ISO 5794-1:2010 pdf free download – Rubber compounding ingredients – Silica, precipitated, hydrated一 Part 1: Non-rubber tests.
D.1 Principle
Two flasks of equal volume — one containing the test portion, the other empty — are filled with nitrogen under atmospheric pressure at room temperature. Both flasks are then cooled by immersion in liquid nitrogen.
At this temperature, the test portion adsorbs nitrogen, whereby a pressure difference is created between the flask containing the test portion and the reference flask. The pressure difference is measured by means of a differential pressure gauge. The specific surface area is calculated from the measured pressure difference, the nitrogen-gas feed pressure and the mass of the test portion. The method is similar to that described in ISO 4652-1:1994, Clause 4 (method B).
WARNING — All recognized health and safety precautions should be taken when performing this method of analysis.
D.2 Materials
D.2.1 Nitrogen gas, in a cylinder, or other source of pre-purified nitrogen, of recognized analytical quality.
D.2.2 Liquid nitrogen.
D.3 Apparatus
D.3.1 Adsorption apparatus1) (see Figure D.1), comprising a reference flask (G) and a sample flask (H) mounted with gastight connections. These connections are provided with one valve each (A and B) by means of which the flasks can be connected to the atmosphere. The gas to be adsorbed is fed into each flask through the connection pieces.
The flasks are made of glass which is resistant to sudden changes of temperature, and have a volume of approximately 100 cm3. The volume difference between the two flasks shall not exceed 0,1 %. The flask necks are made of calibrated precision glass tubing with an inside diameter of 5 mm ± 0,02 mm. This ensures that several flasks can be used as sample or reference flasks without having to adjust the compensation volume for each different combination.
A U-tube is mounted between the two flasks, and the arms of the pressure gauge are connected by capillary tubes to the two adsorption flasks. By means of valve D, the two adsorption vessels can be either separated from one another or connected to one another via their capillary tubes. Using valve E, the two liquid arms of the differential pressure gauge can be separated or joined together. The measuring fluid is dibutyl phthalate.
The two arms of the differential pressure gauge are made of calibrated precision glass tubing with an inside diameter of 5 mm ± 0,02 mm. Therefore, any change in volume during gas adsorption can be sufficiently accurately calculated. The feed capillary to the sample flask, owing to its short length, is considered as a compensation volume which is adjusted during preparation of the equipment (see D.7).
1) A suitable adsorption apparatus is the Areameter, available from Juwe GmbH, Fuggerstr. 6, D-41352 Korschenbroich, Germany. This information is given for the convenience of users of this part of ISO 5794 and does not constitute an endorsement by ISO of the apparatus named. Other apparatus may be used provided it complies with the specified requirements.
The gas is introduced into the equipment through valve C. If valves A, B and D are open, the gas flows through both flasks. If valves A and D are closed, the reference flask is shut off and only the sample flask is purged with the gas.
When a measurement is made, only part of the volume enclosed by valves A, B and C is cooled to the measurement temperature by the liquid nitrogen. The remaining volume, which will be at or near room temperature, shall not be more than 10 % of the total volume. The connections to the adsorption flasks are therefore capillaries which almost completely fill the necks of the flasks. In this manner, the volume of gas at room temperature is kept to a minimum.
NOTE Procedures for commissioning new equipment and for carrying out checks are given in D.7.