  A transport model based on the mean free path approach to describe pp
collisions is proposed. We assume that hadrons can be treated as bags of
partons similarly to the MIT bag model. When the energy density in the
collision is higher than a critical value, the bags break and partons are
liberated. The partons expand and can make coalescence to form new hadrons. The
results obtained compare very well with available data and some prediction for
higher energies collisions are discussed. Based on the model we suggest that a
QGP could already be formed in the pp collisions at high energies.
