Effect of coal gasification fine slag's particle size on the processing properties of styrene butadiene rubber and natural rubber composites for replacing commercial silica

As a by-product of coal chemical industry, highly-discharged coal gasification fine slag has caused environmental problems such as land occupation and dust pollution. In this work, a high-ash coal gasification fine slag (AFS) and its ball milling products were selected to replace commercial precipitated silica (P-silica) and Micro-silica (M-silica) to fill Styrene-butadiene rubber (SBR) and Natural rubber (NR), respectively. The results showed that the filler network type of SBR changed from Particle Direct Contact Network (PDCN) to Rubber Shell Contact Network (RSCN) due to the replacement of P-silica by AFS fillers and the vulcanization speed improved. However, the replacement of M-silica by AFS-filler didn't change the filler network type of NR composites and resulted in a decrease of vulcanization speed. In both SBR and NR composites, the vulcanization speed, tensile strength, and activation energy of rubber molecular chain movement increased with the decrease of AFS-filler's particle size, which indicates that the reduction of AFS-filler's particle size is beneficial to the improvement of vulcanization speed and reinforcement. In addition, the T 90 of SBR filled with AFS fillers at 5 phr substitution was reduced by 29.0 %–43.3 % and the tensile strength was increased by 4.6 %–44.6 % compared to pure P-silica filled SBR. More importantly, the substitution of commercial silica by AFS reduces energy consumption in the rubber industry and opens up new ideas for improving the universality of coal gasification fine slag as rubber fillers.