Derived from aerospace technology, silicone film adhesives are elastomeric materials that use a unique filler to obtain superior mechanical and optical properties. The small particle size of the filler reinforces the silicone polymer matrix and also results in an optically transparent adhesive. These film adhesives offer favorable material properties as well as strong adhesion to many substrates. Both the material and adhesion properties are consistent over a broad range of temperatures and humidity.
Consistent material properties arise partly because silicone film adhesives have glass-transition temperatures that are well below the typical operating-temperature range for automotive applications (-40°C to 150°C). The low glass-transition temperature ensures that silicone film adhesives remain in the rubbery state. In contrast, the bond strength of adhesives with glass-transition temperatures that fall within typical operating-temperature ranges can change drastically as the material changes between the rubbery state and the glassy state.*
In addition, the inherent chemical properties of silicones make them more resistant to moisture and ultraviolet light than many of their organic counterparts. This allows silicone film adhesives to retain their strength and elasticity even after extended exposure to the environment.
For silicones, consistent adhesion to a variety of substrates is achieved by incorporating adhesion promoters in the formulation. Adhesion promoters form covalent bonds between the silicone film and the substrate, resulting in good adhesion properties that are relatively unaffected by moisture, high temperature, or UV light.
This paper compares the material and adhesion properties of silicone film adhesives to the properties of a commonly used organic film adhesive, poly(vinyl butyral).