Study on Crystallization Behaviors and Properties of F-III Fibers during Hot Drawing in Supercritical Carbon Dioxide

Abstract

In order to obtain F-III fibers with high mechanical properties, pristine F-III fibers were hot drawn at the temperature of 250 °C, pressure of 14 MPa, tension of 6 g·d−1, and different times, which were 15 min, 30 min, 45 min, 60 min, 75 min, 90 min, and 105 min, respectively, in supercritical carbon dioxide (Sc-CO2) in this article. All the samples, including the pristine and treated F-III fibers, were characterized by a mechanical performance tester, wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and thermogravimetric analysis (TGA). The results showed that the thermal stability of F-III fibers was enhanced to some extent, and the tensile strength and modulus of F-III fibers had great changes as the extension of treatment time during hot drawing in Sc-CO2, although the treatment temperature was lower than the glass transition temperature (Tg) of F-III fibers. Accordingly, the phase fraction, orientation factor fc of the (110) crystal plane, fibril length lf, and misorientation angle Bφ of all the samples were also investigated. Fortunately, the hot drawing in Sc-CO2 was successfully applied to the preparation of F-III fibers with high mechanical properties.

Supercritical Fluid Processing of Polymers

“…In conclusion, the articles published in this special issue, and reported above, confirmed the interesting peculiarities of supercritical fluids, i.e., SC-CO 2, that allow to improve the traditional processes performance [1,2,3,9] and the characteristics of a large number of polymers [4,5,6,7,8].…”

“…In particular, an innovative SC-CO 2 assisted electrospray process has been proposed for the first time [2], showing promising results in terms of polymeric particles generation, and two different SC-CO 2 assisted techniques (SEDS and SC-foaming) for the generation of polymeric drug-loaded devices have shown interesting results in terms of drug controlled release [1,3], i.e., modifying the processes parameters it is possible to control the specific drug release. Moreover, SC-CO 2 confirmed the capability of improving the mechanical characteristics of several polymers (i.e., polymeric fibers) at specific operating conditions [4,5,6,7,8].…”

“…This special issue currently consists of a total of nine articles written by research groups of experts in the field. The papers can be substantially divided into two main topics:polymeric structure (nanoparticles, microparticles, foams) formation [1,2,3], useful for drug release applications;effects of supercritical fluids on polymer characteristics [4,5,6,7,8]. …”

“…In a related work, Xiaoma et al [6] studied the effect of SC-CO 2 on Aramid fibers (AFs), in particular, on a kind of AFs: F-III fibers. In order to obtain F-III fibers with high mechanical properties, pristine F-III fibers were hot drawn at the temperature of 250 °C, pressure of 14 MPa, tension of 6 g·d −1 , and different times, which were 15, 30, 45, 60, 75, 90, and 105 min, respectively, in SC-CO 2 .…”

Holey Reduced Graphene Oxide Scaffolded Heterocyclic Aramid Fibers with Enhanced Mechanical Performance

“…Aramid fibers are typical high-performance organic fibers [1,2] possessing splendid mechanical properties and comprehensive fibers are putting forward even stringent requirements for their mechanical performances and environmental compatibility. [13] Therefore, many efforts have been devoted to improving the mechanical properties of PBIA fibers. Besides the optimization on polymerization and spinning processes for increasing the crystallinity and orientation degree, [13,14] enhancing lateral interactions between polymer chains are approachable methods by introducing inter-chain hydrogen or covalent bonding.…”