Evaluation of Degradation for Tested Sealants

Ratings of surface crazing according to ISO 4628 Paints and Varnishes—Evaluation of degradation of coatings—Designation of quantity and size of defects, and of intensity of uniform changes in appearance—Part 4: Assessment of degree of cracking as shown in Tables 1 and 2 were used for the numerical evaluation of surface cracking of sealants caused by natural or accelerated weathering [3].

Based on the quantification of generated surface cracks, we used the product of quantity (Q) and size

(S) of surface cracks, termed “degree of degradation” (DoD), as the indicator of degradation induced by weathering, as shown in Eq. 1 below.

Degree of degradation (DoD) = Quantity (Q) X Size (.S’) (1)

In Table 3, the approximate relationship between the degree of degradation indicator (DoD) and the state of degradation (crazing) is shown.

TABLE і—Rating scheme for designating the quantity of cracks.

Rating

Quantity of cracks, Q

0

None, i. e., no detectable cracks

Very few, i. e.. some just significant cracks

2

Few, i, e., small but significant amount of cracks

3

Moderate, i. e., medium amount of cracks

4

Considerable, i. e., serious amount of cracks

5

Dense, i. e., dense pattern of cracks

TABLE 2—Rating scheme for designating the size of cracks.

Rating

Size of cracks, S

0

Not visible under ХЦ) magnification

1

Only visible under magnification up to X10

2

Just visible with normal corrected vision

3

Clearly visible with normal corrected vision

4

Large cracks generally up to 1 mm wide

5

Very large cracks generally more than 1 mm wide