Evaluation of the european standard ENV 12038 for durability testing of plywood
J Van Acker, M Stevens, E De Clercq
The latest improved version of the standard ENV 12038 drafted as document N44 by CEN Technical Committee 38 (WG 7 - WG 23) is used to evaluate the effect of wood composition and structure on plywood durability. The method described is based on the agar-block test of the EN 113 standard used for the determination of the efficacy of wood preservatives and the assessment of the natural durability of timber. This test method differs from the soil-block test commonly used in North America and vermiculite test procedures used earlier for plywood testing. The ENV 12038 method is essentially developed to deviate minimal from the European basidiomycete tests currently established. Therefor it was important to evaluate whether or not vermiculite or soil as a test medium could be replaced by a malt- agar medium using an adequate preconditioning of panel specimens prior to fungal testing. Based on two consecutive experiments both test methodology and the assessment of plywood durability are investigated. Plywood is a material that allows a direct evaluation of test methods for assessing the durability of board materials in comparison with test methods used for solid wood. The presence of glue-lines and the layered structure based on solid wood veneers enables to investigate in detail the impact of wood composition as well as the type and amount of glue. Preconditioning plywood prior to testing according to ENV 12038 proved to be essential. However the impact of the glue is not entirely eliminated that way.