Reconstituted Panel Products Print E-mail
Reconstituted Panel Products are produced by reducing woody material to small particles and reconstituting them into large sheets of the desired thickness. These sheet materials are easy to handle and erect, enabling large areas to be covered quickly and economically. The main types of Reconstituted Panel Products available are:
  • Wet-processed fibreboards (principally softboards and hardboards);
  • Dry-processed fibreboards (principally MDF); and
  • Particleboards.

A. Wet-processed Fibreboards (Softboard and Hardboard)

Wet-processed fibreboard, as produced in Australia, is made from eucalypt fibres. The fibres are suspended in water which gives rise to the name "wet-processed". They are fed onto an endless belt; the water is removed by suction; the ribbon of board is cut into desired lengths and stacked in a hot press to complete the bonding process. Because adhesives are unnecessary, eucalypt-based hardboards have obvious advantages in view of the rapid increase in the cost of bonding agents.

Softboards
Often called "softboard" or "insulating board", this board is made from softwood fibres felted together but not consolidated by heat and pressure. The board is used for wall and ceiling lining to provide acoustic and thermal insulation.

Hardboards
There are three classes of hardboard:
  • GP, for general purposes not subject to weathering;
  • MR, a board promoted for internal use in humid, areas, such as bathrooms. It is heated with linseed oil in the final stages of manufacture and sold as tempered hardboard; this treatment also increases its modulus of rupture.
  • Exterior, hardboard made from selected hardwoods. The fibres are given extra steaming to remove material that could be attractive to fungi. A small amount of wax is added to improve the board's water repellent properties and the curing pressure is adjusted to provide a medium density board - with enhanced stability. Such medium density exterior grade hardboard is a good cladding material - which is stable, free of edge swelling and an outstanding substrate for all types of coating. It has good resistance to impact damage and denting, is non-corrosive, has good insulating properties and is easy to cut and nail.
The equilibrium moisture content of hardboard is much lower than that of timber, varying between a half and three-quarters of the figures obtained for the natural wood. However it still needs conditioning to the environment in which it is to be used before being fixed in position.

Australian Standard AS 1859.4 provides definitions, dimensions and tolerances, and the requirements for properties such as bending strength and thickness swell in water. For exterior grades it also specifies internal bond and wet bending strength.

Hardboard of an appropriate type is used for pre-finished panelling, sheet floor underlayment, cladding, door facings, perforated display boards, eaves lining, television cabinet backs, automotive components, concrete formwork and roof and wall shingles.

B. Dry-processed Fibreboards

Dry-processed fibreboards are made with a fibre mat containing only about 10 percent moisture. Bonding is achieved by the addition of synthetic resin adhesives which are cured under heat and pressure.
There are a number of different classes of dry-processed fibreboard available, including ultra low density, low density, medium density and high density classes. AS/NZS 1859.2-2004 provides all relevant properties and specifications for the various classes. The most commonly produced and used class is medium density fibreboard or MDF. Both standard medium density fibreboard (STD MDF) (dry use) and moisture resistant medium density fibreboard (MR MDF) classes of MDF are produced for internal use and are differentiated by the adhesive used during production.

Remember: Moisture resistant does not mean waterproof.

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. It has advantages over particleboard in screw holding ability, internal bond strength and modulus of rupture.

AS/NZS 1859.2-2004 notes that:
  • Neither MR MDF nor HP MDF (high performance) should be used where persistent wetting is likely. If fibreboard is left in continuously wet conditions, degradation will occur through adhesive failure and/or fungal attack.
  • Exterior use should be strictly in accordance with the manufacturer's recommendations, instructions and guidelines.

Fibreboard containers
An unfortunate confusion arises from the common application of the word "fibreboard" to the cardboard-like material which constitutes the common container used especially for the conveyance of fruit and vegetables to market and for the bulk packaging of most grocery merchandise.
Such material, more akin to a thick paper, is of course a very different product from the fibreboards discussed above.

C. Particleboards

Particleboard is a panel product made from relatively large particles instead of fibres and is dependent for its strength and durability on the type and quantity of adhesive used to bond the ingredients together. Other terms such as "chipboard", "waferboard", and "flakeboard" are used to describe panel products of similar type but differing in particle size. The Australian Standard AS/NZS 1859.1-2004 describes three types:
  1. Standard general purpose particleboard (STD), intended for internal use in dry conditions, such as in the construction of furniture (often with a veneer overlay), cupboards and shelving. Urea formaldehyde resin is the usual binder. STD particleboard is sometimes used as a decorative wall facing but it is important that each room be faced with material from the same manufacturer, and preferably the same batch, to ensure uniformity of appearance.
  2. Moisture resistant general purpose particleboard (MR), intended for internal use in humid conditions where occasional wetting may occur, such as in bathrooms and kitchens. A proportion of particleboard is sold as Low Pressure Melamine (LPM) coated board, often in the form of "whiteboard" where a white overlay colour is used.
    Remember: Moisture resistant does not mean waterproof.
  3. High Performance particleboard (HP) intended for use in:
    1. continuously humid conditions such as occurs in tropical climates or where occasional wetting in interior conditions followed by drying may occur; or
    2. loadbearing applications in dry and humid conditions.
AS/NZS 1859.1-2004 notes that:
  • Neither MR nor HP particleboard should be used where persistent wetting is likely. If particleboard is left in continuously wet conditions, degradation will occur through adhesive failure and/or fungal attack.
  • Exterior use should be strictly in accordance with the manufacturer's recommendations, instructions and guidelines.


Particleboard Flooring
AS/NZS 1860 Part 1 defines two classes of Particleboard Flooring:
  1. Class 1 flooring, for internal flooring, manufactured with an adhesive which does not deteriorate in the presence of moisture or dampness. This grade is suitable for limited exposure during construction. Phenol formaldehyde and tannin formaldehyde water proof adhesives are most commonly used. Most flooring grade particleboard production is of class 1 which is destined for use in Australian conditions.
  2. Class 2 flooring, for internal flooring, but only in locations where there is no risk of dampness. Urea formaldehyde is the most commonly used adhesive in its manufacture. The class 2 board is appropriate for upper-storey floors or for ground floors where permanently dry under-floor conditions are assured. It is unsuited for tropical areas of high natural humidity.
    Note: Class 2 flooring is not suitable for use in Australia
Installation of particleboard flooring
The Australian Standard AS 1860.2-2006 sets out the conditions for using Class 1 flooring as well as providing information on the appropriate precautions to take when laying both platform and fitted flooring of particleboard. Platform flooring may be defined as the laying into permanently fixed position of the flooring material over the whole floor area as soon as joists are in position and before the internal and external wall framing is erected, to provide a safe working platform for the various tradesmen, and to speed up the erection of the building; it necessarily involves the exposure of the flooring membrane to the risk of considerable moisture uptake from dewfall and rain before the building provides full protection. Particleboard flooring should not be exposed to the weather for more than two or three months. Edge swelling is a characteristic of particleboard when exposed to moisture; the effect is limited virtually to the area within 50 mm of the edge but much of the swelling is not recoverable on drying so an appreciable amount of material may have to be sanded off at the edges to obtain a level floor if there has been a lot of exposure to the weather. This sanding is likely to expose particles of a different size to the main body of the sheet and have some effect on appearance. If the floor is to be covered this is not important.

Exposure of the particleboard to the weather for more than two or three months is likely to have an effect on its internal bonding strength and stiffness.

Particleboard flooring is not suitable for external decking.

Particleboard can be made termite resistant by preservative treatment to H2 level. (See: Treated Timber)



Australian Wood Panels Association
AWPA is an organisation formed to promote the use of reconstituted wood products such as MDF and Particleboard and further research and development to conserve the agricultural and forestry resources of Australia. 
 
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