ASTM D648-18 pdf download.Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position.
3. Terminology
3.1 General—The definitions of plastics used in this test method are in accordance with Terminology D883 unless otherwise indicated.
4. Summary of Test Method
4.1 A bar of rectangular cross section is tested in the edgewise position as a simple beam with the load applied at its center to give maximum fiber stresses of0.455 MPa (66 psi) or 1.82 MPa (264 psi) (Note 3). The specimen is immersed under load in a heat-transfer medium provided with a means of raising the temperature at 2 6 0.2°C/min. The temperature of the medium is measured when the test bar has deflected 0.25 mm (0.010 in.). This temperature is recorded as the deflection temperature under flexural load of the test specimen. N OTE 3—Around robin has been conducted that showed that there is no advantage to using higher loads when measuring deflection temperature of present-day plastics with present-day instruments.
5. Significance and Use
5.1 This test is particularly suited to control and develop- ment work. Data obtained by this test method may not be used to predict the behavior ofplastic materials at elevated tempera- tures except in applications in which the factors of time, temperature, method of loading, and fiber stress are similar to those specified in this test method. The data are not intended for use in design or predicting endurance at elevated tempera- tures.
6. Interferences
6.1 The results of the test may depend on the rate of heat transfer between the fluid and the specimen and the thermal conductivity of the fluid.
6.2 The results of this test may depend on the measured width and depth of the specimen and the final deflection at which the deflection temperature is determined.
6.3 The type of mold and the molding process used to produce test specimens affects the results obtained in this test. Molding conditions shall be in accordance with the standard for that material or shall be agreed upon by the cooperating laboratories. 6.4 Results of testing may be affected by the design of the test equipment. The test span (either 100 mm or 101.6 mm) will influence the resultant measurement. Instrumentation equipped with metal clips or other types of auxiliary supports designed to maintain specimens perpendicular to the applied load may affect the test results if the pressure is sufficient to restrict the downward motion of the specimen at its center.
7. Apparatus
7.1 The apparatus shall be constructed essentially as shown in Fig. 1 and shall consist of the following:
7.1.1 Specimen Supports, metal supports, allowing the load to be applied on top of the specimen vertically and midway between the supports, which shall be separated by a distance, defined in 7.1.1.1 or
7.1.1.2. The contact edges of the supports and of the piece by which load is applied shall be rounded to a radius of 3 6 0.2 mm (0.118 6 0.008 in.).
7.1.1.1 Method A—101.6 6 0.5 mm (4.0 6 0.02 in.).ASTM D648 pdf download.