Sorption and transport studies of water in Kapton polymide. I

Abstract

SynopsisSorption isotherms and diffusion coefficients of water in a 0.3-mil Kapton polyimide film at 30,45, and W C are reported. The data are well described by the dual mode sorption and transport models at low activities. At high penetrant activities, clustering of water is suggested by a Zimm-Lundberg analysis of the sorption data and the fact that the diffusion coefficient for water decreases with increasing external vapor activity. The effect of temperature on the diffusion coefficients at infinite dilution and the dual mode sorption parameters kD, b, and Ch are presented and discussed. The magnitude of the activation energy of the diffusion coefficient at infinite dilution, 5.4 kcal/mol, is smaller than the corresponding activation energy in more flexible chain polymers, perhaps suggesting that rather small backbone motions are associated with diffusion of water through the Kapton matrix. The predictions for the isosteric enthalpy of sorption from the dual mode model are presented and compared with the values determined from graphical analysis of the sorption isotherms performed independently without reference to the dual mode sorption model.

The states of water in glutinous rice flour characterized by interpreting desorption isotherm

“…Figure 4 shows that water molecules preferred to cluster at higher temperature. Similar trend was observed by Yang et al (1985) for Kapton polymide in glass state, and Rawat and Khali (1998) for wood equilibrated at a w levels of up to 0.98. According to the park model, water molecules prefer to cluster at lower temperature (Table 1), which was contradictory to the prediction from the Zimm-Lundberg method (Eq.…”

Experimental Studies and Modelling of Sorption and Diffusion of Water and Alcohols in Cellulose Acetate

“…This is due to the fact that the classic BET equation (with two parameters) is not complex enough to account for the whole sigmoidal isotherm ; it is considered to give good agreement with experimental values for water activities below 0É5. 28,29 The GAB model, which showed efficiency in the case of water sorption in foods and related natural polymers,30,31 seems to be suitable for such a sigmoidal isotherm with a clear upward curvature at high activities :…”

“…7) is reminiscent of water sorption in cellulose,26 and in glassy polymers such as nylons27 and polyimides. 28 The part of the isotherm at low activities corresponds most-probably to the sorption of the vapour on speciÐc sites in the polymer materials. At higher activities (i.e.…”

Water-transport properties in polyetherimide blends with a liquid crystal polymer

“…A concentration dependence of the Henry's coefficient has been proposed in some cases, [23][24][25] whereas Berens 26 introduced the FloryHuggins theory, as a generalized version of the Henry's term, in order to fit sorption data in the vinyl choride/PVC system. Similar, satisfactory, results using a Flory-Huggins contribution were reported by Hernandez et al 19 in fitting the experimental data of water sorption to an amorphous polyamide.…”