Significance and Use
This practice is important because producers of chromogenic glazings cannot wait for real-time in-service use to assess the product lifetime. Thus, a procedure is needed to estimate failure times based on accelerated weathering and related factors and tests. This practice does not provide guidance for how to follow the steps outlined as follows, but it provides as much information as is practical in an ASTM practice.
1.1 This practice is intended to provide guidance to architects, specifiers, manufacturers, and other parties who have an interest in evaluating the service life of chromogenic glazings.
1.2 This practice is intended to cover the main factors about service life that must be considered when evaluating glazings for performance until the failure time is reached. However, users of this practice must be aware that other factors must be considered, such as the effect of the interaction of materials, the use of the glazings, and to the environment in which a chromogenic glazing is exposed over its service life. Users of this practice are specifically cautioned to be aware that failure of the plastic polyurethane thermal barrier in an aluminum window containing a chromogenic blazing can cause a spreading or outward rotation of the glazing leges, called "hinging" or "clamming," which reduces the edge pressure on an insulated glazing (IG) unit, causing edge seal failure of the IG unit and allowing water to enter the IG unit and the glazing pocket.
1.3 The test methods referenced herein are laboratory tests conducted under specified conditions. These test methods are intended to simulate and, in some cases, to also accelerate actual in-service use of the chromogenic glazings. Results from these test methods cannot be used to predict the performance with time of units in the field unless actual corresponding field tests have been conducted and appropriate analyses have been conducted to show performance can be predicted from accelerated aging test methods.