The influence of fiber and processing factors on the nature of bonding and fabric performance in thermally bonded nonwoven fabrics

The evaluation of thermally bonded nonwovens was studied to determine the influence of fiber and processing factors on the nature of bonding and fabric performance. Five polyester base fibers varying in linear density and length were chosen, along with a polyester thermoplastic binder fiber. Fiber properties that were measured included linear density, tensile properties, crystallinity measurements and wideangle X-ray scattering. Three levels of concentration (10%, 20%, 30%) of binder fibers were used, along with three levels of bonding temperatures [200°F (93°C), 225°F (107°C), 250°F (121°C)] to b0nd the webs. The physical/mechanical properties of the nonwoven fabrics determined included weight, thickness, flexural rigidity (machine and cross directions), tenacity (machine and cross directions), and elongation (machine and cross directions).

Base fiber linear density was found to be important in fabric behavior, while fiber length had little significance. Films consisting of l00% binder fiber were evaluated to determine the contribution of the binder to a nonwoven system. Increasing bonding temperatures induced greater crystallinity and orientation in the binder fiber, which transferred greater strength to the nonwoven. The fineness and morphological structure of the fibers were found to be an important part in determining fabric properties, such as strength and stiffness.

The effects of processing, specifically temperature and binder concentration, on fabric performance were investigated. The interaction effects of the processing variables were initially evaluated using a iii

iv three-way ANOvA. Further analysis was done by using response surfaces for the key properties of flexural rigidity and tenacity in the machine direction. From this, it was generally found that increasing temperature and concentration produced stronger and stiffer fabrics at a sharp rate.

Several SEM photomicrographs are presented showing binder fiber deformation after the fabric is broken on the Instron Tensile Tester. Fabrics processed at higher temperatures depict binder fibers that show flow characteristics and greater adhesion contrast areas.

The stress-strain curves of all fabrics are presented to aid in the discussion of the individual contributions of the research variables-fiber, binder concentration, and bonding temperature.