Short-fiber-reinforced structural silicone for facades: Potential & performance

Silicones are elastic sealants and adhesives. They are able to compensate for unevenness and temperature longitudinal expansions between various joining materials. In accordance with the requirements of ETAG 002-1, these adhesives combine the optimal weather and UV resistance with very good adhesion. As a result, they are the only adhesives suitable for structural sealant glazing in bonded façades. Analogous to the effect of fiber-reinforced plastics, where a load is transferred from the polymer matrix to the fibers, the specific use of yarns, cords and fabrics in elastomers already enables high-performance composite materials for conveyor belts, tires and tubes. It is hypothesized that this effect can be transferred by using short fibers to create fiber reinforced structural silicone adhesives (FRSSG). This article investigates the possibilities and technical risks associated with mixing short fibers into 2K silicone adhesives for use in the building industry. This study covers 8 different short fibers or fillers, each in 3 different proportions. In a first step, we conducted 125 dogbone tensile tests (DIN EN ISO 527) to describe strength, stiffness and failure behavior of FRSSG in an exploratory fashion. A wide range of natural or industrial fibers have different effects on the mechanical properties of a silicone adhesive. For instance, cotton fibers have been shown to enhance adhesive stiffness by a factor between 50% and 500%. In a second step, adhesion tensile tests (ETAG 002-1) using 50 specimens were performed to compare typical technical properties. An increase in strength by 5% to 30% was recorded. In total, 175 specimens were tested for the effect of fibers on technical properties. The results will open up interesting applications and great research potential.