Networked Silica with Exceptional Reinforcing Performance for SBR Compounds: Interconnected by Methylene Diphenyl Diisocyanate

A networked silica (NS) prepared by interconnecting silica particles with polymeric methylene diphenyl diisocyanate (MDI) was developed for use as a highly effective reinforcing material for rubber compounds without the need to add silane coupling agents. MDI incorporated onto the silica surface formed networks among neighboring silica particles with urethane linkages and produced NS at low cost. The TEM photographs illustrated the improved dispersion and formation of openings among the silica particles, which could allow easy intrusion of rubber molecules. The NS showed a high reinforcing performance for styrene—butadiene rubber (SBR) compounds, suggesting the possibility of replacing the silica reinforcing systems with coupling agents. Due to the absence of any silane-containing coupling agents, the NS does not suffer the disadvantages associated with coupling agents. Since the NS reinforces rubber compounds by the physical entanglement between rubber molecules and the MDI chains, high loading of the NS is more effective in enhancing the mechanical properties of rubber compounds.