Improvement of dispersion stability of filler based on fly ash by adding sodium hexametaphosphate in gas-sealing coating

Abstract Gas emission is a major security risk in coal mining. Seal coating is an effective method for preventing gas from escaping, but the stability of inorganic particles in the coating has great influence on the sealing performance. This research was designed to study the effect of SHMP on the stability of a gas-sealing coating filler based on UFA. The effect of SHMP on powder dispersion behaviors was systematically investigated using a zeta potential tester, particle size analyzer, FT-IR, and SEM- EDS. To explore the dispersion mechanism of SHMP on typical powder materials (such as fly ash, carbon black, and graphite), the interaction energy among particles was calculated according to the classical and extended DLVO theory. The results indicate that the surface hydrophobic effects of graphite and carbon black were the main contributing factors to agglomeration. Further, the dispersant SHMP increases the interparticle electrostatic repulsions and steric hindrance, preventing particle agglomeration and ensuring the stability of fly ash-based filler in gas-sealing coatings. The results of pilot spraying test in a coal mine show that the added dispersant improved the gas-sealing efficiency of the coating and helped in its application in a coal mine.