responsible for the high strength of gum NR vulcanizates.
Fig. 4 displays the tear strength of various NR vulcanizates. The gum exhibits the lowest tear strength while the
vulcanizates having equal amounts of fillers give similar
tear strength. Although, it is established that spherical
particles can blunt the crack tip more effectively than the
plate-shaped filler having high aspect ratio particles [14],
such a small amount of CB and silica (6 phr) used in this
experiment may not be sufficient to effectively blunt the
tear tip. However, the tear strength of CB- and silica-filled
NR vulcanizates markedly increases when they were
prepared to have similar hardness to that of clay-filled