Simultaneously improving tensile strength and toughness of melt‐spun β‐nucleated isotactic polypropylene fibers

Polymer processing methods generally play a crucial role in determining the development of microstructure in the fabricated product. In this study, isotactic polypropylene (iPP) melt containing 0.05 wt % β-nucleating agent (β-NA) was extruded via a melt flow rate indicator. The molten extrudate was stretched into a fiber upon various take-up velocities (TVs). The microstructures of the fiber were investigated by differential scanning calorimeter, two-dimensional wide-angle X-ray diffraction, and small-angle X-ray scattering. Also, its tensile properties (including tensile strength, modulus, elongation at break, and toughness) were measured by tensile test. Interestingly, the tensile strength (135.0 MPa) of a melt-spun β-nucleated iPP fiber fabricated at 400 cm/min was enhanced by 115.2%, compared with that (62.7 MPa) prepared at 100 cm/min, with a considerable increment in toughness (from 661 to 853 MJ/m3). The enhancement mechanism for tensile properties was discussed based on the microstructures. This work offers a simple approach to prepare β-nucleated iPP fibers with excellent strength and toughness. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43454.