The combination of glass dust and glass fiber as fluxing agents for ceramifiable silicone rubber composites

Abstract

Ceramifiable composites based on silicone rubber (SR) filled with mica powder, glass dust (GD) and short glass fiber (SGF) were successfully prepared for high-temperature applications. The effect of the GD/SGF phr ratio in the fluxing agents on the ceramifiable and mechanical properties of the silicone rubber composites was studied. The results demonstrated that the composites showed excellent properties when the ratio of GD/SGF was 1 : 1 and the corresponding tensile strength was 6.5 MPa. The elongation at break of the composites reached 245.4% and the flexural strength of sintered samples produced at 1000 °C was 16.2 MPa. Thermogravimetric analysis (TGA) results indicated that the char residue was 57.5% at 700 °C, which was much higher than the virgin SR residue. The ceramization process at different sintering temperatures was consequently studied through infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The linear shrinkage and flexural strength of sintered samples increased with increasing sintering temperature from 600 to 1000 °C. The FTIR and XRD tests indicated that the fluorophlogopite mica structure was destroyed and a new cristobalite crystalline phase was formed at elevated temperature. The SEM revealed that a coherent and dense microstructure of sintered samples was formed with increased temperatures, which contributed to the flexural strength improvement.