Medium Density Fibreboard (MDF)

Medium Density Fibreboard is an interior-use engineered wood panel product, manufactured from wood fibres.

Overview

Medium Density Fibreboard (MDF) is a reconstituted wood panel product. It is a dry-processed fibreboard manufactured from wood fibres, as opposed to veneers or particles, and is denser than plywood and particleboard. MDF has an even density throughout and is smooth on both sides.

MDF is reconstituted into wood sheets in a variety of widths and lengths. Bonding is achieved by the addition of synthetic resin adhesives, which are cured under heat and pressure. Paraffin wax is added to assist with water repellency, while other chemicals can be added during manufacturing for more specific protection.

MDF is primarily used for internal use applications, in part due to its poor moisture resistance. It is available in raw form with a fine sanded surface or with decorative overlay such as wood veneer, melamine paper or vinyl.

Note: Other general purpose dry-processed fibreboards are available, being Ultra Low Density, Low Density, High Density (HDF) and High Performance (MR only). These tend to be specialty products, so further information about their usage should be confirmed directly with the manufacturer.

Properties

Durability

While it is unlikely in cooler environments, MDF is still susceptible to attack from wood destroying fungi and termites. However, moisture contents of over 18% would have to be maintained before fungal attack can occur. Under these conditions or climates, Standard MDF should not be used.

While MR MDF is intended for use in moist or tropical areas, glue bond breakdown and fungal attack can occur if continually wet. Boards may be manufactured with fungicide additives or have a brush on post treatment preservative to protect against surface moulds which although are not wood destroying, will cause a certain amount of surface disfigurement under damp conditions.

Attack by wood destroying beetles is possible for both types of MDF, but it is unlikely to occur in Australia.

Moisture properties
MDF will respond to changes in relative humidity of the surrounding air. MDF should be conditioned to reach the humidity level in which it is to be used. Moisture contents will normally be in the range 10 - 12% when used in buildings intended for human occupancy.

Measurement of moisture content may be achieved by weighing and drying or by using an electric moisture meter.

Absorption and swelling
Moisture absorption by MDF causes swelling in the thickness. A small amount of residual swelling can also occur after the product has dried out. MR MDF exhibits a much slower response to wetting, which helps to minimize moisture effects over Standard MDF. Residual thickness swelling should not be an issue unless the panel has been continually wet.

Sizes

Standard MDF and Moisture Resistant MDF are available in a range of sizes, with the most common sheet sizes being 2400 x 1200 mm and 3600 x 1200 mm.

Check with individual manufacturers for available sizes.

Regulations / Standards & Codes

AS/NZS 1859.2 Reconstituted wood-based panels - Specifications - Dry-processed fibreboard provides all relevant properties and specifications for the various classes of fibreboard.

Product certification
The Engineered Wood Products Association of Australasia (EWPAA), formerly Plywood Association of Australia, has operated a quality assurance program since 1963. This ensures that the MDF manufactured by EWPAA members conforms to the relevant Australian Standard.

Formaldehyde emission classes
Depending on the standard and country of manufacture, MDF panels will fall under emission classifications E3, E2, E1 and E0. E3 is the emission class with the highest emissions and E0 is the lowest. E0 is also known as Ultra Low Formaldehyde Emission (ULFE).

If MDF is manufactured to Australian and New Zealand standards, the panel product will be clearly labeled with the appropriate formaldehyde emission class.

All Australian manufactured MDF must meet the E1, or Low Formaldehyde Emission standard.

Check with individual manufacturers for further information.


*Disclaimer : The species mentioned here are just a guide and for specific information refer to Suppliers Section

Description

Material Sub Type

Standard MDF 

Standard MDF is for interior applications only such as furniture and general fit outs. It is not suitable for areas that are prone to wetting or high humidity. 

 

Moisture Resistant (MR) MDF 

Like Standard MDF, MR MDF should only be used for interior applications. Being ‘moisture resistant' means it is suitable for high humidity areas and occasional wetting - areas such as bathrooms and laundries and for furniture in tropical areas. It is manufactured using a special moisture resistant resin (melamine-urea formaldehyde). It's important to remember that moisture resistant does not mean waterproof.

Manufacturers will usually identify the product with a green colouration of the board.

Fire Resistance

Fire resistance in the form of a fire rating can only be applied to a total building element incorporating MDF, eg a door or paneling. A product can not be fire rated, but it is important to note when a product is labelled as fire resistant or fire retardant it is referring to its ability to limit ignition, flame propagation, heat and smoke release.

Standard MDF has similar properties to that of natural timber when it comes to fire resistance and registers the following results under AS1530 - Part 3 Methods of fire tests on building materials. components and structures - Simultaneous determination of ignitability, flame propagation, heat release and smoke release:

Ignitibility: 14
Spread of Flame: 7-8
Heat Evolved: 6-7
Smoke Developed: 3-4

AS/NZS 3837 Method of test for heat and smoke release rates for materials and products using an oxygen consumption calorimeter takes into account the use of MDF for applications such as wall and ceiling panels. The EWPAA testing achieved the following results for raw MDF:

AV Heat Release: 84kW/m2
AV Specific Extinction Area: 72m2/kg
BCA Group Classification: 3

For more detailed information about fire resistance and the use of building materials, please refer to the Building Code of Australia (BCA).

Adhesives

Standard MDF uses a formaldehyde-based resin, which is thermosetting. Standard MDF generally uses urea formaldehyde, while MR MDF uses melamine urea formaldehyde to provide moisture resistant properties.

Adhesives for jointing
Due to the non-directional grain, MDF provides a good all-round gluing surface, with simple glue joints the best.

A urea-formaldehyde (UF) or a high viscosity PVA adhesive should be used for board to board joints, with adhesive applied to both edges.

These adhesive types are also suitable for edging or veneering with wood, while it is best to use a UF adhesive for plastic laminates.

The paraffin wax used in the manufacture of MDF may affect the curing of certain adhesives.

Treatments

MDF can be manufactured with fungicide additives or have a brush on post treatment preservative to protect against surface moulds under damp conditions.

Surface treatments can be used to protect against water and dirt, however it is important to check with each manufacturer as to the suitability and/or recommended products.

Paint can also be considered a surface protection.

Design/Engineering Considerations

MDF is generally an interior-use only timber material. Any exterior use should only be as per the manufacturer's guidelines.

MDF should not be used where persistent wetting is likely as this can adhesive failure and/or fungal attack. Moisture resistant MDF is susceptible to the same issues as standard MDF and while it can stand occasional wetting it should not be exposed to continual wetting as this can eventually cause adhesive failure or fungal attack.

Swelling is also likely to occur if subjected to moisture absorption. MR MDF should be also be adequately sealed or treated to reduce risk of swelling. MR MDF exhibits a much slower response to wetting than does standard MDF.

MDF has a low thermal capacity like natural timber.

Table - Typical property values for standard MDF:

Property

Thickness class - mm

Units

<5

6-12

13-22

>23

Density

Kg/m3

800-850

775

725

650-700

Bending strength (MOR)

MPa

44

42

38

30-40

Bending stiffness (MOE)

MPa

3800

3500

3300

3200

Internal bond strength

MPa

1.15

1.0

0.75

0.6

Surface soundness

MPa

0.7

1.0

1.3

1.4

Screw holding - face

N

-

-

800

850

                             - edge

N

-

-

1150

1000

Thickness swell (24 hr)

%

20-30

10-20

8-12

5-8

Formaldehyde E1 (Desiccator Method)

Mg/L

0.7-1.0

0.7-1.0

0.7-1.0

0.7-1.0

(source: EWPAA)

Table - Typical property values for MR MDF:

Property

Thickness class - mm

Units

<5

6-12

13-25

Density

Kg/m3

820-850

750-810

700-750

Bending strength (MOR)

MPa

55

45-60

40

Bending stiffness (MOE)

MPa

4250

4250

3750

Internal bond strength

MPa

1.6

1.2

1

Surface soundness

MPa

1.1

1.3

1.5

Screw holding - face

N

-

-

800

                             - edge

N

-

-

1400

Thickness swell (24 hr)

%

18

6-10

4-5

Cyclic test - internal bond

MPa

0.8

0.6

0.3-0.4

Cyclic test - thickness swell

%

12

10

5-10

Formaldehyde E1 (Desiccator Method)

Mg/L

0.7-1.0

0.7-1.0

0.7-1.0

(source:EWPAA)

Table - Dimensional tolerances for MDF:

Property

Units

Tolerance

Length & width

mm

+5 - 1.5

Length & width (cut to size)

mm

+2

Thickness - unsanded

mm

+0.4

Squareness

mm/m

1.5

Edge straightness

mm/m

1.5

(source: EWPAA)

 

Handling, Storage & Protection

During transportation, MDF should be protected by a waterproof covering and fully supported on equal size bearers. Edges, corners and bottom sheets need to be fully protected from damage and care taken to avoid any product damage. Boards need to be stacked correctly in order to avoid distorting or damaging material.

Pre-finished boards need to be handled with care to avoid any surface contamination, while surfaced boards should be always be lifted when being moved rather than sliding.

MDF boards need to be stored in an area that is protected from sun, rain and wind so that rapid changes in temperature and humidity are avoided. This will also help to avoid any surface staining or fading. If boards need to be stored outside they should be well protected with a tarpaulin or equivalent covering and need to be kept well clear of the ground.

For use in dry warm areas the moisture content should be kept as low as possible to avoid shrinkage after installation.

Boards stored on site, ie for a residential build, can better adjust to the moisture content of the surrounding environment. Each sheet should be stacked to allow free circulation of air.

It is advisable to check with individual manufacturers about how moisture content may affect certain applications.

Health and safety
When working with MDF, it is important to be aware of the potential risks of working with wood dust and formaldehyde. Inhalation of excessive amounts of wood dust can pose a serious health risk so it is important that proper precautions are taken.

Cutting or sanding should only be undertaken in a well-ventilated area. To avoid potential exposure to wood dust it is recommended that a Class P1 (Particulate) respirator, dust-proof goggles, gloves and long sleeves are worn at all times.

Formaldehyde gas is not likely to be released unless boards are being heated, laminated or laser cut. If undertaken in a well-ventilated workplace then formaldehyde emissions are unlikely to exceed industry standards.

Each manufacturer should have a Material Safety Data Sheet (MSDS) which provides information on health and safety issues associated with each product. Please contact the manufacturer directly to ensure you have the most up-to-date information.

It is important to stack MDF panels correctly

Cutting Holes & Notches

MDF can be worked with standard woodworking tools. The non-directional grain makes it easy to work with and it can be easily be drilled without splinters or chipping. MDF can be sawn, routed, spindled, planned or bored.

Maintenance

Excessive wetting should be avoided when cleaning. Check with manufacturer for advice on best proprietary products to use.

Workability

Due to its manufactured form, MDF offers a non-directional grain making it easy to work with. MDF is ideal for painting, cutting, machining and drilling without splinters or chipping. It also has advantages over particleboard in screw holding ability, internal bond strength and modulus of rupture.

MDF has a fine, smooth surface which is ideal for shaping or routing. It delivers a surface free of knots and grains - so is easier for finishing.

Fibreboards based on radiata pine have a very smooth surface, are easy to work and edges can be smoothly contoured. The material is a good substrate for high gloss coatings, decorative overlays and is also attractive in its raw form with a clear finish.

Sustainability

The wood used in the production of MDF is usually sourced from a renewable resource such as a plantation grown pine species or from waste off-cuts from sawmills.

Joints & Connectors

MDF can be permanently fixed by nailing or screwing.

Bullet head nails can be punched below the surface of MDF where a painted finish is required. Nail spacing should be as per manufacturers instructions.

The type and density of the board used will affect the screw holding capacity. A pilot hole may be required to help avoid splitting and if further strength is required then a solid wood insert or special fastening should be used.
Knockdown fastenings should be used if reassembly is required.

Finishes

MDF can be clear finished, painted, covered in wood veneers, high and low pressure laminates, papers, PVC film and fabrics.

MDF can also be edge profiled and painted to match the colour of the facing panel.

Clear finishes
The application of a clear finish provides a wear-resistant coating and details the natural form. For applications such as wall linings or ceilings, a one-part polyurethane coating will provide a good wearing clear finish.

Painted
Due to its smooth surface, MDF is easily painted. It is important to note that painting MDF can highlight the very small holes that are present in the finished surface, so to ensure the best finish is achieved a filler should be used. An oil-based paint will deliver a better result where MDF is to be used for kitchens or bathrooms. Emulsion and other water-based paints tend to swell surface particles of the wood panels which can result in a textured finish.

With acrylic paint systems, an exterior-grade primer should be applied first, followed by undercoat and two coats of acrylic gloss or semi gloss. Sanding before final coats, and the use of a semi gloss finish will minimise texturing.

High pressure laminates
Plastic laminates provide a durable, easy to clean surface finish and are well suited for use as benchtops and kitchen units.

Low pressure melamine
Melamine-surfaced MDF, produced by curing melamine resin impregnated papers, provides excellent wear resistance. Low pressure melamine finishes are used for cabinets, cupboards, built-in robes and other furniture products. A range of surface finishes are available as per manufacturers' specifications.

Papers/fabrics
Papers and foils offer a range of decorative choices, including wood grain finishes. Plain paper can be used as a base for further finishing. Decorative patterned or wood grain finishes. Papers are also available with a clear protective coating, eg polyurethane.

Fabrics can be bonded to MDF using UF or PVA adhesives.

PVC film
This is generally used for furniture such as wall units, desks and cabinets. A range of designs are available, including wood grain print or solid colours. PVC film is not generally recommended for horizontal work surfaces.

Veneers
Decorative wood veneers provide an impressive finish to MDF substrate.
Find out more about Decorative Veneers.

Edging
Edges can be veneered easily to provide a matching finish to the panel. Alternatively, a plastic strip with a toothed tongue on the back face can be pressed into a thin groove cut in the edge of the board.

Applications

  • Doors

    Timber is one of the most popular and superior material choices for both internal and external doors. Whether manufactured from solid or engineered timber, there are many stylish and practical options that won't compromise on strength and structural performance. A distinctive timber door can also create visual impact, adding value to any commercial or domestic building.

  • Internal Paneling

    Timber paneling creates interiors as warm as they are stylish. Commonly using an MDF or plywood substrate, internal timber paneling is natural and versatile and comes as either solid natural timber panels or as sheets of engineered wood products

Case Studies

  • Kew House 3

    Vibe Design Group’s, Kew House 3 uses timbers natural warmth and appeal to not only wrap a dynamic exterior but also evoke a journey of discovery within the home.

    Applications : Decking, External Cladding, Fencing, Flooring, Timber Joinery Products,

  • Letterbox House, Blairgowrie

    A holiday home that uses a range of commercial timber products and salvaged on-site timber to award winning effect.

    Applications : Architectural Roof Trusses, Doors, External Cladding, Fencing, Flooring, Framing, Windows,

  • Lewis St House, Thornbury

    A stunning residential renovation and addition that uses timber and timber products throughout with a commitment to sustainable design.

    Applications : Architectural Roof Trusses, Doors, External Cladding, Flooring, Framing, Interior Stairs, Windows,

  • NMIT Arts & Media Building, New Zealand

    A world first for its innovative use of LVL in the structure of a multi‐storey building, the NMIT building also incorporates a new generation of earthquake-­resistant engineering technology.

    Applications : Doors, Framing, Interior Stairs, Internal Paneling, Shear walls, Structural Timber Poles,

  • The Dickson Apartments, Little Bay

    An innovative coastal refurbishment where the use of timber contributed to an environmentally sustainable development while respecting the site's heritage significance.

    Applications : Doors, Exterior Rails and Balustrades, Exterior Stairs, External Cladding, Fencing, Framing, Interior Rails and Balustrades, Interior Stairs, Internal Paneling, Retaining Walls (Landscaping), Timber Portal Frames, Windows,

  • Yuille Park Community College

    A school becomes an integrated community hub where the versatile qualities of timber are used throughout to create an award-winning learning environment.

    Applications : Flooring, Framing, Internal Paneling, Shear walls,

Result(s) page 1 of 1

All Comments (1)

Sign In or Sign Up now to post a comment!