On the basis of Fich's diffusion law

a method of calculation of gas diffusion coefficient in polymer from the value of inflection point on differential diffusion curve is derived

by which the attainment of steady state is not necessary

thus experimental time can be greatly reduced. This method was tested on nylon 1010 and nylon 1010/polyethylene/poly (ethylene-g-maleic anhydride) blends. The results calculated are in uniform with that from time-lag and t1/3 methods

and accord with experimental values.