Installation — business terrible  1 part
September 8th, 2015
The determination of the degradation by cracking and crazing was based on a 2 cm x 1 cm assessment area using the rating scheme provided in ISO 46284
[13] , with additional rating criteria introduced in order to determine the influence of minute cracks on the surface of sealants (see Table 4 and Fig. 4). The degree of degradation (QS) was based on the product of the rating for the quantity (Q) and size (S) of cracks as provided in Eq 1
QSit) = Q(t)x S(t) (1)
TABLE 4—Crack rating index.
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where:
QS(t) = QSvalue after t months,
Q(t) = rating Q after t months, and S(t) = rating of S after t months.
The approximate relationship between the QSvalue and the surface condition is indicated in Fig. 5. A QSvalue above about 20 indicates considerable degradation by surface cracks, and a QSvalue below 10 indicates few and smaller cracks. The relationship between the QSvalue and the cracking portion analyzed by the binary imaging showed a reasonable correlation [6].
An outline of the modeling of the QSvalue with weathering is indicated below [14]. For the modeling, the outdoor exposure test in Yamanashi Prefecture was carried out on sealant set 1 according to the conditions given in Table 5, and the QSvalue for the different extension/compression amplitudes along the central axis of the test specimens was determined over time.
The change of the QSvalue over time for the different movement exposures is given in Fig. 6, and the following conclusions can be drawn:
(1) For some sealants (MS2 (SR), PU1, and PU2), the QSvalue increases with the passage of time even when the test specimens are exposed to outdoor weathering in a static position (no forced movement). For
FIG. 5—Relationship of QSvalue and surface conditions.
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TABLE 5—’Weather summary ofYamanashi Prefecture, set 1.
*Term: Jan. 16, 2003, through Jan. 16, 2007. 
these sealants, forced movement (even at the small amplitude of ±1.5%) substantially accelerates the occurrence and worsens the degree of surface degradation.
(2) For all sealants (with the exception of SR2), surface degradation occurs when the specimens are exposed to dynamic conditions (forced movement plus outdoor weathering). For some of these sealants, higher movement amplitudes worsen or accelerate the surface degradation.
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FIG. 8—Relationship of QSvalue between observation and calculation.
The change in the QSvalue is then modeled as indicated in the steps below (see also Fig. 7).
• The QSvalue is plotted for each material and exposure condition along the zaxis, with the progress of time being on the xaxis and the exten – sion/compression amplitude on the yaxis.
• The measured QSvalues are fitted by a smooth line for every amplitude and exposure period.
• The curved surface then represents a threedimensional model (response surface) of the QSvalue as a function of the exposure time and amplitude of extension and compression exposure.
The QSvalue change can be calculated according to Eq 2
QS(s • t) = (a • tb)x(1 + c • sd) (2)
where:
QS(e • t) = QSvalue for an extension/compression ratio e (in %) after t months,
t = exposure time (in months),
e = extension/compression amplitude (as a percentage of joint with), and
a, b, c, and d = constants specific for each sealant.
In Eq 2, (a • tb) represents the QSvalue under static conditions (without extension/compression movement) after t months, and (1 + c • ed) represents the acceleration effect caused by the joint movement.
The congruity between the calculated and observed QSvalues is shown in Fig. 8, with the symbols ° and • indicating a gap between the two values and the c indicating identical values. The curvefit achieved with Eq 2 for the QSvalue of each product provides a reasonable relationship between observation and calculation over the exposure period of this test program. The equation derived for each sealant is given in Table 6. Because the silicone sealant SR2 did not show any surface degradation, the constants a and c equal 0, whereas for all other products these constants are greater than 0.
TABLE 6—Equations for each sealant.

Relationship between Outdoor and Accelerated Exposure
Sealants and Test Procedure
Accelerated artificial weathering exposure test and outdoor natural exposure test at Choshicity were carried out on the sealant set 2.