On the importance of fiber curvature to the elastic moduli of electrospun nonwoven fiber meshes

Abstract

Adequate mechanical integrity of nonwoven fabrics is generally a prerequisite for their practical usage. Nonwoven fiber mats of poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) with average fiber diameters from 0.1 to 3.6 microns were electrospun from solutions in dimethylformamide and formic acid and their in-plane mechanical response characterized. Two quantitative microstructure-based models that relate the Young's moduli of these fabrics to those of the fibers are considered, one assuming straight fibers and the other allowing for curved fibers. It is found that the model allowing for curved fibers provides a quantitative relationship between the Young's moduli of the mats and those of the fibers themselves. The governing factors that affect the mechanical properties of nonwoven mats are the porosity of the mats, the intrinsic fiber modulus, and the average fiber diameter, curvature (or "curl") and distance between fiber-to-fiber junctions. Especially for submicron diameter fibers, both the intrinsic fiber properties and fiber curvature make important contributions to the mechanical behavior of their nonwoven fabrics.2

Materials and Processes for Ion Permeable Separating Membranes by Electro-Spinning

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Mechanical behavior of bilayered small-diameter nanofibrous structures as biomimetic vascular grafts

“…The influence of the scaffolds and its material parameters (fiber diameter, curvature and orientation; material flexibility and rigidity, etc.) and how they affect the mechanical response, was investigated before (Rizvi et al, 2012;Pai et al, 2011). As in random nanofibrous materials, not all the fibers are in the load-bearing direction, the response would depend on how many fibers are recruited and aligned during the tensile test.…”

Structural, mechanical, and tribological properties of electrospun poly(hexamethylene adipamide) fiber mats

“…For some applications such as tissue engineering, where a soft, porous matrix is desirable, this may be an advantage; however, for many applications of nonwoven mats, notably membranes and textiles, for example, modest improvements to the mechanical integrity without significant losses in the inherently high porosity or specific surface area would be highly desirable. Although many experimental studies have been conducted on the mechanical properties of conventional nonwoven fabrics, there are a limited number of reports that account adequately for the observed mechanical properties of mats comprising electrospun fibers [14,15]. In recent years several research groups have demonstrated significant improvements to the Young's modulus and yield stress of electrospun polymeric fiber mats by various forms of post-spinning techniques such as thermal annealing [16,17], mechanical drawing [18], hot pressing [19], and solvent vapor treatment [20].…”