Crystallite size and shape in Twaron fibers heat treated at different temperatures using WAXS

Abstract

ABSTRACT:We have determined the crystallite size of Twaron fibers heat treated at various temperatures by analyzing the wide angle X-ray scattering (WAXS) data employing a profile analysis technique developed by us. This study indicates that the differential change of size with temperature is less than 1% of the mean value along both (110) and (200) directions. Hence, these fibers are thermally stable and thermal aging is negligible. We have also observed that the lattice strain variation with temperature is negligible. These studies demonstrate the thermal stability of fibers in terms of the changes in the microcrystalline parameters.

Effect of thermally induced microstructural changes on the mechanical properties and ballistic performance of poly (p-phenylene terephthalamide) fibers

“…It is also well noted (in Figure 2(d) and (e)) that a considerable 48.95% reduction in crystallinity is observed at 130°C for 0.9% increase in dimension along a-length, while 0.7% increase in a-dimension brings about 46.89% reduction in crystallinity at 80°C. The similar thermally induced changes in crystallinity are also reported in other studies 16,25,[30][31][32] for Nomex and different grades of PPTA fibers. It indicates that changes in unit cell adimension, even at a small scale, can account for a significant reduction in crystallinity and thus behaves as an important crystallographic parameter upon prolonged thermal induction.…”

Facile preparation of aramid nanofibers from Twaron fibers by a downsizing process

“…3a shows an SEM image of Twaron ber, which is made up of aggregate of aramid microcrystals with a crystallite size of approximately a dozen nanometers. 9 To atomize the aggregates, the Twaron was passed through high-pressure water atomization equipment with 1 wt% concentration. Aer 30 cycles of mechanical treatments, the Twaron ber was not disintegrated at all even though the system applied a super-high-pressure water jet of 200 MPa (Fig.…”

“…8 Therefore, aramid bers are of high strength and high Young's modulus, with good thermal stability and high impact resistance; they are used in automotive, construction, sporting, aerospace, and military applications. 9 These characteristics are the result of a 100% paracrystalline structure with molecular chains preferentially oriented along the ber axis caused by the process of spinning lyotropic liquid crystal. 10 Nanobers from Twaron would offer useful application as a novel high-performance material.…”