Transport properties of dichloromethane were analysed in high- and low
-density polyethylene films, obtained with different thermal treatment
s, in order to correlate sorption and diffusion with the crystallinity
of the samples. The crystalline fraction of all the analysed samples
was evaluated from density and X-ray data; it ranged from 40%-85%. Fro
m the X-ray diffractograms the reciprocal of the width at half-height
for the strongest reflection was derived for all the samples; it was c
onsidered as an order parameter. It was found that the sorption depend
s only on the fraction of amorphous phase; in fact, the specific sorpt
ion, normalized for the crystallinity of the sample, is constant for a
ll the samples. However, the zero concentration diffusion coefficient,
D-0, varies with the sample crystallinity, but there is no simple cor
relation between these two parameters; rather a transition seems to se
parate two ranges in which the diffusion coefficient decreases with th
e crystallinity. At variance, a linear decrease of the diffusion param
eter with the order parameter, derived from the X-ray diffractograms,
was found in the whole range of crystallinity.