ASTM D395:16 pdf free download – Standard Test Methods for Rubber Property- -Compression Set.
7.3 One laboratory did not run the Test Method A testing:
therefore, the precision for Test Method A is derived from four laboratories.
7.4 The Type 1 precision results are given in Table I and Table 2.
7.5 Bias—ln test method statistical terminology, bias is the difference between an average test value and the reference or true test property value Reference values do not exist for these test methods since the value or level of the test properly is exclusively defined by the test method. Bias, therefore, cannot be determined.
TEST METHOD A—COMPRESSION SET UNDER CONSTANT FORCE IN AIR
8. Apparatus
8. 1 Micromeier–—A micrometer, analog or digital, for inca— suring specimen thickness, in accordance with Practice D3767, Method Al.
8.2 Compression Device, consisting of a torce application spring and two parallel compression plates assembled by means of a frame or threaded bolt in such a manner that the device shall be portable and self-contained atler the force has been applied and that the parallelism of the plates shall be maintained. The force may be applied in accordance with either 8.2.1 or 8.2.2.
8.2. I cc,libraied Spring Force Application—The required force shall be applied by a screw mechanism for compressing a calibrated spring the proper amount. The spring shall be of properly heat-treated spring steel with ends ground and perpendicular to the longitudinal axis of the spring. A suitable compression device is shown in Fig. I. The spring shall conform to the following requirements:
8.2.1.1 The spring shall be calibrated at room temperature 23 ± 5°C (73.4 ± 9°F) by applying successive increments of force not exceeding 250 N (50 IbO and measuring the corresponding deflection to the nearest 0.2 mm (0.01 in.). The curve obtained by plotting the forces against the corresponding detlections shall have a slope of 70 ± 3.5 kN/m (400 ± 20 lhf/in.) at 1.8 kN (400 lhf). The slope is obtained by dividing the two forces above and below I .8 kN by the difference between the corresponding detlections.
8.2. 1.2 The original dimensions of the spring shall not change due to fatigue by more than 0.3 mm (0.01 in.) ater it has been mounted in the compression device, compressed under a force of 1.8 kN (400 lbf), and heated in the oven for one week at 70°C士2°C (158士3.6°F). In ordinary use, a weekly check of the dimensions shall show no greater change than this over a period of I year.
8.2.1.3 The minimum force required to close the spring (solid) shall be 2.4 kN (530 lbf).