Evaluation of surface roughness development of polyamide 6/poly(ethylene terephthalate) blend fibers through fiber diameter measurement using three types of optical equipment

We have reported recently that fibers with surface roughness can be produced through the melt spinning of polyamide 6 (PA6) blended with 20 wt% of poly(ethylene terephthalate) (PET) if the extrusion temperature is lower than the melting temperature of PET. This technology is applicable for the production of fibers for artificial hair. Three kinds of optical equipment, including an optical microscope, were applied for the quantitative evaluation of the surface roughness of PA6/PET blend fibers. There was a good correlation between the roughness values evaluated using the edge-detection type diameter monitor (EDDM) and the back-illumination type diameter monitor (BIDM), even though resolution of the BIDM is lower than that of the EDDM. Through the on-line measurement of spin-line diameter performed at various positions along the spin-line using the BIDM, it was revealed that roughness developed with the increase of distance from the spinneret.