Processed board or sheet materials such as plywood, strandboard, hardboard and chipboard are collectively known as panel products and are made up of wood in the form of strips, veneers, chips, strands or fibres. This material can also be made up in non-sheet form such as chipboard (sometimes known as composite) blocks particularly used as deck spacers in pallets, see figure below. Sawn wood, even when accurately machined and having been kiln dried or planed, is not defined as processed wood. Plywood was developed to provide large panels with a dimensional stability lacking in sawn timber without jointing and good strength properties along and across the sheet. Straight well-grown logs are required for peeling the veneers for plywood manufacture. The categories usually recognised within this group that are used in packaging are:-
Particleboard pallet blocks
- Plywood sheet
- Waferboard and oriented strandboard (OSB) sheet
- Wood chipboard or composite wood blocks, particularly used in pallets,
- Wood chipboard sheet also known as wood particleboard sheet
- Fibre building board including hardboard and medium density fibreboard (MDF)
Wood particleboard and fibre building boards were developed to provide utility sheet materials with uniform properties. They often utilise forest thinnings, lower quality trees, sawmill waste or reclaimed waste wood. The main end use in packaging is for pallet blocks with small amounts used in printers pallets where dryness is essential. Wood-based panel products are covered by a series of EN Standards but unlike previous standards, which were largely prescriptive and based on manufacturing requirements, new ENs are based on performance requirements such as the water resistance of gluelines and limiting formaldehyde gas emissions. Appropriate grades of board materials for packaging are as follows:
Plywood with a water resistant glueline is historically known as WBP, but more recently by the European standard term Exterior, is suitable for most end uses but for export to Australia there is a need for unusual phytosanitary safeguards (see ISPM 15 page for details). Water resistant exterior glueline plywood can be used for long term packaging but whilst defining specification to plywood suppliers is easy, it requires considerable experience to ensure you receive this grade. The pitfalls of using interior gluelines and/or species which discolour with mould or sapstain in damp conditions are often seen in packaging.
OSB (oriented strandboard) and waferboard is classed with plywood as it is made in a similar manner, most end uses can be the same.
Wood chipboard is heavier as a sheet material and is less strong than plywood, but as short block material for pallets it is widely used and as strong as sawn timber. The main problem with block material is knowing the wet strength since all packaging gets wet and some unbranded material may delaminate in very wet conditions. As sheet, wood chipboard is not a normal choice except where used for printing trade pallets since it is always supplied in a very dry state.
Fibre building board is available in Standard or Tempered (has moisture resistance) Grade and is used for light packing case sheathing.
New materials such as finely chipped rubber from scrap vehicle tyres have been introduced as pallet blocks but the low percentage of wood in the mix means they are not classified as timber. Such material can be nailed as well as timber and can also have good compressive strength.
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73c Composite chipboard and plastic recyclate pallet blocks (PDF 52kb)
73d Comparing wood chipboard with solid timber for pallet blocks (PDF 40kb)
74c Five types of wood-based sheet material (PDF 30kb)
77b Reading mdf and particleboard with a moisture meter (PDF 11kb)
77h Assessing good quality composite chipboard blocks for pallets (PDF 11kb)
85f ISPM 15 - Treated wood packaging imported into the EU reused in Europe (PDF 17kb)
85g ISPM 15 - Portugal - New phytosanitary requirements 2009 (PDF 18kb)
85h ISPM 15 - Australia - New requirements for imported plywood - June 2009 (PDF 18kb)