Polymorphism in polypropylene fibers

Abstract

ABSTRACT:The structure of polypropylene fibers formed by different spinning conditions was studied. The investigations were carried out using wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) methods. It was stated that in noncolored fibers the mesophase and the monoclinic ␣ forms were formed. The highest content of the mesophase was observed for fibers extruded at the higher temperature and taken at the medium take-up velocity. In fibers colored with quinacridone pigment the structure containing the monoclinic ␣ and the trigonal ␤ forms was obtained. The highest content of the ␤ form occurred in fibers taken at the lowest take-up velocity. The increase of the take-up velocity caused a rapid drop in ␤ form content. In fibers taken at higher velocities only the ␣ form was formed. It was found that the content of different forms as well lamellar thickness depends on crystallization conditions, which were influenced by the formation parameters.

Elastic constants of lamellar and interlamellar regions in α and mesomorphic isotactic polypropylene by AFM indentation

“…The sharp peaks in 1(d) indicate a large crystalline content. The peak positions, , indicate the presence of the usual α phase and are identical for PH‐3000 and EX‐3000 ( 14°, 16.7°, 18.4°, and 21.4° for the (110), (040), (130), and (111) reflections, respectively).This is in agreement with literature . From these data, the lattice parameters of the α crystal result similar to those reported in the literature and the density is computed to be 0.93 g/cm 3 .…”

“…The crystal phase has three predominant polymorphs which form in specific conditions of pressure and temperature . The monoclinic α polymorph is stable under ambient conditions . iPP crystallizes predominately in the α form during isothermal crystallization and during melt spinning of filaments .…”

“…1 The monoclinic a polymorph is stable under ambient conditions. [2][3][4] iPP crystallizes predominately in the a form during isothermal crystallization 5 and during melt spinning of filaments. 6,7 The b polymorph is obtained upon crystallization in a temperature gradient from a sheared melt, or in the presence of b nucleating agents such as quinacridone pigment.…”

Abstracts

“…14(a)]. Similar transitions for intensity were observed by Broda,46 in pure PP fiber extruded with increasing take‐up speeds. The study concluded the decrease in intensity resulted from the presence of a mesophase coupled with the PP α phase.…”

Influence of processing on structure of β‐nucleated poly(propylene) fibers

“…The crystalline phase in poly(propylene) fibers usually consists of the monoclinic α‐form, the most thermodynamically stable modification commonly encountered in poly(propylene) products. The trigonal β‐form was observed in poly(propylene) fibers by Chen et al10 Our recent investigations revealed that the β‐form can be obtained in the spun poly(propylene) fibers colored with quinacridone pigment spun at low temperature and a very low take‐up velocity 11–13…”