Effect of silane-functionalized TiO2 on the optical properties and moisture barrier of silicone resin nanocomposites

This study proposes an effective approach for fabricating silane-functionalized TiO2 nanoparticle/silicone resin (SR) composites that exhibit high transparency, high refractive indexes (RIs), high UV aging resistance, and high moisture barrier. The surfaces of TiO2 nanoparticles (TMOS-m-TiO2) were modified by a sol–gel process using tetramethoxyl (octadecyl) silane (TMOS). The TMOS-m-TiO2 exhibited a significant improvement in compatibility with the SR matrix. The TMOS-m-TiO2/SR composite, containing 0.1 phr of TMOS-m-TiO2, maintained an optical transmittance above 80% in the visible wavelength region. The RI increased with the increase of TMOS-m-TiO2 content, and the RI of the 0.10 phr TMOS-m-TiO2/SR composite was 1.566 (the RI of the neat SR was 1.541). Furthermore, the water vapor transmission rate of 0.10 phr TMOS-m-TiO2/SR composite was 32.8% lower than that of neat SR. This approach can be applied for developing high-performance SR composite materials that can be used in various applications, particularly in light-emitting (LED) diode encapsulants.