Preparation of transparent hard GPTMS-Al₂O₃ thin films on a polycarbonate substrate

Using polycarbonate (PC) due to its incredible properties as a suitable replacement for inorganic glasses has been increasing. Nevertheless, the low hardness limits its applications in more industries. Hence, it requires to be coated with hard anti-scratch optical coatings to overcome these limitations. In the current work, sol-gel-prepared thin films based on (3-Glycidyloxypropyl) trimethoxysilane (GPTMS)-Al₂O₃ were applied on PC substrates. First, silica and alumina sols were synthesized by a sol-gel process, individually. Then, the prepared sols were mixed at different ratios and dip-coated on the plasma etched pretreatment PC substrates. Curing of the samples was done in an oven at 100 °C. The produced thin films were characterized by field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Attenuated total reflectance -Fourier transform infrared spectroscopy (ATR-FTIR), and UV/Vis spectroscopy techniques. The obtained results indicated that the PC hardness increased from 6B to H by deposition of nano-hybrid coatings. After applying a nano-hybrid coating, transmittance was increased from 88 % to 91 % and the reflectance decreased from 10 % to 5 %. Sample with a 1:4 GPTMS-Al₂O₃ ratio showed the best results.