BS ISO 37:2011 pdf download – Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties
9 Preparation of test pieces
9.1 Dumb-bells Dumb-bell test pieces shall be prepared by the appropriate methods described in ISO 23529. Dumb-bells shall, wherever possible, be cut parallel to the grain of the material unless grain effects are to be studied, in which case a set of dumb-bells shall also be cut perpendicular to the grain.
9.2 Rings Ring test pieces shall be prepared by cutting or punching, using the appropriate methods described in ISO 23529, or by moulding.
10 Conditioning of sample and test pieces
10.1 Time between vulcanization and testing For all test purposes, the minimum time between vulcanization and testing shall be 16 h. For non-product tests, the maximum time between vulcanization and testing shall be 4 weeks and, for evaluations intended to be comparable, the tests shall, as far as possible, be carried out after the same time interval. For product tests, whenever possible, the time between vulcanization and testing shall not exceed 3 months. In other cases, tests shall be made within 2 months of the date of receipt of the product by the customer.
10.2 Protection of samples and test pieces Samples and test pieces shall be protected as completely as possible from all external influences likely to cause damage during the interval between vulcanization and testing, e.g. they shall be protected from light and heat.
10.3 Conditioning of samples Condition all samples, other than those from latex, in accordance with ISO 23529 at a standard laboratory temperature, without humidity control, for not less than 3 h prior to cutting out the test pieces. Condition all prepared latex samples in accordance with ISO 23529 at a standard laboratory temperature, with humidity control, for not less than 96 h prior to cutting out the test pieces.
10.4 Conditioning of test pieces Condition all test pieces in accordance with ISO 23529. If the preparation of test pieces involves buffing, the interval between buffing and testing shall be not less than 16 h and not greater than 72 h. For tests at a standard laboratory temperature, test pieces that do not require further preparation may be tested immediately, if cut from conditioned test samples. Where additional preparation is involved, a minimum conditioning period of 3 h at standard laboratory temperature shall be allowed. For tests at temperatures other than a standard laboratory temperature, condition the test pieces at the temperature at which the test is to be conducted for a period sufficient to enable the test pieces to attain substantial equilibrium in accordance with ISO 23529 (see also 7.4.2).
11 Marking of dumb-bell test pieces If using a non-contact extensometer, mark the dumb-bell test pieces with two reference marks to define the test length as specified in Table 1, using a suitable marker. The test piece shall be unstrained when it is marked. The lines shall be marked on the narrow part of the test piece, as shown in Figure 2, i.e. equidistant from the centre of the test piece and at right angles to its longitudinal axis.
12 Measurement of test pieces
12.1 Dumb-bells Measure the thickness at the centre and at each end of the test length with the thickness gauge. Use the median value of the three measurements to calculate the area of the cross-section. In any one dumb-bell, none of the three thickness measurements of the narrow portion shall differ by more than 2 % from the median thickness. The width of the test piece shall be taken as the distance between the cutting edges of the die in the narrow part, and this distance shall be measured in accordance with ISO 23529 to the nearest 0,05 mm. Test pieces cut from products might have a non-rectangular cross-section, in which case the width shall be measured directly on the test piece.