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Microstructural analysis of melt-blown nonwoven fabric by X-ray micro computed tomography

The structures of melt-blown nonwoven fabric, including the fiber volume fraction and fiber orientation, are decided by the melt-blowing conditions, such as the die-to-collector distance (DCD), air suction and air flow rate. In this study, the effects of these melt-blowing conditions on the structure of melt-blown fabric was investigated by X-ray micro computed tomography with a resolution of 1 µm/voxel and a measurement area of 1 mm2. The structural profile along the thickness direction of the fabric was also analyzed. Obtained averages of fiber diameter and basis weight were almost identical to the results of scanning electron microscopy measurements and tests following the standard of International Organization for Standardization. Samples produced with insufficient air suction showed larger deviation of basis weight on the 1 mm2 scale compared with those produced with sufficient air suction. The fiber volume fraction changed steeply around the fabric surface, which was attributed to surface roughness. Insufficient DCD increased the fiber diameter and surface roughness, and decreased the thickness of the fabric. The fiber volume fraction gradually decreased from the collector side to the die side for fabrics with sufficient DCD. The fibers were oriented along the machine direction rather than the cross-machine direction for all layers and samples, and orientation profiles corresponded to the zero-span tensile strength of corresponding samples.