and is reflected in the values of Vr. Moreover,
the results of Q, Mc, and cross-link density confirmed the formation
of crosslink network structure. However, increasing crosslinks over
an optimum level cause localized stresses, which results in lower
values of TS which we can explained as follow. Tensile strength,
unlike the tensile stress at a given elongation and hardness, does
not rise continuously with the number of crosslinks. Instead it rises
with the number of crosslinks until an optimum is reached, after
which if crosslinking is continued (in which case over-crosslinking
takes place), it initially falls steeply.