ISO 3262-20 pdf download – Extenders for paints -Specifications and methods of test — Part 20: Fumed silica

ISO 3262-20 pdf download – Extenders for paints -Specifications and methods of test — Part 20: Fumed silica.
5 Sampling
Take a representative sample of the Product to be tested, as described in ISO 15528.
6 Determination of silica content
6.1 Principle
A test portion Is ignited, weighed and treated with sulfuric acid and hydrofluoric acid. The silicon letrafluoride thus formed is evaporated off and the sihca content is calculated from the resulting loss of mass
As me silica content is very high, a previous separation from the impurities is not required.
6.2 Reagents
Use only reagents of recognized analytical grade and only water of at least grade 3 purity as defined in ISO 3696.
6.2.1 Sulfuric acid, diluted I + 1.
Add 1 part by volume of concentrated sulfuric acid, approximately 96% (rn/rn), p 1,84 g/ml, slowly to I part by volume of water
6.2.2 Hydrofluoric acid, concentrated, approximately 40 %(mirn). p 1.13 g/ml.
6.3 Apparatus
Use orcnary laboratory apparatus and glassware, together with the following:
6.3.1 PlatInum dish.
6.3.2 Muffle furnace, capable of being maintained at (1 000 ± 20) C.
6.33 infrared evaporator.
6.3.4 DesIccator, containing magnesium perchlorate as desiccant.
6.4 Procedure
6.4.1 Number of determinations
Carry out the determination in dilicate.
6.4.2 Test portion
Weigh. to the nearest 0,2 mg. approximately 1 g (rn0) of the sample (see clause 5) into the tared platinum dish
(6.3.1).
6.4.3 Determination
i9nite the test portion in the muffle furnace (8.3.2) at (1000 ± 20) C to constant mass (this should take approximately 2 h) and allow to cool in the desiccator (6.3.4). Weigh the test porlion again (m1).
7.4.3 Calibration graph
Correct each ab6orbance by sitlracting the reading obtained from the blank matching solution and plot for each element a graph havrng the masses, in micrograms. of the element contained ii I ml of standard matching solution as abscissae and the corresponding values of the absorbance as ordinates,
7.4.4 Preparation of the test solution Carry out the determinations in duplicate.
Weigh, to the nearest 1 mg, approximately 5 g (in0) of the sample (see clause 5) into the platinum dish (7.3.3). Wet this test portion with 5 ml ol water for grade A turned silica and with 3 ml to 4 ml of ethanol (7.2.8) and 2 ml to 3 ml of water for gade B fumed silica.
Add 2 ml of sulfuric acid (7.2.1) and 30 ml of hydrolluoric acid (7.2.2) and evaporate carefully to a syrup. Then add a further 10 ml of hydrotluoric acid and evaporate to dryness. If the evaporation of the silicon tetrafluoride is not complete, add a further 10 ml of hy&ofluoric acid and evaporate again.
Heat the residue until white fumes are no longer evolved, then add 5 ml of hydrochloric acid (7.2.3) and 2 ml to3 ml of water and dissolve the residue.
Transfer the solution obtained to a 50 ml one-mark volumetric flask. For aluminium and titanium determinations by FAAS, add 2,5 ml of caesium chloride buffer solution (72.5). Then make up to 50 ml with water.
7.4.5 DetermInation of aluminium, titanium and iron
First adjust the spectrometer as descrted in 7.42.1 or 7.4.2.2 and measise the absorbance of the blank matching solution (see 7.4.1) in the spectrometer (7.3.1 or 7.3.2). Then measure the absorbance of the test solution (see 7.4,4) three times and, afterwards, that of the blank matching solution again. Finaly. redetermine the absorbance of the standard matching solution with the highest concentration in order to verify that the response of the apparatus has not changed.
If the absorbance of the test solution is higher than the absorbance of the standard matching solution with the highest concentration, dilute the test solution with a known volume of dilute hydrochloric acid (7.2.4). Note the dilution factor I),
7.4.6 DetermInation of the total loss on ignition
Carry out the determination in dtlicate.
Weigh. to the nearest 0,2 mg. approximately 1 g (in3) of the sample (see clause 5) into a platinum crucible (6.3.1).
NOTE Weighing out the test porlions tor the deterrnmation of the slica content (see 6 4.2) and the total loss on ignition may be camed cut at the same time.
Ignite the test portion to constant mass in a muffle furnace (6,32) (this shouki take approximately 2 h) at (1 000 ± 20) C and allow to cool in a desiccator (6.3.4). Weigh the ignited test portion to the nearest 0,2 mg (m4).
Calculate the total loss on ignition, expressed as a percentage by mass, using the equation.