Dynamic Analysis Model for the Diffusion Coefficient in High-Viscosity Polymer Solution

Abstract

An accurate mass transfer model is required to calculate the diffusion coefficient in polymers to describe the mass transfer of volatiles in process intensification, especially in the devolatilization units. However, the diffusion coefficient actually is variate rather than a fixed value due to the changing concentration and viscosity of polymer in the process of devolatilization. In this work, removal rates of the volatiles in liquid film were obtained by the intelligent gravity analysis, and a discrete mathematical model was established to compute the instantaneous dynamic diffusion coefficients. On the basis of a large number of experimental data, a correlation of diffusion coefficients was developed by dimensionless regression analysis with temperature, concentration, viscosity, molar mass, molecular polarity, etc. It can well describe the diffusion process in polymers. Furthermore, a molecular simulation was conducted to explore the proper means of the bonding method and force field in the calculation of the diffusion coefficient.

Improving Powder Performances of d-Ribose through Spherulitic Growth

“…Since the growth of crystals in highly viscous systems is mainly controlled by diffusion, 22,23 we believe that system viscosity (V) and solution supersaturation are the main factors affecting the morphology of D-RIB spherical crystal aggregates, as shown in Figure 2b,e,h,k,n. First, we prepared the saturated solution of D-RIB in each alcoholic solvent at 333.15 K; then, we determined the viscosity of the solution system [not crystallized at this time; the viscosity of the supersaturated solution was measured by a rotational viscometer (NDJ-9S, Shanghai Lichen Bangxi Instrument Technology Co., Ltd., China)] when the saturated solution (333.15 K) was cooled down to 293.15 K. Methanol has the lowest viscosity of the single-alcohol solvents.…”

Coarsening of dendrites in solution-based freeze-cast ceramic systems

“…Changing the coarsening temperature may alter the diffusion coefficient. However, if the diffusion coefficient ( ) follows an Arrhenius behavior [68], or a reptation model in the case of long-chained polymers, the temperature dependence of is sufficiently small (less than 1 % increase) that it cannot account for the 70 % and 40 % increase in coarsening rate for primary and secondary pores, respectively, that occurs with coarsening at 4 °C compared to 2 °C. Instead, the enhanced coarsening rate with temperature is likely due to the increase in liquid volume fraction.…”

Mechanism of NO removal in selective catalytic reduction based on γ‐Fe2O3 catalyst doped with Mg element

“…The basic principle of the SCR method is to selectively react with some reductive gas and NO x in a suitable temperature range and generate non-toxic N 2 and H 2 O under the catalytic action of the catalyst. [4] The catalyst plays an important role in the NH 3 -SCR process and is the core of the reaction process. At present, vanadium-based catalysts are widely used in the field of industrial de-NO x , because they have excellent lowtemperature activity and SO 2 poisoning resistance and are one of the industrial catalysts widely studied by many scholars.…”