BS ISO 1409:2020 pdf download.Plastics/rubber — Polymer dispersions and rubber latices (natural and synthetic) — Determination of surface tension.
4 Principle
4.1 Method A
Method A is suitable valid for polymer dispersions and rubber latices with a viscosity less than 200 mPa’s. To achieve this, the dispersion or latex is diluted with water to a mass fraction of total solids of 40 %. If necessary, the total solid content is further reduced to ensure that the viscosity is under the specified limit.
A horizontally suspended ring of thin wire is attached to a “Du Nouy type” tensiometer and immersed in the liquid under test, then slowly pulled out. just before the ring detaches itself from the surface of the liquid, the force required reaches a maximum. This force is measured by a torsion balance, inductive pick-up or some other suitable measuring device.
42 Method B
When a liquid is brought into contact with the edge of the plate which is suspended from the “Wilhelmy type” tensiometer, the plate is pulled down into the liquid due to the surface tension. The instrument applies an upward vertical force to the plate so that the plate reaches the force balance. This vertical force is measured and used to calculate the surface tension of the liquid.
5 Reagents
5.1 Distilled water, carbon-dioxide-free, or water of equivalent purity (grade 3 as defined in
ISO 3696).
5.2 Toluene, of recognized analytical purity.
6 Apparatus
6.1 Tensiometer (Du Nouy type), with a platinum or platinum-iridium alloy ring of either 60 mm or
40 mm nominal circumference (corresponding to 9,55 mm or 6,37 mm internal radius, respectively) and
made of wire having a nominal radius of 0,185 mm.
6.2 Tensiorneter (Wilhelmy type), with a flat, thin plate made of platinum or platinum-iridium alloy, and the size suitable for the tensiometer.
6.3 Glass dish or vessel, of 50 cm3 capacity, with an internal diameter of at least 45 mm or suitable for the thermostat of the tensiometer.
6.4 Thermostatic bath, or some other means of adjusting the temperature of the test sample to
23 °C ± 1 °C (27 °C ± 1 °C for tropical countries).
8.1.3.1 If the total solids content of the test sample of latex or polymer dispersion is not known, determine it in accordance with ISO 124. If the mass fraction of total solids is greater than 40 %, dilute the test sample to a mass fraction of total solids of 40 % ± 1 % with water (5.1). If it is suspected that the viscosity of the diluted test sample is still greater than 200 mPa·s, determine it by the appropriate method given in ISO 1652, ISO 2555 or ISO 3219. If necessary, dilute the test sample further until the viscosity is less than 200 mPa·s, noting the final total solids content. NOTE Dilution to a mass fraction of 40 % has a negligible effect on the surface tension of polymer dispersions and rubber latices. In some cases, the surface tension at a higher total solids content can be required, in which case this can be measured by the method as specified with little loss of accuracy, provided that the viscosity is less than 200 mPa⋅s. If the density of the diluted test sample of latex or polymer dispersion is not known, determine it in accordance with ISO 705.BS ISO 1409 pdf download.