Synthesis and Physical Properties of TiO2-Epoxy Resin Nanocomposite with High Refractive Index and High Transparency

Along with the evolution of technology, the fabrication of the organic-inorganic nano composite was developed by blending the nano-sized particles and the polymers. anocomposites had many advantages such as high refractive index, low thermal expansion coefficient, good thermal stability, and excellent mechanical properties. The high refractive index materials can be widely used as encapsulants , optical waveguides and optical lenses, etc. In this research, crystalline TiO2 nanoparticles with an average size smaller than 30nm were successfully synthesized via sol-gel process. After surface modification, the TiO2 nanoparticles were stabilized and well dispersed in organic solvents to form transparent TiO2 nanoparticle colloidal solutions. Through the UV-vis spectra, we studied how the surfactants influenced the optical properties of surface modified TiO2 in solution state. Then, the surface modified TiO2 nanoparticle solutions were mixed with epoxy resin to fabricate organic-inorganic hybrid materials with high refractive index and high transparency. Differential scanning calorimetry(DSC) was used to investigate the cure kinetics of the composite. We found that the activation energy (Ea) determined in accordance to Kissinger’s method, the peak temperature of exotherm (Tp), and the heat of curing(∆H) decreased with increasing concentration of surface modified TiO2. The refractive index of cured nanocomposite films was in the range of 1.54–1.73 at 633nm, which linearly increased with the content of TiO2 nanoparticles from 0 to 40 wt %. The transmittance of the cured nanocomposite was higher than 90% because the well dispersion of surface modied TiO2 in the polymer matrix, which avoid the effect of light scattering caused by particle aggregation. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), thermogravimetric analysis (TGA) and microhardness tests were applied to characterize the cured nanocomposite materials.