Test Results

The changes in the QS-value for the different sealants are provided in Fig. 3. A summary of the test results is given below.

1. Although the degree of degradation increases with an increase in the extent of extension and compression, the degree to which this change occurs with an increasing extent of extension and compression de­pends on the type of sealant.

2. The two-part silicone sealants did not show surface degradation for any of the test conditions.

Discussion

Model of QS-Value Change

A three-dimensional model (response surface) of the QS-value as a function of exposure time and extent of extension and compression was generated from the test results as shown in Fig. 5.

Based on Fig. 6, the equation for the QS-value can be stated as shown in Eq

2.

image218

image219

FIG. 3—Change of QS-value of sealants.

QS value

State of Degradation

25

20

15

^ Serious Degradation

A CyyAsS Medium Degradation

10

r J Small Degradation

5

Slight Degradation

0

Little Degradation

FIG. 4—Surface degradation condition rating.

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FIG. 5—Response surface model of dependency of QS-value on exposure time and de­gree of extension/compression.

image221

FIG. 6—Model of QS-value change in each exposure site.

QS(s • t) = QS0(t) X B = (a • tb) X (1+ c • sd) (2)

where QS(s • t) is the QS-value at є % after t months, QSo(t) is the QS-value under static condition after t months, t is the exposure duration (in months), є is the extent of extension and compression ratio, and a, b, c, and d are con­stants.