ASTM D1693-01 pdf free download.Standard Test Method for Environmental Stress-Cracking of Ethylene Plastics.
1.1 This test method covers the determination of the susceptibility of ethylene plastics. as defined in Terminology D 883, to environmental stress-cracking when subjected to the conditions herein specified. Under certain conditions of stress and in the presence of environments such as soaps, wetting agents. oils, or detergents, ethylene plastics may exhibit mechanical failure by cracking.
1.2 The values stated in SI units are to be regarded as the standard.
3. Terminology
3. 1 Definitions:
3.1.1 stress-crack, n—an external or internal rupture in a plastic caused by tensile stresses less than its short-time mechanical strength.
3.1.1.1 Discussion—The development of such cracks is frequently accelerated by the environment to which the plastic is exposed. The stresses which cause cracking may be present internally or externally, or may be a combination of these stresses. The appearance of a network of fine cracks is called crazing.
3.1.2 stress-crack failure, n—for purposes of this test method, any crack visible to an observer with normal eyesight shall be interpreted as a failure of the entire specimen (1). Extension of the controlled imperfection shall not he construed as a failure. The appearance of more than one crack in a single specimen shall be construed as a single failure.
3. 1.2.1 Discussion—Cracks generally develop at the controlled imperfection and run to the outer edge of the specimen approximately at right angles to it (2). The cracks need not extend completely through the specimen to constitute failure. Cracks sometimes develop under the polymer surface, nianifesting themselves as depressions on the surface. The time when this occurs should he noted, and if the depression later develops into a crack, the time of dimpling should be considered as the failure time.
4. Summary of Test Method
4.1 Bent specimens of the plastic, each having a controlled imperfection on one surface, are exposed to the action of a surface-active agent. The proportion of the total number of specimens that crack in a given time is observed.
5. Signitlcance and Use
5.1 This test method may he used for routine inspection purposes by subjecting a required number of specimens to the test conditions for a specified time and noting the number that fail. The cracking obtained with the test reagent is indicative of what may be expected from a wide variety of surface-active agents. soaps, and organic substances that are not absorbed appreciably by the polymer.
5.2 Environmental stress-cracking is a property that is highly dependent upon the nature and level of the stresses applied and on the thermal history of the specimen (1). Under the conditions of the test method, high local multiaxial stresses are developed through the introduction of a controlled imperfection (23). Environmental stress-cracking has been found to occur most readily under such conditions.ASTM D1693 pd fdownload.