ASTM D648:2006 pdf free download – Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position.
11. Conditioning
11 . 1 Conditioning—Condition the test specimens at 23 ± 2°C [73.4 ± 3.6°F] and 50 ± 5 % relative humidity for not less than 40 h prior to test in accordance with Procedure A of Practice D 618 unless otherwise specified in the material standard or contract between interested parties. In cases of disagreement, the tolerances shall be ± 1°C [1.8°F] and ±2 % relative humidity.
NOTE 9—Shorter conditioning periods may be used when it is shown that they do not affect the results of this lest. Longer conditioning Limes may be required for some materials that continue to change with time.
12. Procedure
12.1 Measure the width and depth of each specimen with a suitable micrometer (as described in 7.2) at several points along the span. Average these respective readings to obtain the nominal width and depth value for the specimen. These values are used to determine the amount of applied force necessary to produce the specified fiber stress in each specimen (see 7.1.4).
12.2 Position the test specimens edgewise in the apparatus and ensure that they are properly aligned on the supports so that the direction of the testing force is perpendicular to the direction of the molding flow. If the specimen support unit has metal clips or auxiliary supports on it to hold the specimen perpendicular to the load and to prevent the specimen from being displaced by the circulating oil, only one surface of the clip or auxiliary support may touch the specimen at any one time. The presence of any clip or auxiliary support shall not impede the deflection of the specimen or place additional force on the specimen that will result in more load having to be applied to achieve deflection.
NoTE 10—Holding of the specimens upright on the specimen supports by the use of clips or auxiliary supports that apply pressure to the specimen have been shown to alter the deflection [emperawre when testing at the 0.45 MPa Stress level.
12.3 The thermometer bulb or sensitive part of the temperature measuring device shall he positioned as close as possible to the test specimen (within 10 mm) without touching it. The stirring of the liquid-heat transfer medium shall he sufficient to ensure that temperature of the medium is within 1 .0°C at any point within 10 mm of the specimen. If stirring is not sufficient to meet the 1.0°C requirement, then the temperature measuring device shall be placed at the same level as the specimen and within 10 mm of the point at which the specimen is loaded.
12.4 Ascertain that the temperature of the bath is suitable. The bath temperature shall be at ambient temperature at the start of the test unless previous tests have shown that, for the particular material under test, no error is introduced by starting at a higher temperature.
12.5 Carefully apply the loaded rod to the specimen and lower the assembly into the bath.
12.6 Adjust the load so that the desired stress of 0.455 MPa [66 psi] or 1.82 MPa [264 psi] is obtained.