Modelling of the Through-air Bonding Process

A computational fluid dynamics (CFD) modelling of the through-air bonding process of nonwoven fabric production is reported in this article. In the through-air process, hot air is passed through the fibrous web to heat and melt polymer fibers. Molten polymer subsequently flows to the point of contact between any two fibers to produce a bond. Two different modelling strategies are adapted to produce a comprehensive understanding of the through-air bonding process. In macroscale modelling, a CFD model is developed treating the whole web as a porous media in order to investigate the effect of process parameters. Results reveal that the time required to heat and melt the fibers decreases with the increasing porosity of the web and the velocity of hot air. The CFD modelling technique is then used to analyze the bonding process at a more fundamental level by considering the bonding of individual fibers at microscale. The effects of the fiber diameter, bonding temperature and contact angle between two fibers on the bonding time are investigated. Results show that the time required to bond fibers is weakly related to bonding temperature and fiber diameter. Fiber orientation angle, on the other hand, has significant effect on the progression of bond formation.