  We consider FLRW cosmological models with standard Friedmann equations, but
leaving free the equation of state. We assume that the dark energy content of
the universe is encoded in an equation of state $p=f(\rho)$, which is expressed
with most generality in the form of a power expansion. The inclusion of this
expansion in Friedmann equations allows us to construct a perturbative solution
and to relate the coefficients of the equation of state with the formation of
singularities of different types.
