Silyl-terminated polyurethanes (SPUR) are the basis for numerous adhesives and sealants used worldwide. The high performance of this hybrid technology is a result of the synergy between the silane-curing mechanism and polyurethane backbone.1 SPUR polymers generally cure at room temperature and offer good durability.
One of the major requirement of sealants is to have a certain thixotropic behavior, resulting in sag-specific properties for successful practical application. The thixotropic agent predominantly used in adhesives and sealants is fumed silica. In addition to thixotropy, fumed silica provides reinforcement and mechanical properties. Although fumed silica contributes to the required structure-imparting properties, it does bring a number of limitations. One of the major disadvantages is the very fine dust nature of the material, which makes it unpleasant and difficult to handle. Another drawback is the requirement for high-shear, capital-intensive dispersion equipment for adequate incorporation.