| Abstract: | Drawing of quenched polyethylene at 60°C transforms the spherulitic sample into a material with fibrous structure. As a consequence, the sorption and still more the diffusion of C2Cl4 vapours are drastically reduced. Annealing at 120 and 125°C increases the crystallinity and hence reduces the amount of the amorphous component. In spite of that, it enormously increases the transport properties. It restores the sorption per unit volume of amorphous component to a value which, corresponding to completely relaxed amorphous component, is even higher than that of the starting undrawn but quenched material. The diffusion constant after annealing is a little smaller than in the undeformed original sample and shows the same small dependence on concentration in striking contrast with the drawn material. One concludes that the restoration by annealing of the sorption and diffusion coefficients for drawn polyethylene to the values of the undrawn material is a consequence of the complete relaxation of polyethylene chains, in particular of tie molecules, in the amorphous component which completely overcompensates the effects of a reduced amorphous fraction and the increase in crystal perfection. |
