AATCC 84-2000 Electrical Resistance of Yarns.
6. Test Specimens
6.1 The length of the test specimens depends on whether or not the electrodes used are in fixed or variable position. If the electrode system used provides for variable distances between the parallel plates, run a preliminary test to determine what distance between the plates provides the greatest sensitivity for resistance measurements for the meter being used.
6.2 To determine the uniformity of resistance along a single end of yarn, make measurements on at least 10 specimens of single strands.
6.3 For predicting the properties of woven or knitted fabrics to be made from yarn tested by this method, measurements should be made on multiple strands.
6.4 Prepare a minimum of three test specimens for each test, with parallel strands having the same tension, evenly spaced, with no overlap or touching along their length. When a limited supply of yarn is available, each specimen should contain 10 strands. If an adequate supply of yarn is available, prepare larger specimens by winding 50-100 turns on a skein winder, then fastening the strands with adhesive tape to prepare lengths suitable for the electrode system used. The number of strands in the specimen must be the same for each test specimen for reproducible results. The resistance may also be dependent on the cross-section of the yarn bundle; thus, similarly manufactured fibers may yield yarns with different resistance, due to different numbers of filaments in the yarn bundle or different numbers of plies.
7. Procedure
7.1 Calibrate the electrical resistance meter according to the manufacturer’s recommendations (see 11.3).
7.2 Condition the test specimens in a suitable testing chamber or conditioning room at the pre-selected relative humidity and temperature at which the electrical resistance of the yarn is to be measured.
7.2.1 For yarns which require antistatic treatments or whose electrostatic propen- sity is critical, measurements at 20% RH will be most meaningful. For special requirements other relative humidities may be used. For example, preconditioning at 21 ± 2°C is required for antistatic sheet- ing, film and textiles for use in hospital operating rooms (see 11.2.1). If it is necessary to measure electrical resistance under a broad range of conditions, additional tests may be run at 65% RH and at 24°C or other relevant conditions.
7.2.2 Condition the specimens at 24°C and at the predetermined relative humidity for a minimum of 4 h or until equilibrium is attained. A sufficient indication of equilibrium is no significant change of re- sistance on further conditioning. A significant change may be considered ± 5% of the logarithm of the resistance (Log R).
7.3 Remove static charges from the surface of the yarn by passing a radioactive bar over both sides of the specimen (see 11.4).
7.4 Place the yarn test specimen in firm contact with the electrodes with the direc- tion of the yarn perpendicular to the adja- cent edges of the electrodes. Apply sufficient tension to hold the strands straight.AATCC 84 pdf download.