The diffusion of gases in semicrystalline polyethylene and its melt

Abstract

ABSTRACT:The fractal analysis and the cluster model of the polymer amorphous structure make it possible to account for a change in the diffusion coefficient in polyethylene both above and below the melting temperature. The proposed interpretation explains the diffusivity jump at the melting point as resulting from the disintegration of localorder regions. The formation of these regions is due to polyethylene crystallization.

Fractal model of the free volume of vitreous poly(vinyltrimethylsilane) from data on gas diffusion

“…However, among all the microholes, only the microholes that satisfy the criterion d p > d mol are accessible for diffusion. This condition is taken into account in traditional gas transfer models [2] and fractal (more precisely, multifractal) models [16]. The accessible fractal free volume can be defined as follows:…”

Modelling of single bubble growth in carbon nanofibre filled mesophase pitch during carbonization

“…where k xo is the reaction constant, Q x is the reaction activation energy, R g is the gas constant, T is the absolute temperature, D 0 is the diffusion constant and Q D is the diffusion activation energy. The parameters for the diffusion coefficient were based on the literature data for diffusion of gases in polymer and coal melt systems [17,23,24]. A single D 0 value of 1.0 × 10 −3 cm 2 s −1 was used and the activation energy was varied from 17.3 to 57 kJ mol −1 .…”

“…Knowledge of the diffusion coefficient is needed to produce simulated growth rates that are consistent with the physical system. The activation energy values used were estimated using experimental and numerical values for diffusion coefficients in polymer melts [17,23,24], as no direct data are available for the diffusion coefficient of methane or other small hydrocarbons in a mesophase pitch melt. The diffusivity and activation energies are consistent with those reported for coal melts [29].…”

The Solubility of Hydrocarbon Gases in Glassy Polymers: Fractal Modeling

“…In this sense, the fractal modeling is an important tool for this purpose. Recently, authors proposed the fractal analysis of the gas permeability in semicrystalline polyethylene [7,8].…”