The significance of the zero-concentration diffusivity value obtained from integral desorption data

n-Hexane zero-concentration diffusivity in high density polyethylene obtained ‘indirectly’ from integral desorption measurements using the free volume concept was compared with the zero-concentration diffusivity obtained directly at low-n-hexane activities using a quartz-spring system. The difference between the results obtained by the indirect and direct methods was within the experimental error. The concentration dependence of the diffusivity predicted by the Cohen–Turnbull–Fujita free volume theory was in accordance with experimental data.