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The effect of the viscoelastic properties of the edge seal on the moisture ingress into an insulating glass unit



Title: The effect of the viscoelastic properties of the edge seal on the moisture ingress into an insulating glass unit
Author(s): F. Verbeke, A. T. Wolf
Paper category : conference
Book title: International RILEM Symposium on Building Joint Sealants
Editor(s): A.T. Wolf
Print-ISBN: None
e-ISBN: 235158015X
Publisher: RILEM Publications SARL
Publication year: 1998
Pages: 218 - 236
Total Pages: 19
Nb references: 17
Language: English


Abstract: Late 1984, the German Institute for Window Technology (IFT) at Rosenheim published a study on the behaviour of insulating glass units. After defining the most influential conditions affecting the insulating glass unit, the report concluded unequivocally that insulating glass will and does fail (fog) by adhesion loss of its secondary seal. In this, the Rosenheim institute came to the same conclusions as already postulated by L. Strecker in his article published in 1978.
The present study investigated the reasons why and the mechanisms how the adhesion and the visco-elastic properties of the various sealants used as edge seal are altered long term and lead to the already mentioned insulating glass unit failure. Factors such as production defects and defective installation conditions do take their toll.
But the environmental influences, either considered alone or operating in synergy are of much higher interest on the visco-elastic properties of the edge seal.
This study showed that the glass adhesion of organic sealants deteriorates on UVageing, especially in synergy with a high humidity environment. Water uptake of the sealant leads to swelling of the edge seal and to a widening of the primary barrier seal. Furthermore, the water incorporated into the sealant acts as a plasticiser, which gives rise to a low modulus and thus to higher movements in the edge seal upon deflection of the glass panes. On the other hand, some environmental factors, such as heat, will lead to an embrittlement of the edge seal.
As a conclusion, this study showed that the moisture vapour transmission rate in the secondary sealant, as measured by the membrane technique, does not allow for predictive unit performance calculations. Only when combining the new concept of unit moisture vapour transmission rate with a sound understanding of the long term visco-elastic properties behaviour of the edge sealant, can one attempt to make valuable unit life predictive considerations.


Online publication: 2003-05-25
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/235158015X.016