BS EN ISO 4600:1998 pdf free download.PLASTICS – DETERMINATION OF ENVIRONMENTAL STRESS CRACKING (ESC) – BALL OR PIN IMPRESSION METHOD.
Environmental stress cracking is exhibited by many materials, including plastics. When a plastic material is stressed or strained in air below its yield point, stress cracking can occur after a period of time, which may be very long. These stresses may be internal or external, or a combination of both. Exposure to a chemical medium simultaneously with the same stress or strain may result in a dramatic shortening of the time to failure. This phenomenon is referred to as environmental stress cracking (ESC). The permissible long-term stress or strain may be reduced considerably by this phenomenon.
The cracks produced may penetrate completely through the thickness of the material, separating it into two or more pieces, or they may be arrested on reaching regions of lower stress or different material morphology.
By keeping all but one parameter constant, the influence of the variable parameter on ESC can be assessed. The main objective of ESC measurements is to determine the effect of chemical media (environment) on plastics (test specimens and articles). The measurements may also be used to evaluate the influence of the moulding conditions upon the quality of an article when the failure mode corresponds to that obtained in actual service, it may not be possible, however, to establish any direct correlation between the results of short-duration ESC measurements on test specimens and the actual service behaviour of articles, because the behaviour of the latter is likely to be more complex than that of test specimens.
This International Standard specifies methods for the determination of environmental stress cracking (ESC) of plastics by means of a constant-strain test.
The test is applicable to finished products and to test specimens, prepared by moulding and/or machining, and can be used for the assessment of both ESC of a plastic product or material exposed to different environments, and for the determination of ESC of different plastics materials exposed to a specific environment.
NOTE 1 An alternative method for the determination of environmental stress cracking by means of a constantstrain test is specified in ISO 4599. A method for the determination of environmental stress cracking by means of a constant-stress test is specified in ISO 6252.BS EN ISO 4600:1998 pdf free download.