Artificial weathering plays an important role in the development of improved coating systems. However, there exists at present no agreed artificial weathering test applicable to wood substrates.The preparation of such a test forms part of the work programme of CEN/TC139/WG2 and this proposal sets out the programme of work needed to achieve it. The consortium supporting the application includes ten members of CEN/TC139/WG2. Different types of artificial weathering machines and operating cycles exist, but no reliable method applicable to the wide range of types of exterior wood coating system is available today. Most of the machines have shortcomings, and the purchase and operating costs of some type are so high as to place them beyond the reach of small enterprises. The lack of an agreed method applicable to wood coatings complicates the interpretation of results and the exchange of information between raw materials suppliers, coatings manufacturers and research organisations.
The approach adopted in this proposal is considered to constitute a significant advance for the following reasons:
(i) the objective will be to base the method on the modern and relatively low-cost fluorescent lamp apparatus originally developed for coated steel and plastic substrates, adapting the equipment and operating cycles to meet the needs of wood substrates.
(ii) the need to recognise the dependence of results on binder type will be taken into account.
(iii) test results will be analysed using modern reliability theory capable of handling the numerous and often interdependent factors influencing degradation phenomena.
(iv) in addition to the application of the customary methods for monitoring the development of appearance changes and physical defects during weathering, degradation will also be monitored by advanced analytical techniques for detecting basic chemical and physical changes, in order to exploit the predictive capabilities of artificial weathering.
New artificial weathering cycles are tested on selected coatings (application on wood during spring 97), in comparison with natural weathering which has started in July 97.
Funding SchemeCSC - Cost-sharing contracts
WD2 7JR Watford
SL2 5DS Slough
114 86 Stockholm