Research project PA/04 (Research action PA)
The project proposal ‘PERFORMANCE ASSESSMENT OF COATING SYSTEMS FOR EXTERIOR JOINERY’ provides a practical methodology to identify exterior wood coatings adequate to protect exterior joinery and allow wood to remain a reliable and cost effective material in this sector. Based on the fact that European harmonisation under CEN standardisation failed up to now to implement methods in this way, the work is actually focussing on the possibilities to use a combination of artificial ageing and (if required) biological testing as an alternative for natural weathering as an attempt to obtain fully reliable and reproducible results.
A range of well-defined and standardised assessment methods is now available from European (EN 927) and international standardisation (ISO) and is used to detect failure in performance as a mimic of insufficient performance of coatings in practice. As such critical values are derived for each of the assessment parameters identifying the level of performance considered adequate. The level of performance is used to develop a technical specification and eventually also initiate a system of certification for exterior wood coatings. The project therefore relies on coating systems supplied by paint manufacturers representing both adequate and inadequate performing coatings. Applications used for testing is similar to the ones in industry (industrial application) or as applied after installation of the exterior joinery elements (do-it-yourself or professional).
The methodology focusses on the use of artificial ageing as a reproducible test system to identify physico-mechanical degradation. Additional work includes maintenance since extra information both on frequency and the ease of reapplication are parameters to be considered when evaluating the overall performance of a coating system. If relevant also biological factors should be included. Since regularly failures due to these factors are present in our climate contrary to e.g. Mediterranean or continental regions, a worst case test set up for blue stain in service and mould behaviour is included for this purpose.
The consortium consists of a sector institute, a test laboratory and the related industry. The co-ordinating institute is responsible for the exterior joinery sector. The test laboratory is experienced and involved in testing according to the latest developed test methods and assessment criteria on European level. The collaborating industry partners provides both substrate and coatings needed to identify critical values to specify minimal requirements for adequate exterior wood coatings. Interaction of the entire consortium guarantees that low performance wood coatings known from practical experience is included hence covering all possible failure features. The test procedures should then be able to separate these from adequately performing coatings and to establish a test methodology that remains simple and easy to interpret. The fact that European standardisation provides the basic tools to do so and the need to develop adequate and standardised testing methods for exterior coatings improves the market position of exterior wooden joinery significantly. Furthermore the newly developed wood coatings that take into account low VOC requirements (waterborne and high solid coatings) and biocide restriction (NFX coatings – non-fungicidal exterior coatings) need substantial quality guarantee systems. Only this way confidence remains in the use of exterior wooden joinery and the coatings applied.
Performance assessement of coating systems for exterior wooden joinery : final report
Brussels : Federal Science Policy, 2007 (SP1828)
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