Achieving Functional Excellence with Silicone Coatings

NOVEMBER 2004 37 W hen applying silicone coatings, it is essential to view the final product, not as a series of separate product processing steps and components, but as an integrated system. The functional performance of the silicone coating is affected not only by the physical properties of the silicone, but also by the application process and the performance characteristics required by the final product. The impact on the success of the final application could be significant if the effect of the process, in combination with the properties of the silicone coating, is not considered. Physical property influences associated with various substrates (eg. nylon, polyethylene, polyester or glass-fibre) must also be studied. Equally important is fibre denier and fabric tightness or density, which is a function of sett for woven fabric and basis weight for nonwovens. Careful consideration must be given as to how the physical properties of the silicone will interact with the substrate’s surface to determine whether the performance observed in the final product is a result of film formation versus coating penetration. This article discusses how optimization of the coating process can help balance component properties, end-product attributes (such as barrier protection) and economic considerations. It also introduces a new silicone technology that enables the user to “dial in” the right balance of properties for the silicone application. Physical Property Considerations for Silicone Coatings The physical properties and resulting performance attributes of silicone fabric coatings vary, usually within a certain range. Different property combinations can be achieved through crosslinker and filler changes. This will, however, require tradeoffs in either physical properties and/or economics. For example, while it is possible to formulate a coating that delivers high tear strength, high tensile strength and high elongation, this usually comes at the expense of lower durometer, higher viscosity and greater raw-material cost.