Sorption and diffusion of dichloromethane vapour were measured in poly(aryl ether ether ketone) films after different ageing times. In the fresh samples the diffusional behaviour is characterized by two stages: in the first stage the diffusion coefficient D is weakly dependent on concentration, and transport mainly occurs through a frozen system; whereas in the second stage a steep dependence of D on concentration was found. The aged samples also show an intermediate stage, characterized by an anomalous or non-Fickian sorption behaviour. Furthermore the diffusion coefficients of the aged samples are lower than those of the fresh samples, in agreement with a reduced fractional free volume. Ageing at a temperature slightly lower than the glass transition temperature decreases the sorption at low activity, leading to the suggestion that ordered domains, impermeable to the vapour at low activity, are formed at this temperature. The process of solvent-induced crystallization on the amorphous samples was investigated, and it was found that crystallization is induced after activity 0.7. Both the fresh and the aged samples show the same behaviour, although the level of crystallinity attained was found to be higher for the latter samples.
Посилання на статтю:
Transport properties of dichloromethane in glassy polymers: 5. Poly(aryl ether ether ketone) / A. Michele and V. Vittoria // Polymer. – 1993. – Vol 34. – P. 1898-1903.