EN 927-5-2006 pdf download.Paints and varnishes – Coating materials and coating systems for exterior wood – Part 5: Assessment of the liquid water permeability.
5.3.3 Coating application
Coating systems shall be applied according to the manufacturers specifications.
Apply each test coating system to the test face only (convex side of the panels).
Each coating system under test requires 3 test panels (340 mm x 70 mm x20 mm).
When the coating systems have dried, cut a test panel 150 mm in length from both ends of each long panel (see Figure 2).
The three small coated off-cuts C are used for the determination of film thickness,
Three additional panels are required to check the test face with the selected sealer. This sealer and the number of layers should be identical with the later on used sealer for sealing the test panels (150 mm x 70 mm x20 mm). The liquid water permeability of the sealer shall not exceed 30 gIm2 in 72 h (see Figure 2).
Additional information is given in Annex B.
5.3.4 Sealing and conditioning
Panels shall be sealed in the same way whether they are applied for test coatings or control of sealer. Seal the sides, end-grains and reverse faces of the panels against water entry using at least two coats of a flexible moisture-impermeable coating, for example a solvent-free epoxy or polyurethane paint. The sealer shall cover the edges completely and overlap the test face by 2 mm (see Figure 3). Apply the sealer to the end grain so many times that a closed and uniform film is obtained.
5.3.5 Dry film thickness
Determine the dry film thickness of the coating on the off-cuts (see Figure 2) of the test panels. Remove one small chip of coated wood from each of the off-cuts and examine by microscopy in accordance with prEN ISO 2808:2004, method 6A. Make 5 measurements on each chip and calculate and record the mean value in micrometres.
The dry film thickness is defined as the thickness of the layer on (above) the wood surface, Systems may penetrate the wood material to some extent, but this part is not included in the determination.
6 Apparatus
6.1 Microscope for measurement of dry film thickness In accordance with prEN ISO 2808:2004, method 6A.
6.2 Conditioning room, of appropriate size, controlled at a temperature of (20 ± 2) C and a relative humidity of (65 ± 5) %, In accordance with ISO 554.
6.3 Container for deionized water, of size sufficient to hold the all the panels under test.
6.4 Balance, capable of weighing to the nearest 0,01 g.
7 Procedure
7.1 Pre-conditioning
It is known that the water permeability of some types of coating can change markedly during a relatively short period of exposure to water. For such coatings the values of water permeability obtained during a short period of contact with water might not be representative of those obtained during long-term service. For this reason all panels shall be subjected to a leaching procedure before commencement of the absorption cycle.
This procedure shall be carried out twice as follows:
— 24 h floating face down in deionized water, such that the test face is fully submerged;
— 3 h drying at (20 ± 2) C and a relative humidity of (65 ± 5) % in accordance with ISO 554;
— 3hdryingat5o°C;
— 18 h drying at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with ISO 554.
All panels shall be handled together.
After 72 h remove the test panels from the water, blot lightly to remove any water droplets and weigh. Record the elapsed time and mass (m1).
All handling of the panels shall be carried out in the conditioning room (6.2).
7.3 Optional testing of weathered panels
If required, coatings may be subjected to a weathering test before or after measurement of liquid water permeability.
8 Calculation and expression of results
At the end of the test calculate the water uptake m, – m0, in grams, for each test panel.
Calculate the water absorption per square metre of test surface for the test panels by dividing the water uptake by the measured test area of each of the test panels. Finally calculate the mean value of the individual measurements.
Mean value, standard deviation and coefficient of variation shall be stated in the test report,
If the water absorption of the test panels with the sealer exceeds 30g/m2 in 72 h the test is not valid.
9 Precision
9.1 Repeatability (r)
The repeatability r is the value below which the absolute difference between two single test results, each mean of duplicates, can be expected to lie when this method is used repeatability conditions. In this case, the test results are obtained on identical material by one operator in one laboratory within a short interval If time using the standardized test method. In this standard, r is 9,1 (32,7 % relative to the mean value) for brush application systems. and 12 (15,3 % relative to the mean value) for spray coating systems, with a 95 % probability
9.2 Reproducibility (R)
The reproducibility R is the value below which the absolute difference between two single test results, each the mean of duplicates, can be expected to lie when this method Is used under reproducibility conditions. In this case, the test results are obtained on identical material by operators in different laboratories using the standardized test method. In this standard, R is 15,9 (57,7 % relative to the mean value) for brush application systems, and 23,1 (29,6 % relative to the mean value) for spray coating systems, with a 95 % probability.EN 927-5-2006 pdf download.
EN 927-5-2006 pdf download
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