In the silica-filled system, the effect of nano-ZnO
was more pronounced than in the unfilled system
because of the improvement of the dispersion of
nano-ZnO by a dispersing agent for silica in the rubber
matrix. When the content of stearic acid
increased from 0.1 to 0.3 phr in the compound, the
mechanical properties decreased. This was due to
the increase of the lubrication effect caused by the
increased amount of stearic acid.