【国外标准】 Standard Test Method for Outdoor Weathering Exposure of Crosslinked Polyethylene (PEX) Tubing

5.1 During shipment, storage and installation, PEX tubing may be exposed to UV radiation prior to being shielded from further exposure after installation. The effects of UV exposure on PEX tubing is determined by use of this test method. By first exposing specimens to solar UV radiation and subsequently testing specimens for oxidative resistance or stabilizer functionality, changes as a result of solar UV radiation exposure can be evaluated. This information can be used to determine the maximum allowable total UV exposure prior to permanent shielding provided by installation.5.2 The results of short-term exposure tests can provide an indication of relative outdoor performance, but they should not be used to predict the absolute long-term performance of a material. The results of tests conducted for less than twelve months will depend on the particular season of the year in which they begin.1.1 This test method describes the procedure for exposing crosslinked polyethylene (PEX) tubing produced in accordance with Specification F876 to natural (sunlight) ultraviolet (UV) radiation and evaluating the effects of the exposure. This test method outlines the requirements for specimen size and preparation, exposure orientation, minimum UV exposure energy, post exposure testing and reporting.NOTE 1: While other laboratory UV exposure systems are available, this test method relies on natural sunlight as the UV radiation source. Laboratory methods may be added in the future if testing confirms a correlation between natural sunlight and laboratory exposure.1.2 PEX tubing is not designed for outdoor use. Data from short-term exposure testing per this test method can be used to judge the relative performance of PEX tubing stored outdoors for short periods of time prior to installation completely shielded from sunlight.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 The following precautionary caveat pertains only to the test method and post exposure testing portions, Sections 8 and 9 of this test method. 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.1.5 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.