ISO 787-14:2019 pdf free.General methods of test for pigments and extenders一Determination of resistivity of aqueous extract.
7 Preparation of the conductivity meter
‘I’he conductivity meter and the conductivity cell are calibrated using a suitable conductivity calibration solution. In case of insufficient congruence of equipment display and calibration record, the measuring equipment shall he adjusted by correcting the cell constant IC.
8 Procedure
An aqueous extract of a pigment suspension shall be prepared before performing the conductivity measurement.
The water-wettability of the pigment shall be tested beforehand. In case of low wettability, the pigment shall he wetted using as much ethanol as necessary to obtain a soft paste. This paste is subsequently transferred into a suspension by adding water.
The pigment concentration of the suspension shall he adjusted in the range of 5 % to 10 % (mass
fraction).
For the extraction, the suspension shall be heated up. The heating time depends on the temperature applied: 100 °C for 5 mm, 60 °C for at least 30 mm. For homogenization, the suspension shall be stirred or shaken continuously. A cold extraction at room temperature is also possible. If used, this should he Included in the test report with the extraction duration.
Loss of mass during the warm extraction shall be adjusted by adding water to keep the pigment concentration at a constant level.
Filter the suspension after tempering through a fine textured filter paper (5.2). Separation of solid content may also be done by a centrifuge using clean test-glasses. In this case, the overlaying liquid is to be filtered through a filter paper by decanting.
For performing the measurement, fill the obtained filtrate into the cylinder (5.3) and place the conductivity ccli in it. Move the cell slowly up and down to remove all air bubbles.
The temperature of determination should preferably be 23 °C but a different temperature may he agreed between the parties provided that the necessary corrections are made to take account of the differences in temperature. Other measuring temperatures shall be reported.
Adjust the temperature slowly to 23 °C. The measuring cell shall be adjusted upright in the middle of the cylinder, the measuring opening (vent) around 10 mm below the surface of the liquid. Subsequently, the measurement can be started at (2 3,0 ± 0,5) °C.
In case the conductivity of the water applied without pigment and after being flown through the filter is larger than that given in 4.1, this result is used as blank value. The result of the conductivity measurement is then given by the difference of the conductivity of the filtrate and the water (blank value). The resistivity is the reciprocal value of the conductivity.
9 Expression of results
The result of the measurement is reported as electric resistivity in ohm metres (Ω●m) or as specific
electric conductivity in micro Siemens per centimetre (μS/cm), respectively, or in a unit of measurement derived from those.
10 Test report
The test report shall include the following information: a) all details necessary for complete identification of the product under test; b) a reference to this document, i.e. ISO 787-14:2019;
c) whether the pigment was wetted with ethanol; d) the result of the test as indicated in Clause 9;
e) any deviation, by agreement or otherwise, from the test procedure described in this document;
f) the date of the test.ISO 787-14 pdf download.