Results

Table 4 summarizes the test results of the ASTM E2188-10 [6] weathering proto­col of the small IG units. During the test protocol the small IG units have the frost point and argon percentage measured initially, after 2 weeks of high tem­perature and humidity, after nine weeks of accelerated weathering (hot, cold, UV, and water spray) and after 4 weeks of high temperature and humidity. Each argon-percentage test point for a specific specimen is an average of five readings according to ASTM E2649 [15]. These averages are further averaged and plotted in Fig. 25.

All six of the control specimens qualified per ASTM E2190-10 [7], meaning that the frost points of the specimens remained below —90°F (—68°C) and the average argon retention of all the specimens was greater than 80 % On the other hand, the 50 %, 100 %, and 150 % samples did not meet the testing criteria. Six

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FIG. 20—Overlay of PIB in-plane displacements as measured in test 2 and obtained from numerical model.

specimens must meet the requirements described in Sec. 4 of ASTM E2190-10 but, because there were no available replacement specimens when a specimen broke during testing, the entire sample group could not be qualified. The reason for the limited number of specimens was because the research team did not strictly follow the requirements of the ASTM E2188 standard [6] and procure twelve total samples as put forth in Sec. 5.7. Had this been done, the broken specimens could have been replaced with a new one from the remaining speci­mens. Any lites that broke are noted in the table as “breakage" or “thermal break." The “breakage" label refers to breaks that occurred during the initial dis­placement of the specimens before the testing began. “Thermal Break" refers to lite failure that occurred during testing.

All of the 50 %, 100 %, and 150 % units that did not experience breakage showed frost points below —90°F (—68°C). Additionally, the average argon retention of these specimens was greater than 80 %

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FIG. 21—Dimensions of primary (PIB) and secondary (silicone) at control no bending.

An unforeseen result from the durability testing was the failure of the epoxy adhesive in tension. The test units used an epoxy adhesive in several locations. The epoxy was used to keep the small IG units attached into the steel frame. This epoxy held fast in all of the tests, however, the epoxy adhesive used to induce displacement in the Z direction adhesively released from the glass dur­ing the humidity and accelerated weathering cycles. Because the epoxy failed in all of the tests where tension was applied, this testing represented stressing the PIB in the Z direction for only a portion and not the entire test.

FIG. 22—Deformations of PIB and silicone at 50 %o or 4 in. (100mm) of bending.

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ENLARGED 0X

FIG. 23—Deformations of PIB and silicone at 100 % or8 in. (200 mm) ofbending.

The measurements that were taken to document the edge-seal displacement were monitored after the first high-humidity phase to ensure that the edge-seal strain was maintained. The measurements between the steel frame and the pane of glass that was adhered to it were maintained and no relative movement occurred between these two elements. The measured distance between the steel frame and the displaced piece of glass, however, increased by approximately

0. 005 in. (0.13 mm) from its initial value. All other measurements, including the

FIG. 25—% Argon within the test units as measured during the ASTM E2188-10 [6] testing protocol.

“z” displacements were maintained after the first high-humidity phase. It was during the weathering phase of testing that epoxy adhesive failure caused the tensioning mechanism to fail and release strain on the edge seal in the “z” direction.