Optical and thermal properties of PI/TiO2@SiO2

The optical and thermal properties of polyimide (PI) composite films are very important parameters in the application of electrical insulation materials. The reports show that the ultraviolet (UV) and heat from aging conditions always destroy the PI. In this background, a novel method using SiO₂-coated TiO₂ (TiO₂@SiO₂) as dopant has been proposed and the composite films with 15% content of SiO₂@TiO₂ are prepared. Surface morphology and element distribution, phase structure, optical and thermal properties of the films are tested and characterized by scanning electron microscope (SEM), X-ray diffraction instrument (XRD), UV-Vis spectrophotometer (UV-Vis) and thermal gravity analysis (TGA),respectively. The results show that inorganic nano-particles are well dispersed into PI, the content of SiO₂ in TiO₂@SiO₂ is about 12%, TiO₂@SiO₂ in PI/TiO₂@SiO₂ is about 15%. The light-radiation resistant properties of PI/TiO₂@SiO₂ is similar to pure PI, and are much better than PI/TiO₂. TiO₂@SiO₂ absorbs most of the UV in PI/TiO₂@SiO₂, and SiO₂ layer with broad band gap prevent released electron and hole from effecting the stability of PI. The decomposition temperature of the films will not be affected by nano-particles, but the weightlessness rate (residual quality fraction) of the films are affected obviously under the same heat-radiation conditions, the sequence of excellent thermal performance is PI/TiO₂@SiO₂>PI/TiO₂>PI. The structure, optical property and thermal property of the materials are closely related to each other. To some extent, the structure of TiO₂@SiO₂ improves the optical performance and thermal performance of PI.