Weathering Test Procedure

The durability of the test specimens was evaluated by industry established and accepted methods of exposing the units to high humidity environment, alternat­ing temperatures and periods of ultraviolet (UV) exposure and water spray. The method chosen is described in detail in ASTM E2188-10 [6]. The procedure and the cyclical phase are shown in Fig. 12. Evaluation of argon retention was con­ducted per ASTM E2649 [15].

The test began by establishing an initial frost point per ASTM E546 [16]. The ASTM E546 test method placed a cold plate on the surface of the glass.

Condensation in the form of frost or, at higher temperatures, dew would be observed if there was sufficient moisture in the IG unit. Factory-made units are expected to demonstrate low-temperature frost points at the start of the test, because the desiccant is new and not subjected to any extreme environmental influences. Typically, the initial-frost-point results are expected to be lower than —90°F(-68° C).

Additionally, testing for Argon in the units was conducted per ASTM E2649 [15]. All units began the test with greater than 90 % argon concentration.

After these initial tests, the units were placed in a high humidity chamber for a period of 2 weeks. The chamber was maintained at 140°F (60°C) and 95 % relative humidity for the entire two weeks.

Once this phase was completed, the units were removed and allowed to equilibrate to standard temperatures and conditions for a period of 24 h. The units were then measured again for frost point and argon retention and the val­ues were recorded.

At the completion of the data collection, the units were placed in a weather­cycling phase. During this phase, the units experienced cold temperatures to —20°F (—29°C). After a hold period, they were allowed to return to standard temperatures at which point they are exposed to ultraviolet light and mist spray while their temperatures were raised to 140°F (60°C). The spray was turned off and after a hold at high temperature and while the ultraviolet light is still on, the units were allowed to return to standard temperatures where the cycle begins again. This 6-h cycle was repeated for 9 weeks.

At the completion of the weather cycling phase, the units were once again removed, allowed to equilibrate for 24 h and the frost-point and argon values were measured and recorded.

Finally, the units were placed back in the humidity chamber (as described above) for an additional 4 weeks. At the completion of the 4 weeks, they were removed, allowed to equilibrate for 24 h and the final frost-point and argon val­ues were taken and recorded.