Permeation, solution, and diffusion of water in some high polymers

Abstract

The equilibrium sorption isotherms of water in polyethylene terephthalate, ethyl cellulose, and rubber hydrochloride have been measured at 25°C. by means of the quartz helix technique. The permeability constants and the diffusion constants have been measured on the same polymers and on polyethylene and polypropylene by the time‐lag technique of Barrer but with a modified apparatus. The solubility coefficients from the sorption measurements (values for polyethylene and polypropylene have been previously reported) are compared with those obtained as the quotient of the permeability and diffusion constants. In the case of polyethylene, polypropylene, and polyethylene terephthalate, excellent agreement between the two sets of values were obtained, but with rubber hydrochloride and ethyl cellulose the sorption values are much higher. These differences are interpreted in terms of clustering of water vapor in the film at higher relative humidities. The modified time‐lag technique showed concentration‐independent diffusion constant for all five polymers.

Water permeability of plant cuticles: permeance, diffusion and partition coefficients

“…D tends to increase as K increases. This type of dependence has also generally been observed with most synthetic polymer membranes (Yasuda and Stannett 1962).…”

“…With p and D known, the partition coefficient (K) can be calculated (Crank 1975;Rust and Herrero 1969;Yasuda and Stannett 1962):…”

The Structure of Water Sorbed to Polymethoxyethylacrylate Film as Examined by FT–IR Spectroscopy

“…For example, the D values of water vapor in polyethylene and poly-(vinyl alcohol) films were reported to be 2.0 × 10 −7 cm 2 · s −1 (33) and 2.24 × 10 −12 cm 2 · s −1 (34), respectively. In many previous studies, the diffusion coefficients of water vapor in polymeric materials were determined by a gravimetric method (32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42), and only a few studies have been made using spectroscopic techniques because of insufficient sensitivity FIG. 6.…”

Concentration dependence of the time lag for diffusion

“…For several vapor-polymer systems differences have been observed and are usually attributed to physical effects resulting in a timedependent contribution to the diffusion coefficient which vanishes in the steady state. [6][7][8] It is the purpose of this communication to stress that when D varies with C, the relative variation of L with C over a finite concentration range is always considerably smaller than that of D with C. This is suggested by the form of eq. (Fig.…”