Fractal dimension of polymer sorbents

Some methods of defining certain features that characterize polymolecular sorption of water vapor by polymers are discussed: the fractal dimension, through the Frenkel-Halsey-Hill formalism; BET; the sorption film area, through the Kiselev equation and the differential function of pore surface distribution. In the framework of the BET theory, a new approach is proposed to define the surface fractal dimension of polymer sorbents, which is based on finding the number of the polylayers. The proposed method is compared with the existing ones. The proposed definition of the surface fractal dimension allowed to derive a three-parameter sorption isotherm equation, which takes into consideration the sorbent fractal properties in the domain of the relative change of water vapor pressure, is 0.05 less than or equal to x less than or equal to 0.95.