Melt spinning of metallocene catalyzed polypropylenes. II. As‐spun filament structure and properties

Abstract

ABSTRACT:The melt spinning of metallocene catalyzed isotactic polypropylene (miPP) resins was investigated. The as-spun filament properties from six miPP resins were studied with melt flow rates (MFR) between 10 and 100, and a Ziegler-Natta catalyzed isotactic polypropylene (zniPP) resin with a MFR of 35 was studied for a comparison. Generally, as the molecular weight increased the filament density increased, the birefringence decreased, the tensile strength decreased, and the elongation to break increased. As the spinning speed increased, the density, birefringence, tensile strength, and crystalline and noncrystalline orientation functions generally increased. However, the low MFR miPP and the zniPP resin had decreases in the birefringence and tensile strength with an increase of the spinning speed. The miPP resins were found to have breaking tensile strengths up to 50% higher than the zniPP resin at similar spinning speeds. The observed fiber properties were explained based on the nature and orientation of noncrystalline portions of the fibers.

Tensile properties of polypropylene fibres

“…Two processes can be distinguished, depending on the crystallization rate: short spinning (fast crystallization) and long spinning (relatively slow crystallization). At the end of the 20th century, metallocene catalysis allowed the polymer polydispersity to be controlled during its synthesis, leading to an increase in spinning rates and in fibre toughness [49,50]. In short spinning, drawing is mostly performed in the solid state.…”

Structure and Properties of a Metallocene Polypropylene Resin with Low Melting Temperature for Melt Spinning Fiber Application

“…It was found that the density, birefringence, tensile strength, and crystalline and non-crystalline orientation function could be generally improved with increases in the spinning speed. The metallocene iPP fibers were identified to have a breaking tensile strength up to 50% higher than of the Ziegler–Natta iPP fiber at similar spinning speeds [22]. Therefore, developing metallocene iPP for fiber applications may significantly improve the fiber strength and extend their applications.…”