Duration of Bonding - Chemically Bonded Composites

From investigations carried out by Wacker-Chemie GmbH it was found that bonding quality increases over time. Nonetheless, a bond cannot be guaranteed to last over a certain time under all possible circumstances. 

It is imperative for processors to apply sufficient testing to the bonding. Once a composite part is used under certain conditions where the function of the part essentially depends on the bonding force, sufficient testing of a prototype or a trial series is inevitable prior to use in the field. In many cases an enhanced ageing test under laboratory conditions will provide the solution. 

A viable solution could be the combination of primer and self-adhesive material, or even a combination between self-adhesive and mechanical anchorage. Mechanical anchorage will ensure a residual stability of the composite, and the self-adhesive material will guarantee hermetic sealing. 

In many other cases adhesion is only required until the assembly of a part. In this case a growth or loss of adhesion over time becomes irrelevant. 

Having mentioned the factors influencing the bond between the silicone rubber and the substrate and bearing in mind the vast number of possible material combinations the necessity of preliminary extensive tests for adhesion is obvious. 

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