut and good blade life, a 50 tooth, 10 inchcombination blade may be used.

y For those demanding a better cut, consider a 60 tooth, 10 inch blade with alternate top bevel (ATB)

teeth at 15 degrees, 10 degree positive hook, 5 degree side clearance, 10 degree outside diameterclearance, and low approach angle (blade projecting no more than 0.5 inch through top of material).

y For an even smoother cut, consider an 80 tooth, 10 inch blade with 15 degree ATB, 10 degreealternate face bevel, 15 degree positive hook, and 7 degrees side clearance. This is costlier and may

result in a shorter blade life.


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HOW MDF IS SOLD??

MDF from different sources will vary in texture, density, color etc.

MDF is manufactured in sheets up to 8ft x 25ft. Typical consumer level sheets are 4x8 or 5x8 and 1/2

inch, 3/4 inch and 1 inch in thickness.

MDF is also available with a variety of veneers and laminates pre-applied, which may affect its actualthickness.


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MDO, particle board, hardboard, void-free plywood?

y Medium Density Overlay and High Density Overlay are plywood products with a resin impregnated paper coating.They are often used for exterior painted surfaces. These are not fiber based products.

y Likewise, particle board is not fiber based; it is a so lid wood composite product. Along with flakeboard and otherengineered lumbers, composite products are made from wood flakes, chips, splinters, etc., formed into layers andheld together by resin glues and heated under pressure. Being layered and consisting of larger chunks, particleboard does not have the uniform texture of MDF. \

y While MDF is a hardboard, the term hardboard is often used to refer to 1/8 or 1/4 inch thick HDF, usuallycontaining a screen pattern on one s urface.This is commonly referred to as Masonite.

y Plywood is made from an odd number of lumber plies, each layer having a grain direction at right angles to theprevious layer. This arrangement provides a dimensionally stable product. Void-free plywood uses plies withsupposedly no holes, thus the completed plywood has in theory no voids.

y Baltic birch plywood is often sold as void-free plywood though some users have encountered small voids in theseproducts


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USE OFMDF IN A FLEXIBLE WAYTEXURING ON THE WALLS


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JOINTS of MDF

y butt - this simplest of joints may not be ideal for furniture but works very well for building

speakers, especially when combined with biscuits (for alignment) and screws (for holding

strength while the glue dries).

y miter - works well when using pre-finished MDF (veneered or laminated) thus leaving no

exposed unfinished surfaces. lock-miter, dovetail and other routered joints .

y These joints have limited use in most speaker enclosures. rabbets, dadoes, grooves and

other saw cut joints - same as with hardwood.


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What are the safety issues to consider when working with MDF?y

MDF is typically made with urea-formaldehyde resin totaling 9% by weight. While most people will not beaffected by this, people sensitive to formaldehyde emissions should consider low formaldehyde orformaldehyde-free MDF, or consider methods of controlling these emissions through proper finishing.

y Finishes that work best at controlling formaldehyde emissions are solid add-on surfaces such as highpressure laminates, vinyl covering, and finished wood veneers. Less effective at controlling emissionsare simple seal coats, oil and latex paints, danish oil, and wax.

y Plum Creek makes low-formaldehyde MDF, while Medite II and Medex from Medite Corp. are

formaldehyde-free MDF.y Dust is another MDF hazard. The large amount of dust released when working MDF makes proper

respiratory and eye protection mandatory. At a minimum use a dust mask. A respirator is preferable.

y Shop dust collection (or even a ShopVac) would greatly help the removal of dust from not only the air butalso the working surfaces, making them easier to see. Goggles should always be worn while using tools.


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glues to be used with MDF

Good glues to use are gap-filling glues such as polyvinyl acetate (PVA) typically

known as yellow glue, modified PVA glues like Titebond II or white glues. Epoxy, ureaand hot melt glues may also be used.

fasteners be used with MDF

Some typical fasteners and their uses follow :

y staples - Do not staple within 3/4 inch of any corner. Coated staples hold better

than smooth staples. Use a finer wire staple if splitting is a problem. Drive at rightangle to the surface to avoid bending.

y nails - The same rules apply to nails as they apply to staples. Use ring-shank nailsto avoid fiber raising around the nail head; do not use smooth nails.

y screws - Drill pilot holes between 85 % and 90 % of the root diameter of the

screw used and at least as deep as the screw


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Positives

Formaldehyde resins are commonly used to bind MDF together, and testing has

consistently revealed that MDF products emit urea-formaldehyde and other volatile organic

compounds that pose health risks at sufficient concentrations, for at least several months

after manufacture. When painting it is good idea to coat the whole of the product in order to seal in the urea-formaldehyde.

When MDF is cut a large quantity of dust particles are released into the air. It is important

that a respirator be worn and the material be cut in a controlled and ventilated environment.

Negatives

It is strong, but also easy to work and is light weight. One of the most popular uses for medium density fiberboard is affordable furniture.

fiberboard cabinets are actually more affordable and environmentally friendly,making this a popular cabinet choice.

Its a popular art material on which paintings can be done and holes can be dug into it andsculptures can be made


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T h a n k y o u

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Medium Density Fibre