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Sealants for Construction - Part III-2 Elastomeric, High Performances Sealants

SpecialChem / Philippe Cognard – May 26, 2004

In this section we will study the 4 chemical types of sealants which display elastomeric properties: * Polysulfide sealants, * Silicone sealants, * Polyurethane sealants, * MS Polymer sealants. These sealants may be considered as high performances sealants because they have high capabilities of movement, service elongation from 15 to 40 %. Polysulfide sealants These sealants have been developed in the sixties in USA by THIOKOL Corporation, and they were the first elastomeric sealants. With an average molecular weight of 4000. Curing agents were in the past mostly PbO2 for the 2 components sealants but since PbO2 is considered as a dangerous product it has been replaced by other catalysts. Anyway construction sealants are mostly one component formulation and the favorite curing agent is calcium peroxide. Curing: Curing proceeds by converting the -SH termination into disulfide bonds. This is achieved by oxidizing agents: peroxides, PbO2 and MnO2....It is accelerated by alkaline environment.

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