The differential isoconversional method of Friedman is based on the Arrhenius equation:

f (α): the model function

A: the pre-exponential factor

E: the activation energy

T: the temperature

t: the time

Friedman has applied the logarithm of the conversion rate d α /dt as a function of the reciprocal temperature at any conversion α:

As f(α) is a constant in the last term at any fixed α, the logarithm of the conversion rate d α /dt over 1/T shows a straight-line dependence with the slope of m = -E/R.

By the extension of the expression

with

one can predict the reaction rate or reaction progress having determined  and using the following expression: