Dr Vic Kearley, Section Leader, Engineering and Product Services, gives TRADA's view on the thorny issue of palm-cored plywood.
Is palm a wood? Based on a reported statement, dating back to 2004, by experts at the Botanical Gardens, Kew, palm is not a wood. As to the debate about whether it can be used to make a product that could be correctly described as plywood, the short answer is yes - as long as the product description is correct and there is sufficient test evidence available, specific to the product, to show that it is fit for purpose in all respects.
However - and here's the rub - the product description will vary depending on whether or not material from palm stems is classified as wood.
If palm stems can be classified as wood, then a panel made from veneers cut from them could be described as plywood, provided it met all the normal requirements for such material. For the sake of clarity, TRADA would recommend that the word palm be included in the product description, eg palm plywood, in the same way as is common for other plywoods of known species, eg birch plywood.
If palm stems are not accepted as wood, then a product with palm in the core but with external wood veneer, could be described as either
Palm core plywood or
Palm composite plywood
In either case the panel would have to comply with the requirements for these definitions as given in BS EN313-2: 2000 Plywood. Classification and terminology. Part 2: Terminology. This is the guidance given in a recent statement by BSI Committee B/541 and further circulated by NPPD (TTF). However, the statement was based on the assumption that palm cannot be considered asa wood and further investigation since the B/541 meeting has cast doubt upon this assumption.
Now for a bit of science. Chemically, palm stems are made of lignocellulosic material, like wood. Botanically, palms are members of the ‘ woody' Monocotyledons order of the angiosperm class of the spermatophyte division. This order also includes bamboo. Hardwoods are also angiosperms but come from the Dicotyledons order.
Hence there is a botanical difference between the classification of conventional hardwoods and the palms. Palm's microscopic structure is also different from hardwoods, with significant variation in structure and density along and across the stem. Palms lack the ‘lateral meristems' present in hardwoods, that allow for ‘secondary thickening', despite their tree-like appearance. So, despite being a member of the angiosperms, their structure and form differ from hardwoods.
However, in common parlance, trading and use terms, the situation is less clear. A growing palm is commonly referred to as a tree, even if its microscopic structure is different to a hardwood. BS 6100-1: 2004 Building and civil engineering - Vocabulary - Part 1: General terms defines wood as ‘lignocellulosic substance between the pith and bark of a tree or shrub'.
Most people would accept that palm material meets that definition, even though there are botanical differences between palm and softwood/hardwood.
The outward appearance of palm material is similar to wood and as a result has been reportedly viewed by Customs and Excise as wood ‘by association'. There are also many palm products that have been traded internationally as palm wood for many years in established markets.
In trading standards terms, there are precedents for products being described in terms of common English usage rather than scientifically accurate terms and this appears to be applicable to palm wood products. The timber industry sells its products primarily to other members of the timber trade, to the wood using industries and to the public, most of whom could not be expected to have an in depth knowledge of the botanical structure of the products they are buying.
Considering the above, TRADA now takes the view that such palm veneer products could correctly be described as palm plywood, and offered for sale on that basis. As such they can be tested and marked in accordance with BS EN 13986: 2004 Wood-based panels for use in construction. Characteristics, evaluation of conformity and marking and BS EN 636: 2003 Plywood - Specifications. To avoid any potential misunderstandings, however, it should probably not be described without the ‘palm' prefix. A simple description of ‘plywood' without reference to palm could be considered as misleading.
If such a product is to be used in non-construction applications, such as furniture, then the supplier needs to be able to demonstrate that it is fit for purpose, and this can simply be agreed between the supplier and the purchaser.
If the material is for construction use then, as with all plywood, the supplier needs to be able to demonstrate compliance with the Construction Products Directive (CPD), which is implemented in the UK through the Construction Products Regulations 1991 (amended 1994). For a product qualifying as ‘plywood', the most straightforward route for this is by demonstrating compliance with the CE marking requirements of BS EN 13986. However, in the case of panels containing palm-based materials, the assumptions which allow ‘Classification Without Further Testing' (CWFT), for properties such as reaction to fire, should not be assumed to be applicable without supporting test evidence.
It is therefore clear that a much greater degree of testing will be required for these materials than for more conventional plywood. The extent of testing required will depend upon the end use and whether the panel is intended for structural or non-structural use, but might include tests for durability, reaction to fire, mechanical properties (short and longer-term), stability and so on. It's back to that well worn phrase, caveat emptor. Know what you are buying and ask for evidence that it does what it says.
If for any reason a specific product does not meet the definition of plywood as described in BS EN 313-2 and BS EN 636, then it cannot be assessed against the requirements of BS EN 13986 and alternative means of demonstrating compliance with CPD must be sought. This could be through performance testing linked to independent product certification, such as that offered by BM TRADA Certification. An alternative solution could be to CE mark via the development of a CUAP (Common Understanding of Assessment Procedure) and issuing of an ETA (European Technical Approval). For further information on developing palm-based products for construction and other markets within the European Union, email or telephone 01494 569600.
