BS ISO 19403-5:2015 pdf download – Paints and varnishes — Wettability — Part 5: Determination of the polar and dispersive fractions of the surface tension of liquids from contact angles measurements on a solid with only a disperse contribution to its surface energy
Step 5: The polar fraction of the surface tension of the liquid is calculated from the dispersive fraction of the surface tension and the surface tension measured in step 1.
4 Reference solid Sufficiently chemically and topologically homogenous dispersive solid, e.g. made of paraffin or PTFE.
NOTE 1 For the application of this standard surfaces of solids with a polar fraction of < 0,5 mJ/m 2 are sufficiently dispersive.
NOTE 2 Sufficiently homogenous PTFE reference surfaces preferably have a surface free energy of (18,5 ± 0,5) mJ/m 2 in accordance with the OWRK method, whereas locally measured surface free energies on the reference surface for the determination of the standard deviation (see 7.1) are measured in accordance with 6.3.
For the PTFE surfaces as well as the paraffin surfaces precise reference objects with a mean roughness value R a
2) of less than 0,3 µm are to be preferred. The paraffin reference surfaces preferably have a surface free energy of (25,5 ± 0,5) mJ/m 2 under the same conditions as the PTFE reference surfaces. 5 Sampling Take a representative sample of the liquid to be tested in accordance with ISO 15528.
6 Procedure
6.1 Test conditions Carry out the test at (23 ± 2) °C and a relative humidity of (50 ± 5) % (see ISO 3270) and make sure that all test media have this temperature.
6.2 Determination of the surface tension of the liquid to be tested Measure the surface tension of the liquid to be tested in accordance with ISO 19403-3, EN 14370, or ISO 1409.
6.3 Determination of the surface free energy of the reference solid Measure the contact angle on the reference solid if unknown in accordance with ISO 19403-2. Use at least ten drops of each of at least three test liquids indicated in ISO 19403-2:YYYY-MM, Table 1, for this. Calculate the surface free energy of the reference solid in accordance with ISO 19403-2 in accordance with Owens, Wendt, Rabel and Kaelble or Wu. NOTE Since a reference solid with predominantly dispersive interactions is used it can be assumed that the dispersive fraction of the surface tension of the liquid can be determined from a single contact angle value.
6.4 Determination of the contact angle of the liquid to be tested on the reference solid Clean, dry, and condition the reference solid in accordance with ISO 19403-2. Measure the contact angle between the reference solid and the liquid to be tested in accordance with ISO 19403-2. Use at least ten drops for this. Use the same method (static or dynamic) as in 6.3 for measurement the contact angle.
7 Evaluation
7.1 General The standard deviations should not exceed the following values:
For the surface tension of the tested surface: ± 1 %.
For the surface free energy of the reference solid: preferably 0,3 mJ/m 2 , not exceeding 0,5 mJ/m 2 .
For the contact angles of the tested liquid on the reference solid: for the static method 1° and for the dynamic method 3°.
7.2 Owens-Wendt-Rabel-Kaelble method (OWRK method)
For reference surfaces with a surface free energy > 20 mJ/m 2 calculate the dispersive fraction of the surface tension of the liquid d l σ in accordance with equation (1):
Where
is the mean value of the measured contact angles between the tested liquid and the reference solid;
σ is the surface tension of the tested liquid, measured in accordance with 6.2;
σ is the surface free energy of the reference solid, measured in accordance with 6.3.
8 Precision
Information on precision is not yet available at present.
9 Test report
The test report shall contain at least the following information:
a) all details necessary to identify the tested product;
b) a reference to this standard (ISO 19403-5);
c) the surface tension of the liquid to be tested including all information in accordance with the test report of the method used;
d) the surface free energy of the reference solid including all information in accordance with the test report of the method used or reference and material and manufacturer, cleaning and preparation method of the
reference solid, if applicable;
e) for the determination of the polar and dispersive fractions of the surface tension of the liquid:
1) the information on whether it was measured statically or dynamically,
2) the used drop volumes or volume range and dosing speed,
3) the method with which the contact angle of the drop was obtained,BS ISO 19403-5 pdf download.