scope:

This method covers the determination of the tensile properties of plastics in the form of standard dumbbell-shaped test specimens when tested under defined conditions of pretreatment, temperature, humidity, and testing machine speed.

This method can be used for testing materials of any thickness up to 14 mm (0.55 in.). However, for testing specimens in the form of thin sheeting, including film less than 1.0 mm (0.04 in.) in thickness ASTM Method D 882, Test for Tensile Properties of Thin Plastic Sheeting,² is the preferred method. Materials with a thickness greater than 14 mm (0.55 in.) must be reduced by machining.

NOTE 1-A complete metric companion to Method D 638 has been developed-D 638 M.

NOTE 2-This method is not intended to cover precise physical procedures. It is recognized that the constant-rate-of-crosshead-movement type of test leaves much to be desired from a theoretical standpoint, that wide differences may exist between rate of crosshead movement and rate of strain between gage marks on the specimen, and that the testing speeds specified disguise important effects characteristic of materials in the plastic state. Further, it is realized that variations in the thicknesses of test specimens, which are permitted by these procedures, produce variations in the surface-volume ratios of such specimens, and that these variations may influence the test results. Hence, where directly comparable results are desired, all samples should be of equal thickness. Special additional tests should be used where more precise physical data are needed.

NOTE 3-This method may be used for testing phenolic molded resin or laminated materials. However, where these materials are used as electrical insulation, such materials should be tested in accordance with ASTM Method D 229, Testing Rigid Sheet and Plate Materials Used for Electrical Insulation,² and ASTM Method D 651, Test for Tensile Strength of Molded Electrical Insulating Materials.³