Fatigue behavior of aramid nonwoven fabrics under hot-press conditions - Part IV: Effect of fiber fineness on mechanical properties

We set out to find the most suitable design for heat-resistant nonwoven fabrics to be used as components of laminated cushion materials. The changes in mechanical properties and durability of a nonwoven fabric subjected to repeated hot-press fatiguing treatments depend on the properties of the fiber material and the structure of the nonwoven. In this paper, we focus on fiber fineness, one of the material properties, and discuss its influence on the mechanical properties of nonwoven fabrics after hot-press fatiguing. We find that a nonwoven made of fine fibers has a higher tensile breaking strength and a higher tensile modulus than those made of larger diameter fibers. The nonwovens we prepared have the same fabric basis weight with different fiber diameters. Accordingly, the finer fiber nonwoven has a larger number of component fibers than those of larger diameter fibers, and the degree of fiber entanglement in the finer fiber nonwoven is higher because the number of fibers caught by the needle is greater when the fibers are finer. Tensile breaking strength is proportional to the degree of fiber entanglement, so the finer fiber nonwoven has a higher tensile breaking strength. However, this strength decreases after too many fatiguing treatment cycles, probably due to the deterioration of the fiber material (Nomex). As regards compressive behavior, the finer fiber nonwoven has a lower compressive strain and a higher modulus than those of the larger diameter fibers. These tensile and compressive properties are closely related to the nonwoven's fiber packing factor.