  In this article, we present a mathematical model that answers a classical
question concerning how much force, which is generally called static friction
force, will it require to initiate the motion of a soft solid block such as
gel, rubber or elastomer on a hard surface for instance glass surface. The
model uses population balance of the bonds between the polymer chains of the
soft solid and the hard surface to estimate rate and aging time dependent
static friction. The model predicts that under certain range of the pulling
velocity, the friction stress at the onset of sliding (static friction stress)
varies as the logarithm of the pulling velocity, as well as the logarithm of
the aging time. These predictions are consistent with the experimental
observations.
