BS EN ISO 3915:2022 pdf – Plastics — Measurement of resistivity of conductive plastics.
5.4 Electrometer, having an input resistance greater than 10 11 Ω and measuring to an accuracy of ±5 %. 5.5 Sheet of highly insulating material, having a volume resistivity greater than 10 15 Ω⋅cm. 5.6 Oven, capable of being maintained at a temperature of (70 ± 2) °C, or (60 ± 2) °C, if required. 6 Specimen The specimen shall be a strip of preferably 10 mm width. Higher widths may be used as long as they do not exceed the width of the potentiometric electrodes (see 5.3.2). The specimen shall be 70 mm to 150 mm long and shall normally be 3 mm to 4 mm thick with a tolerance on uniformity of thickness of ±5 %. Thicker or thinner specimens may be cut from sheets or products. Care shall be taken to avoid bending or stretching the sheets or specimens, especially when they are thinner than standard. The specimen may be cut with a knife or razor blade, but care shall be taken to minimize distortion as this can affect the resistance values. The surfaces of the specimen shall be clean; if necessary, they may be cleaned by rubbing with fuller’s earth (hydrated magnesium-aluminium silicate) and water, rinsing with distilled water and allowing to dry. 1) The surfaces shall neither be buffed nor abraded, nor shall they be cleaned with organic materials that attack or swell the material.
7 Number of specimens From each of two perpendicular directions, three specimens of equal size shall be prepared and tested. The two directions should, where possible, be chosen to be along and across any direction of flow during processing. 8 Procedure 8.1 After preparation, allow the specimen to remain at room temperature and ambient humidity conditions for at least 16 h. 8.2 Prior to the commencement of the test, connect the current electrodes (5.3.1) to the ends of the specimen, either by using the clamps or grips, or by covering the same area with conductive paint. 8.3 The required conditioning of the specimen should be described in the material specification. If this is not the case, the following procedure can be used: Immediately after applying the current electrodes, place the specimen on the sheet of highly insulating material (5.5) and heat in the oven (5.6) for 2 h at a temperature of (70 ± 2) °C to remove strains and irregularities caused by previous treatment. Cool for at least 1 h and test at (23 ± 2) °C and (50 ± 5) % relative humidity without disturbing the specimen. The specimen shall always be tested on the sheet of insulating material. With some materials, distortion can occur at 70 °C and heating for 5 h at (60 ± 2) °C can then be preferable. 8.4 Place the potentiometric electrode system (5.3.2) on the specimen, ensuring that the knife-edge contacts are at right angles to the direction of current flow and that neither potentiometric electrode is within 20 mm of a current electrode. Apply the current and measure the voltage drop between the potentiometric electrodes using the electrometer (5.4).
10 Test report The test report shall include the following particulars: a) a reference to this document, including its year of publication, i.e. ISO 3915; b) complete identification of the sample, including processing details if relevant; c) dimensions of the test specimen; d) conditioning, if different from that described in 8.3, or if the 60 °C conditioning is used; e) the width of and the distance between the potentiometric electrodes; f) the applied current and the average value of voltage drop measured; g) the individual resistivity values and the medians of the results in the two directions of test; h) any other details that can have had an effect on the test results; i) any deviations from the procedure; k) any unusual features observed; l) the date of the test.