ISO 9073-4:2021 pdf download – Nonwovens — Test methods — Part 4: Determination of tear resistance by the trapezoid procedure.
4 Principle Marking of a trapezoid on a test specimen. Clamping of the non-parallel sides of the trapezoid in the jaws of a tensile testing machine. Application of a continuously increasing extension to the test specimen in such a way that a tear propagates across its width. The force to continue the tear over a specified distance is recorded. The arithmetic mean of the maximum force of specimens is taken as the result of testing. 5 Apparatus 5.1 Tensile testing machine, metrological confirmation system of which shall be in accordance with ISO 10012.The constant rate of extension testing machine (CRE testing machine) having the following characteristics: a) capable of operating at a constant rate of extension of (100 ± 10) mm/min; b) capable of gauge length to be set to (25 ± 1) mm; c) provided with means for recording the force applied to the test specimen during the tear test; d) under conditions of use, accuracy of the apparatus shall be class 1 of ISO 7500-1. The error of the indicated or recorded maximum force at any point in the range in which the machine is used shall not exceed ± 1 %,and the error of the indicated or recorded jaw separation shall not exceed ± 1 mm; e) if recording of force and extension is obtained by means of data acquisition boards and software, the frequency of data collection shall be at least 8 per second. If a class 2 tensile testing machine according to ISO 7500-1 is to be used, this shall be stated in the test report. NOTE Constant rate of traverse type (CRT) tester can also be used when agreed upon between interested parties. There can be no overall correlation between the test results obtained with the CRT-type machine and CRE-type machine.
5.2 Clamping device, comprising the two jaws of the machine, the central points of which are in the line of applied force, the front edges at right angles to the line of applied force and the clamping faces in the same plane. The jaws shall be capable of holding the test specimen without allowing it to slip and designed so that they do not cut or otherwise weaken the test specimen. The width of the jaws should preferably be 100 mm, but shall not be less than the width of the test specimen. 5.3 Isosceles trapezoid template, having dimensions with a tolerance of ± 0,5 % as shown in Figure 1. 5.4 Equipment, in which test specimens can be immersed in water preparatory to wet testing. 5.5 Grade 3 water, in accordance with ISO 3696 for wetting test specimens. 5.6 Nonionic wetting agent.