HEAT-TREATMENT OF POLYPROPYLENE FIBERS

Abstract

Crystallinity of polypropylene fibers subjected to wet-heat-treatment under tensionless and stretched states, was examined by large- and small-angle X-ray diffractions.First, the effects of crystallite size and crystal distortion in the broadening of the X-ray diffraction line were studied by applying the Warren's analysis for polypropylene fibers. The X-ray diffraction intensity curves of the (110) and (220) reflections as a set of lattice planes were measured and corrected with the method of Stokes by using Pb (NO3)2 powder as a standard. Applying the Warren's Fourier analysis to the true line profiles thus obtained, the average crystallite size and internal strain along the direction perpendicular to the above reflections were calculated separately.The meridian small-angle scattering intensity curve was also measured.The results are as follows:(1) The degree of crystallinity and the crystallite size increase by heat-treatment, more conspicuous under stretched state.(2) The meridian small-angle scattering intensity and the long spacing increase by heat-treatment, more conspicuous under tensionless state. The sharpness of the scattering peak, however, is more remarkable in the stretched-heat-treatment.(3) These changes in crystallinity become more distinguished in the heat-treatment above 120°C.(4) The distortion in the crystallite decreases by heat-treatment and is the minimum in the heat-treatment at 120°C.From an observation of the relations between the degree of crystallinity and the crystallite size or long spacing, the crystallization in heat-treatment is discussed, as in the previous study.