Fabrication of Silicone Rubber Foam With Low Dielectric and Excellent Cushioning via Surface Fluorinated Hollow Microspheres

ABSTRACT This study presents a novel strategy for fabricating multifunctional silicone rubber foam with low dielectric constant and excellent cushioning properties by incorporating surface fluorinated hollow microspheres. Thermally expandable microspheres (TEMs) were firstly modified with 3,3,3‐(trifluoropropyl) trimethoxysilane (TFPS) by the bridge of γ‐aminopropyl triethoxysilane (KH550). The effects of pH and TFPS dosage on fluorine content on the surface of the obtained fluorinated and silane‐modified TEMs (F‐TEMs) were investigated. When F‐TEMs were added into room‐temperature‐vulcanized silicone rubber (RTV) and served as both foaming agents and dielectric modifiers, the obtained fluorinated silicone rubber foam (FSR foam) showed a uniform closed‐cell structure with enhanced interfacial compatibility. Based on the optimized fluorine content and addition of F‐TEMs, the low dielectric constant of 2.51 and the dielectric loss of 0.066 at 10 Hz, excellent cushion property, low density, and good thermal stability of the composite foam were achieved simultaneously. This work provides a scalable and efficient approach to developing multifunctional polymer foams suitable for high‐frequency electronics, aerospace, and wearable devices.