Preparation of Cellular Silicone Elastomers Using Epoxide-Functionalized Silicones

While silicone foams have existed for decades, stringent application and regulatory requirements in various fields have driven the need to develop innovative silicone-based foaming solutions. Incumbent silicone foams mostly utilize precious metal-based catalysts (e.g., Pt-based Karstedt's catalyst), which makes them expensive foam materials and introduces process safety-related concerns due to evolution of flammable hydrogen gas as a byproduct. In this exploration study, tris(pentafluorophenyl)-borane (B(C6F5)(3)) was studied as a commercially available alternative to the Pt-catalyst and used with an epoxide-functionalized silicone. Rheology study shows that the cure performance could be manipulated by varying inhibitors, B(C6F5)(3) loadings, molecular weights of functional silicones, and concentrations of functional groups. Closed-cell silicone foams (density similar to 0.7-0.9 g/cm(3)) were prepared using epoxide-functionalized silicones for the first time with air or fluorohydrocarbon as the frothing or physical blowing agent. Elimination of flammable gaseous byproducts like hydrogen improves safety of foam preparation in a poorly-/nonventilated environment. Also, the ability to use B(C6F5)(3) for silicone foam preparation creates opportunities when the use of traditional Pt-catalysts is problematic.