Numerical Simulation and Experimental Study of the Polypropylene Polymer Air Drawing Model and Air Jet Flow Field Model in the Spunbonding Nonwoven Process

Abstract

The air drawing model of the polypropylene polymer and the model of the air jet flow field in a spunbonding process are presented and solved by introducing the numerical computation results of the air jet flow field of an aerodynamic device. The air jet flow field model is simulated by means of the finite difference method. The effect of the density and specific heat capacity of polymer melt at a constant pressure changing with the polymer temperature on the fiber diameter was studied. We find that the variation of the density and the specific heat capacity of polymer melt at constant pressure with polymer temperature greatly effects the fiber diameter. Compared with the existing drawing model, the new ones include more processing parameters and are more accurate. The newly developed formulas were incorporated into a spunbonding theoretical model to predict the fiber diameter of nonwoven web. The numerical simulation computation results of the distributions of the z-components of the air velocity match quite well with the experimental data. The air drawing model of polymer is solved with the help of the distributions of the air velocity measured by particle image velocimetry (PIV). The model’s predictions of the filament fiber diameters, crystallinities, and birefringences coincide well with the experimental data. It can be concluded that the higher initial air temperature can yield finer filament fiber diameter and the higher initial air velocity can produce finer fiber diameter as well. The experimental results show that the agreement between the results and experimental data is much better, which verifies the reliability of these models. At the same time, also, they reveal great prospects for this work in the field of computer assisted design (CAD) of the spunbonding process.