Experimental and numerical analysis of fiber characteristics effects on fiber dispersion for wet-laid nonwoven

Dispersion and separation of fiber bundles into individual fibers, requires exposing them to a shear stress field to overcome inter-fiber frictional forces. To this end, fiber-mixing tanks are usually used to enhance shear and agitation in water and help the dispersion process. The required time and necessary agitation to separate and disperse fibers depend on fibers' characteristics. It is well known that excessive agitation will give rise to the formation of rope defects in the output because of the high-energy vortices and optimizing the break up time is important in wet-lay process. In this work, experimental and numerical studies were done to investigate the effects of fiber characteristics on their dispersion in water for wet-laid nonwoven. The effective forces were analyzed using a one-way modeling of fiber behaviors in a stirred mixing tank. Results show that when the fiber diameter is increased, the required time for breaking up of fiber bundles and clumps is increased. The effects of fiber types on fibers break up and dispersing time, were also investigated. In the experimental work, an on-line vision system was designed to observe the dispersion behavior of polyester fibers. The effects of fiber length and fineness on the created defects (i.e. logs and ropes) in dispersion process, as well as on the dispersion speed, were studied. The results confirm that defects are increased by rising fiber length and fineness. It is also shown that increasing fiber length and fineness, decreases the required time for fiber clumps to be opened and reach a maximum number of individual fibers. On the other hand, when fiber length and fineness is increased, the dispersion speed increases.