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Durability of Sealants: A Question of Formulation and not of the Polymer Base
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Comparisons concerning the durability of sealants are often made by focusing on different polymer backbones such as silicones versus polyurethanes or silane-modified polymers. At first sight, this approach seems to give a clear and coherent picture of all products and types of polymers. On closer inspection, however, it becomes evident that varying formulations within one technology may have a much stronger influence on a product’s performance than switching from one technology to the other. Due to the availability of additives such as adhesion promoters, heat, and UV stabilizers and the like, two sealants with a similar chemical backbone can be formulated that differ greatly in performance. This enables chemists to formulate a wide range of sealants with the same polymer base. With the same or a similar polymer family, it is possible to formulate on the one hand a high-end sealant with, for example, superior weathering resistance and adhesion to nearly all substrates combined with a very high movement capability. On the other hand, it is possible to use a similar backbone to formulate a highly-filled sealant with a very high plasticizer content which can only accommodate very limited movements and which exhibits clear restrictions with regard to UV and weathering resistance. On the basis of several laboratory studies, the author will elaborate on the behaviour of different formulations and technologies regarding UV aging combined with cyclic movement as well as aesthetic aspects.
cyclic movement, sealant, polyurethane, silicone, silane-modified polymer
Sika, Services AG, Bad Urach,