Thermal characteristics and crystallinity of Ziegler–Natta isotactic polypropylene/metallocene isotactic polypropylene polyblended fibers

Abstract

Ziegler-Natta isotactic polypropylene (ZNiPP) and metallocene isotactic polypropylene (m-iPP) were extruded (in ratios of 75/25, 50/50, and 25/75) from one melt twin-screw extruder to produce three ZN-iPP/ m-iPP polyblended polymers and, subsequently, spin fibers. In this study, we examined the rheology of the ZNiPP/m-iPP polyblended polymers and the thermal characteristics and crystallinity of the ZN-iPP/m-iPP polyblended fibers using gel permeation chromatography, rheometry, differential scanning calorimetry (DSC), wideangle X-ray diffraction, density gradient analysis, and extension stress-strain measurement. The apparent melt viscosity of the ZN-iPP/m-iPP polyblended polymers revealed positive-deviation blends. The 50/50 blend of ZN-iPP/m-iPP had the highest apparent melt viscosity. For five samples, the complex melt viscosity decreased with the angular frequency, which represented typical non-Newtonian behavior. The Cole-Cole plot, which consisted of the imaginary part of the complex melt viscosity versus the real part of the complex melt viscosity plot, of the ZN-iPP/m-iPP polyblended polymers showed a semicircular relationship with the blend ratios. It indicated that the ZN-iPP/m-iPP polyblended polymers were miscible. We analyzed the shear modulus data (G 0 vs G 00 ) by plotting them on a log-log scale. The plot revealed almost the same slopes for the ZN-iPP/m-iPP polyblended polymers, which indicated a good miscibility between the ZNiPP and m-iPP polymers. The experimental DSC results demonstrate that the ZN-iPP and m-iPP polymers constituted a miscible system. The crystallinity and tenacity of the ZN-iPP/m-iPP polyblended fibers initially increased and then fell as the m-iPP content increased. Meanwhile, the 50/50 blend of ZN-iPP/m-iPP had the highest crystallinity and tenacity.

Monitoring nonisothermal crystallization of thermoplastic polymers using a quartz crystal resonator

“…The procedure was also applied for ethylene‐acrylic copolymers and ethylene‐methyl acrylate‐acrylic acid terpolymers,3 polystyrene‐ b ‐poly(ethylene‐ co ‐butene) block copolymers4 and poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends 5. Recently the crystallinity of isotactic polypropylene fiber has been examined by DSC, wide‐angle X‐ray diffraction, density gradient analysis and extension stress‐strain measurement 6. Also, ultrasonic measurement has been used in the characterization of crystallinity, crystallite size and amorphousness 7…”