Weathering and Forced Movement Exposure
The outdoor exposure to natural weathering was carried out in two locations in Central Japan, located within Yamanashi Prefecture (near Mount Fuji, west of Tokyo) and in Choshi City (near Narita International Airport, east of Tokyo). At both sites the specimens were exposed for a period of four years on weathering racks with an inclination angle of 30° to the horizontal and facing toward the south.
The test specimens in Yamanashi Prefecture were exposed both statically (i. e., without forced movement) and dynamically (i. e., with forced movement); during the exposure the extension/compression cycles were periodically reversed. Test specimens at the Choshi City site were exposed only dynamically. In an earlier study , the effect of the frequency of the extension/compression cycling on the sealants was studied. That study found only a rather small effect of the cycling frequency on the surface degradation of the sealant with the cycling frequency being set at seven times in a week, two times in a week, one time in a week, and one time in one month . For historical reasons, the extension and compression position was periodically reversed twice per week at the Yamanashi site and once per month at the Choshi site. Only later was it decided that a reversal of the extension/compression cycle once per month presented the best compromise between the degradation achieved and the work load required for handling the test specimens . Table 3 provides information on the weathering and exposure conditions at both exposure sites.
Accelerated weathering was carried out in automated exposure devices using three artificial light sources: filtered xenon arc, fluorescent ultraviolet lamps, and open flame carbon arc, as standardized in JIS A 1415  (similar to ISO 4892 [8-11]). The following legend is applied throughout this paper in order to expediently identify the different light sources: filtered xenon-arc, XWOM; open-flame carbon arc, SWOM; fluorescent ultraviolet, UV. Exposure to accelerated artificial weathering was carried out for a total period of 5000 h, with the
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extension and compression position periodically reversed every 500 h (note: the influence of the exchange interval in the accelerated weathering exposure is currently being considered within ISO/TC59/SC8/WG10 ).