ISO 527-1:2019 pdf free download – Plastics一Determination of tensile properties一 Part 1: General principles.
7.2 Dumb-bell specimens that break or slip inside the grips shall be discarded and further specimens shall be tested.
8 Conditioning
The test specimen shall be conditioned as specified in the appropriate standard for the material concerned. In the absence of this information, the most appropriate set of conditions from ISO 291 shall be selected and the conditioning time is at least 16 h, unless otherwise agreed upon by the interested parties, for example, for testing at elevated or low temperatures.
The preferred atmosphere is (23 ± 2) °C and (50 ± 10) % RH, except when the properties of the material are known to be insensitive to moisture, in which case humidity control is unnecessary.
9 Procedure
9.1 Test atmosphere
Conduct the test in the same atmosphere used for conditioning the test specimen, unless otherwise agreed upon by the interested parties, for example, for testing at elevated or low temperatures.
9.2 Dimensions of test specimen
9.2.1 Measure the width and the thickness of the test specimen (see 9.2.2), following the general guidance of ISO 16012 or ISO 23529, as applicable, within the limits indicated in Figure 3. to the nearest 0,1 mm for the width and to the nearest 0,01 mm for the thickness.
Avoid measuring the thickness at the edge of the specimen and directly in the centre (see NOTE). With rectangular or sharp tip faces the long side of the tip shall be parallel to the width direction when measuring thickness, and parallel to the thickness direction when measuring width.
NOTE This excludes the maximum and minimum thickness, which for injection moulded test specimens usually is found at the edge and in the centre, respectively. Injection moulded test specimens prepared according ISO 294-1, will generally have thickness differences due to sink marks of ih = hmax — hmin  0,1 mm (see Figure 3).
For injection-moulded test specimens, it is sufficient to determine the width and thickness within 5 mm midway between the shoulders.
9.2.2 In the case of injection-moulded specimens, obtained from multiple-cavity moulds, ensure that the dimensions of the specimens do not differ by more than ±0,2 5 % between cavities.
For test specimens cut from sheet or film material, it is permissible to assume that the mean width of the central parallel portion of the die is equivalent to the corresponding width of the specimen. The adoption of such a procedure should be based on comparative measurements taken at periodic intervals.
For the purposes of this document, the test specimen dimensions used for calculating tensile properties are measured at ambient temperature only. For the measurement of properties at other temperatures, therefore, the effects of thermal expansion are not taken into account.
9.3 Gripping
Place the test specimen in the grips, taking care to align the longitudinal axis of the test specimen with the axis of the testing machine. Tighten the grips evenly and firmly to avoid slippage of the test specimen and movement of the grips during the test. Gripping pressure shall not cause fracture or squashing of the test specimen (see NOTE 2).
NOTE 1 Stops can be used to facilitate alignment of the test specimen, especially in manual operation.
For gripping test specimens within a temperature chamber, it is recommended to close initially only one grip and to tighten the second one only after the temperature of the test specimen is equilibrated, unless the machine is capable of continuously reducing thermal stress if it arises.
NOTE 2 Fracture in the grips can happen, for example, when testing of specimens after heat aging. Squashing can occur in tests at elevated temperatures.
9.4 Prestresses
The specimen shall not be stressed substantially prior to testing. Such stresses can be generated during centring of a film specimen, or can be caused by the gripping pressure, especially with less rigid materials. They are, however, necessary to avoid a toe region at the start of the stress/strain diagram (see 5.1.3). The prestress a at the start of a test shall be positive but shall not exceed the following value.