This type of interlayer can experience delamination and a couple of examples of this are shown in the two photographs below.
The photographs show double glazed units which are part of a unitised curtain wall.
Summarising what can be seen in the photographs:
- In Photo 1, the left-hand unit has delamination that has penetrated about 30 mm into the glass panel showing a characteristic finger pattern of separation between the glass of the interlayer.
- In Photo 1, the right-hand unit has delamination with a milky appearance which indicates that water had been absorbed into the interlayer after delamination has occurred.
- In Photo 2 the right-hand panel has an area of complete delamination extending about 300 mm into the laminated pane with fingers at the edge where the delamination is just starting.
Delamination as shown in these photographs cannot be eliminated but it can be slowed down or virtually stopped from progressing by remedial measures, which if carefully chosen can also cover over the delamination and thus improve appearance. The main objective was to protect the glass as far as possible against any further contact with water.
It was important in the case shown above to maintain the movement capability between unitised panels and so simply sealing over the gaskets or providing a cover strip bonded to the glass to exclude water, was not acceptable. Various solutions were considered, and the final solution chosen was a very simple one, which was to bond the gaskets to the front leaf of the laminated glass, thus greatly reducing any further water contact with the PVB.
Good design can eliminate this problem by maintaining a fast-drying environment around laminated glass if it is subject to the weather. The alternative is to ensure the edges remain dry.