ISO 34-2:2015 pdf download – Rubber, vulcanized or thermoplastic — Determination of tear strength — Part 2: Small (Delft) test pieces
4.3 Micrometer gauge, complying with the requirements of ISO 23529 and having a circular foot approximately 6 mm in diameter which exerts a pressure of 22 kPa ± 5 kPa. 4.4 Travelling microscope, giving at least 10× magnification, fitted with a graticule graduated at 0,01 mm intervals. 5 Calibration The requirements for calibration of the test apparatus are given in Annex B. 6 Test pieces 6.1 Shape and dimensions The test pieces shall be rectangular and shall conform to the dimensions shown in Figure 3 and Table 1. The test pieces shall be cut from a sheet by punching with the die (4.2), using a single blow of a mallet or (preferably) a single stroke of a press. The rubber may be wetted with water or a soap solution, and shall be supported on a sheet of slightly yielding material (for example leather, rubber belting or cardboard) on a flat, rigid surface. The tear strength is particularly susceptible to grain effects in the rubber. Normally, all test pieces are prepared with the grain at right angles to their length, but, in cases where grain effects are significant and are to be evaluated, two sets of test pieces shall be cut from the sheet, one at right angles to the grain and the other parallel to the grain. The thickness d of the test pieces shall be 2,0 mm ± 0,2 mm. 6.2 Measurement of dimensions 6.2.1 Measurement of thickness Measure the thickness of the test piece by ISO 23529:2010, method A. Take at least three gauge readings in the region of the slit. If an even number of readings is taken, use the average of the two median values as the result. If an odd number of readings is taken, use the median value. No reading shall deviate by more than 2 % from the value used. When the test results are to be used for comparative purposes, the thickness of any test piece shall not vary by more than 10 % from the mean thickness of all the test pieces.