Study on Structure and Properties of Polypropylene/Polyamide 6 Blend Fiber (Part II). Dye-Affinity of Polypropylene/Polyamide 6 Blend Fiber and Crystallization Behavior.

Abstract

The relationship between mixing state and dye-affinity of polypropylene/polyamide 6 (hereafter “PP/PA6”) blend fiber was investigated by examining the crystallization behavior. The peak corresponding to the crystallization of PA6 in the DSC curve obtained by cooling the melted blend fiber depended upon the content of PA6, the melt viscosity ratio of both components (η PP/η PA6), and the existence of the compatibilizing agent. Any crystalline peak was hardly observed in a DSC curve of a sample containing PA6 of 40% or less and showing the melt viscosity ratio of 0.4 or less. The heat of crystallization of PA6 correlated with the content of PA6 in the surface layer of fiber determined from the infrared absorbance spectrum. The behavior of the heat of crystallization depended upon the dispersion state of both components. It was considered, therefore, that the peak corresponding to the crystallization of PA6 was low for the blend fiber composed of better dispersed components, because the crystallization of PA6 was hindered by the melted PP. The dye molecules were hardly diffused and PA6 was hardly bled to the surface layer in these fibers. In the blend fiber composed of the phase-separated components, however, it was considered that the dye molecules were relatively easily diffused and the content of PA6 in the surface layer of fiber was relatively high in the samples in which the crystallization of PA6 was hardly hindered. No peak due to PA6 crystallites was observed in the wide-angle X-ray diffraction pattern of a sample exhibiting no crystallization peak of PA6.Thus, the dye-affinity of the fiber depended upon the dispersion state of both components, and could be improved by controlling the dispersion of both components.