BS/EN 927-13-2019 pdf download.Paints and varnishes — Coating materials and coating systems for exterior wood Part 13: Assessment of resistance to impact of a coating on a wooden substrate.
3.3
cracking
rupturing of a dry film or coat
[SOURCE: EN ISO 4618:2014. 2.65, modified — Notes have not been included.j
3.4
flaking
detachment of small parts of a coating due to a loss of adhesion
[SOURCE: EN ISO 4618:2014,2.114)
4 Principle
A cylindrical steel weight is dropped from specified heights through a vertically-mounted guide onto a steel ball of specified diameter and hardness positioned on the test panel. The degree of damage to the test area is assessed by reference to a descriptive numerical rating code.
5 Apparatus and materials
5.1 HorIzontal base which provides rigid support for the test panel.
5.2 Vertically-mounted guide tube with an inside diameter of (40 ± 5) mm (1 in Figure 1). A (10,0 ± 0,5) mm thick disc with a centre hole of diameter (14.25 ± 0,25) mm for the balI (5.4) shall be attached to the bottom end of the guide tube.
5.5 Microscope (magnifier) with a magnification of at least x 10 for the assessment of surface
defects.
6 Procedure
6.1 Wood panels
Boards of Norway spruce (Picea abies (U. Karst) are selected with normal growth rate (i.e. 3 annual rings to 8 annual rings per 10 mm). a density between 0.4 g/cm3 and 0,5 g/cm’ (measured after conditioning) and straight grain. The wood shall be free from blue stain and evidence of surface or bulk fungal infection. Abnormal porosity (caused by bacterial attack) shall be avoided (see EN 927-3:2019,A.10). From these boards, panels with the minimum dimensions 170 mm x mm. 70 mm x (20 ± 2) mm free from knots, cracks and resinous streaks are produced so that the inclination of the growth rings to the test surface is 600 to 90°. The panels shall be planed to a smooth and uniform finish. In order to avoid aged wood surface, the panels shall be hand sanded (mesh 150) immediately before coating.
The wood shall be conditioned at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with lSOSS4 to an equilibrium moisture content of (13±2)%. After conditioning wood density is determined according to ISO 13061-2.
6.2 Coating application
For each system, select three panels on a random basis from the available supply. Apply the coating system to the front side of one panel using the method specified by the manufacturer to give a wet film thickness corresponding to the mean value ± 20 % of the manufacturer’s recommended spreading rate. Record the quantity of coating applied. The values should be stated preferably in grams per square metre, but may also be expressed as wet film thickness (in micrometres).
After coating application, age the panels for 21 days in the controlled environment at (20 ± 2) °C and a relative humidity of (65 ± 5) % in accordance with ISO 554.
6.3 Assessment of resistance to impact
6.3.1 General
No impact point shall be less than 15 mm from any edge of the test panel. The centres of impact points shall not be less than 15mm apart. lithe grid pattern method detailed In 6.3.2 Is to be used, then eight lines spaced at least 15 mm apart shall be marked out on the surface that is to be tested. The lines shall be perpendicular to the direction of grain. Three impact points spaced at least 15 mm apart shall be marked off along each line (see Figure 2).
Either make a random selection of impact sites, making provision to identify the dropping height for each site adequately, or preferably use the grid pattern described in 6.3.1 making three impacts on each numbered line with dropping heights as follows:
— on line 1 from a dropping height of 10 mm;
— on line 2 from a dropping height of 25 mm;
— on line 3 from a dropping height of 50 mm;
— on line 4 from a dropping height of 100 mm;
— on line 5 from a dropping height of 10 mm;
— on line 6 from a dropping height of 25 mm;
— on line 7 from a dropping height of 50 mm;
— on line 8 from a dropping height of 100 mm.
For each test, position the guide tube (5.2) on the test area with the ball (5.4) in direct contact with the surface. Drop the cylindrical weight (5.3) once from the specified height onto the ball.
After each Lest, the ball should be examined for possible deformation and if necessary replaced by an undamaged ball.
Alter completion of the Lest, the application of penetrating stain or other suitable marker (like whiteboard marker of suitable colour) to the test area can assist with the identification of surface cracks. After Few seconds after marking, carefully wipe the impact mark with the soft paper towel to remove residue of the marker.
6.3.3 ExamInation of test panel
Carefully examine the test area under magnification and good direct light using the following procedure.
Keeping the test area directly under the light, rock the panel or the light, so that the angle between the direction of the light and the plane of the panel varies between 0° and 30°. During the rocking movement, examine the test area using the microscope (5.5).
Turn the test area of the panel through 90° and repeat the procedure.
6.3.4 Assessment of results
Rate the test areas according to the descriptive numerical rating code in Table 1 (see also Figure 3).BS/EN 927-13-2019 pdf download.
BS/EN 927-13-2019 pdf download
PS:Thank you for your support!
