【国外标准】 Standard Test Method for Environmental Stress Crack Resistance (ESCR) of Threaded Plastic Closures

5.1 This test method compares closures for ESCR. Suitable variables are: closure materials, closure designs, processes, applied torque, and stress-crack agents.5.2 Results can be used for estimating shelf life of closures in terms of ESCR. This requires that the user has calibrated failure time in this test to failure time in the field for actual packaging systems.1.1 This test method determines the susceptibility of threaded plastic closures to failure due to environmental stress cracking (ESC).1.2 In use, threaded plastic closures can contact agents that appreciably reduce the stress at which cracks form. Examples of such agents are: soaps, detergents, oils, and liquid bleaches.1.3 Major factors that influence environmental stress crack resistance (ESCR) of threaded plastic closures include the closure material(s), closure design, molded-in stress, and applied stress.1.4 This procedure can be applied to all closures, but is particularly applicable to closures made from plastics based on polypropylene (PP) or polystyrene (PS).1.5 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8 and 6.2.NOTE 1: There is no known ISO equivalent to this standard.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.