Test Methods for a Reliable Qualification of Waterborne Paints for Exterior Wood Protection

摘要

Water borne paint systems, which are applied in a relatively wet season, may promote cumulation of water in the wooden substrate. This behaviour is caused by an increase in moisture barrier properties due to leaching of water-soluble components and is funther promoted by the increasing barrier properties at relatively dry external conditions. Recent tests with four commercially available paint systems show an increase in μ-value with a factor 2.4 to 3.8, after a leaching period of only two weeks. Existing test methods and standards do not sufficiently take into consideration the effects of leaching on the moisture barrier properties. The reliable assessment of the quality of water borne paint systems for exterior wood protection needs new or adapted test methods and standards. Mathematical models have to be developed to translate laboratory test results to different real application conditions, climates and timber dimensions.