BS ISO 1853:2011 pdf download – Conducting and dissipative rubbers, vulcanized or thermoplastic — Measurement of resistivity
3.5 Expression of results
Average the three measurements of resistance for each test piece and calculate the resistivity, ρ , in Ω⋅m, as follows:
V is the measured potential, in V;
w is the width of the test piece, in m;
t is the thickness of the test piece, in m;
l is the distance between the potentiometer electrodes, in m;
I is measured current, in A.
Report the median value of the resistivities of the three test pieces.
3.6 Test report
The test report shall include the following information:
a) sample details:
1) a full description of the sample and its origin,
2) the method of preparation of the test piece from the sample, for example moulded or cut;
b) test method:
1) a full reference to the test method used, i.e. ISO 1853:2011, method 1,
2) the dimensions of the test piece used;
c) test details:
1) the time, temperature and humidity of conditioning prior to the test,
2) the voltage applied to the current electrodes,
3) the current through the test piece,
4) details of any procedures not specifed in this International Standard;
d) test results:
1) the median value of the resistivities of the three test pieces,
2) the individual average resistivity value for each test piece, if required;
e) the date of the test.
4 Method 2
4.1 Apparatus and materials
4.1.1 Brass electrodes, with dimensions as given in Table 1 and Figure 3. These may be either made of solid brass or brass-plated.
4.1.2 Mould, suitable for use with brass electrodes.
4.1.3 Sheets of insulating material, with a volume resistivity greater than 10 13 Ω⋅m and a surface resistivity greater than 10 14 Ω.
4.1.4 Oven, capable of being controlled at (70 ± 2) °C.
4.1.5 Resistance-measuring instrument: Any suitable resistance-measuring instrument which does not dissipate more than 0,25 W in the test piece.
4.2 Test piece Each test piece shall be a rectangular strip of rubber bonded during moulding to brass electrodes, with the dimensions given in Table 1 and shown in Figure 3. Either clean the brass electrodes in dilute nitric acid, wash with distilled water and allow to dry, or clean them with emery cloth. If brass-plated electrodes are used, ensure that the cleaning treatment does not remove the plating. Do not apply cements or rubber solutions to the brass or rubber, as these could affect the electrical resistance. When moulding the test pieces, ensure that the state of cure is similar to that of the product for which the compound is to be used. Ensure also that the rubber blanks placed in the mould are of such mass and dimensions as to give the minimum amount of fow and spew in moulding, the spew being of even thickness all round the test piece. Wherever possible, any grain in the material shall run along the length of each test piece. Remove each test piece from the mould with the minimum of bending and fexing. Remove any adhering spew from the electrodes, taking care not to buff or abrade the test piece, and ensure that the electrodes present a clean surface to the test leads. Reject any test piece showing evidence of insuffcient mould flling, poor adhesion to the electrodes or any other defect. Ensure that the surfaces of each test piece are clean by rubbing, where necessary, with Fuller’s earth and water, washing with distilled water and allowing to dry. Do not clean the test pieces with organic materials which would attack or swell the rubber. NOTE Bonding to brass is more easily achieved with conventional vulcanized rubber and might not be successful with thermoplastic rubbers.
4.3 Number of test pieces Three test pieces shall be prepared and tested.
4.4 Procedure Allow the test piece to rest for not less than 16 h after vulcanization or moulding, in accordance with ISO 23529. Place each test piece on one of the sheets of insulating material and heat in the oven for 2 h ± 15 min at a temperature of (70 ± 2) °C, to minimize the effects of strain caused by any previous treatment. Allow to cool and condition at standard laboratory temperature and humidity in accordance with ISO 23529 for not less than 16 h. Do not strain the test pieces after heating and before the test has been completed. After conditioning each test piece, and without removing it from its sheet of insulating material, measure, using the resistance-measuring instrument, the resistance between the bonded electrodes of each test piece in turn at the same standard temperature and humidity as was used to condition the test pieces.