ASTM D648, 1SO 75 Heat Deflection Temperature of Plastics Under Flexural Load in the Edgewise Position

ASTM D648 is a test method that determines the temperature of the deformation of specimens when they are subjected to a set of testing conditions. Read more about ASTM D648 Deflection Temperature of Plastics under Flexural Load in the Edgewise Position below.


Introduction to ASTM D648

ASTM D648 is a test method designed to measure the deflection temperature of plastics. The applications of the plastics are specified as per the results obtained. The fiber stress, method of loading, factors of time, and humidity contribute to the determination of the deflection temperature of plastics. The results obtained are specially used for quality control and specification purposes. The deflection temperature is a measure of a polymer’s ability to bear a given load at elevated temperatures. The deflection temperature is the temperature at which a test bar, loaded to the specified bending stress, deflects by 0.010 inch or 0.25 mm. The deflection temperature is also known as the ‘heat deflection temperature’, ‘deflection temperature under load’ (DTUL), or ‘heat distortion temperature’ (HDT). ASTM D648 test method is the common test method whereas ISO 75 is the analogous method. The test using a 1.8 MPa load is performed under ISO 75 Method A while the test using a 0.46 MPa load is performed under ISO 75 Method B.

ASTM D648 test method is generally applicable to both semi-rigid and rigid materials. The method is important for making recommendations about the use of the material in developmental work and provides information about short-term heat resistance. It also differentiates between materials that are able to sustain loads at high temperatures and those that lose rigidity over a narrow temperature range. 

ASTM D648 Thermal Deformation Tester

ASTM D648 Test Method

This test method proceeds by testing the rectangular bar in the edgewise position as a simple beam with the load applied at its center to give maximum fiber stresses. The specimen is immersed under the load in a heat transfer medium at a raised temperature. The test bar begins to deflect by 0.25 mm after some time has passed. The temperature of the medium at this point is recorded as the deflection temperature under the flexural load of the test specimen. 

Specimen settingThe specimens are measured and positioned edgewise in the apparatus such that the direction of the testing force is perpendicular to the direction of the molding flow. The sensitive part of the temperature measuring device is positioned close to the specimen without touching it. 
Application of loadThe load is applied to the specimen and it is lowered into the bath. The value of the desired stress is achieved by adjusting the load. The deflection measuring device is used to detect the deflection and the temperature of the liquid heat transfer medium at which the specimen deflects is recorded.

ASTM D648 Specimens

Specimen detailsASTM D648 specimens must be molded samples or sheet materials that are solid and rectangular.
Specimen dimensionsThe general sample thickness for ASTM D648 is 3 mm.
Specimen preparationSpecimens are injection molded or cut from molded or extruded sheets or plates. 

ASTM D648 Results

This test method evaluates the deflection properties of plastics along with the determination of the temperature at the specified load and deflection. 

Tests related to ASTM D648
ISO 75 is similar to ASTM D648. As per ISO 75, the bars are placed under the deflection measuring device. A load of 0.45 MPa or 1.80 MPa is placed on each specimen. The specimens are then lowered into a silicone oil bath where the temperature is raised at 2 °C per minute until they deflect 0.32 mm for ISO flat-wise, and 0.34 mm for ISO edgewise. ISO edgewise testing uses a bar 120 mm x 10 mm x 4 mm. ISO flat-wise testing uses a bar 80 mm x 10 mm x 4 mm.

Direct link for download ASTM D648 PDF


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Where can I get the astm d648 tested?

You can share your astm d648 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d648 test to various testing techniques.

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