# Dependency of QS-Value on Geographic Exposure Location

The changes of QS-value with exposure location can be approximated by Eq 3, in which the factor R provides a relative comparison between the specific ex­posure site and the central (reference) site. The relative comparison factor is calculated by dividing the QS-value of the specific exposure site by the QS-value of the central (reference) site as shown in Eq 4 and Fig. 6.

The equation of the central site derived for each sealant is given in Table 6, and the relative comparison factors of the specific exposure sites are shown in Fig. 7.

TABLE 6—Equation of each sealant at central site.

 Sealant Equation for QS(s • t) SR-2 QS(s• t) = (0• t10) X (1+0-є10) IB-2 QS(s • t) = (0.04• t4 0) X (1+2.2 • є0 5) MS-2(GP) QS(є • t) = (0.006 • t30) X (1+27.4• є0 3) MS-2(SR) QS(є • t) = (0.04 • t4 0) X (1+0.3 • є0 9) MS-1 QS(є • t) = (0.06 • t4 0) X (1 + 5.4 • є0 4) PS-2 QS(є • t) = (0.4 • t0 6) X (1 + 1.5 • є0 3) PU-2 QS(є • t) = (1.3 • t0 7) X (1+0.07 • є0 7) PU-1 QS(є • t) = (0.2 • t0 9) X (1 + 0.003 • є2 2) FIG. 7—Relative comparison factor for each sealant.

QS(e • t) = R X {(a • tb) X (1+c • ed)} (3)

where R is the relative comparison factor.

R = Average of QS-valUe[each site]/QS-valuecentral site] (4)

Relationship between Observation and Calculation

The relationship between observed QS-values and those calculated are shown in Fig. 8.

Conclusions

The following conclusions can be drawn from this study:

1. The equation for the QS-value of each sealant shows a reasonable cor­relation between the experimental observation and the calculated value for each exposure site.

2. Although the one-part polyurethane sealant shows a dependency of the degradation on the location of the exposure site (which matches the commonly held opinion that degradation is affected by the exposure location), the surface degradation of the other sealants does not show many differences between exposure locations. North

 Central

 South

 PU-1  Exposure month

 • :Observation£ Calculation о :Calculation§ Observation

FIG. 8—Relationship between observation and calculation.