BS ISO 21546:2019 pdf download – Paints and varnishes – Determination of the resistance to rubbing using a linear abrasion tester (crockmeter)
5.4Abrasive material, for lining the abrasion tool
5.4.1 Cotton rubbing cloth, in accordance with ISO 105-F09 with a mass per unit area of (110±5)g/m2 and 36 threads/cm in both directions.
5.4.2 Abrasive paper, with agreed grain size in accordance with FEPA standard 43-2 and preferablyself-adhesive.
5.4.3 Abrasive material, with agreed grain size in accordance with FEPA standard 43-2, attached to asoft supporting material.
5.4.4 Felt, made of a material with agreed properties (e.g. bulk density and felt hardness according toDIN 61200).
5.5Abrasive medium
Abrasive paste, abrasive powder, etc. of agreed type and/or water in accordance with ISO 23321, forsprinkling/wetting the abrasive material and/or the coating prior to rubbing.
5.6Tools for assessing the friction marks
Depending on the agreed evaluation method, e.g. a measuring device for determining the gloss (seeAmnnex C), the haze, or the brightness, is necessary, in combination with a measuring template (seeAnnex B) or aset of comparison pictures.
6Test specimens
6.1Test specimens
The test specimens shall be plane and prepared, coated, and dried/hardened in accordance withISO 1514.The width of the test specimens shall allow for the possibility that three tests can becarried out next to each other without edge influence; the lengths of the test specimens depend on theconstruction of the test device.
NOTE Normal test specimen dimensions are 100 mm x 150 mm.
The surface of the test specimen shall be clean.Clean the surface with a soft, lint-free cloth and, ifnecessary, use a solvent which does notattack the coating.
6.2Film thickness
Determine the dry film thickness of the coating, in micrometres, in accordance with one of the methodsgiven in ISO 2808.
Prior to testing, condition the coated test specimens at a temperature of (23 ± 2) °C and a relativehumidity of (50 ±5) % in accordance with ISo 3270, if not otherwise agreed, for a minimum of 16 h.
7 Procedure
7.1Test conditions subject to agreement
For the test procedure and the evaluation of the test the following shall be agreed:-the abrasion tool in accordance with 5.2;
-the abrasive material in accordance with 5.4;-the abrasive medium in accordance with 5.5;-the number of double-strokes;
the evaluation criterion, e.g. measurements of gloss, haze or brightness, visual comparison withreference pictures, etc.;
– the time interval between abrasion and evaluation of the friction marks.Examples of usual test conditions are given in Aonex A.
7.2Test environment
Carry out the test at a temperature of (23 ± 2)°C.Measure the relative humidity during the test andrecord in the test report.In case of high relative humidity,be careful that no condensation water formson the test specimen due to falling below the dew point.
Carry out the test as quick as possible, however, not later than 30 min after the conditioning phase.7.3Testing process
7.3.1If the friction marks are assessed by agreement using optical measurements, e.g. gloss, haze orbrightness, determine — preferably using the measuring template (see Annex B)—on the test panel atleast three linearly spread measurement points and mark them.
The measurement points shall be determined such that:
– the measuring areas do not overlap;
– they are spread evenly on the (expected) friction. mark;