Macrostructure and mechanical behavior of fibers of poly-p-phenylene benzobisthiazole

Abstract

SynopsisMorphology and tensile behavior of wet-spun fibers of poly-p-phenylene benzobisthiazole have been investigated. The as-spun fibers contain a large number of voids, which result in void-localized tensile failure. The stress-strain behavior is elastic-plastic with strain hardening. This behavior is shown to be the result of residual stresses which arise during the wet-spinning process.

A model for the compressive buckling of extended chain polymers

“…The longitudinal shear moduli were measured by fiber torsion [5,6,41], and the transverse moduli were measured by lateral compression of the fibers [41,42]. There are no reported values of transverse modulus of PBT fibers, so we estimate a value of U.5 GPa, which is slightly less than that of Kevlar ® .…”

“…The PBT fiber is based on a lyotropic liquid crystalline polymer and exhibits thermal and mechanical properties similar to those of Kevlar ® [6]. All four of these fibers have been shown to develop kink bands under axial compression.…”

“…An example of kink banding in axially compressed Kevlar* fibers is shown in Figure 1. These compressive kink bands have been observed for well-oriented polymers based on both rigid rod [1][2][3][4][5][6] and flexible [7][8][9][10][11][12][13][14][15] chains. Most of these polymers exhibit nearly linear elastic behavior in compression until the onset of kink banding.…”

Structural Investigations of Fibers and Films of Poly(p-phenylene benzobisthiazole). Volume 1

“…PBT fibers spun from MSA solutions contain voids and fracture has been observed to occur at these flaws [17], thus limiting the tensile strength. The effect of processing variables on these flaws will be discussed in Chapter IV.…”

“…The stress-strain behavior of as-spun PBT fibers is decidedly non-linear while heat treated fibers show a linear stress-strain behavior (see Figure 12). The nonlinear behavior in asspun fibers has been attributed to residual stresses occurring due to coagulation [17]. When the skin of the fiber solidifies, the core is still approximately 90% solvent and a 90% volume change is required to form the solid polymer.…”