Effect of Different Pressures of Supercritical Carbon Dioxide on the Microstructure of PAN Fibers during the Hot-Drawing Process

Qiao, Mengmeng; Kong, Haijuan; Ding, Xin; Hu, Zhifeng; Zhang, Luwei; Cao, Yanguang; Yu, Miao

doi:10.3390/polym11030403

Cited by 9 publications

(7 citation statements)

References 34 publications

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“…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].…”

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confidence: 66%

“…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]. …”

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confidence: 99%

“…Moreover, as one kind of high diffusion and high heat transfer media, the heat release during the cyclization of PAN fibers could be quickly removed by SC-CO 2 , which achieved the progress of the rapid-entry cyclization reaction. The same authors, in another work [5], studied the effect of different pressures of SC-CO 2 on crystallinity, degree of orientation and mechanical property of PAN fibers during the hot-drawing process. The results showed that as the pressure increased, the crystallinity, and degree of orientation of PAN fibers increased.…”

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confidence: 99%

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Supercritical Fluid Processing of Polymers

Cardea

Reverchon

2019

Polymers

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Supercritical Fluid Processing of Polymers

Cardea

Reverchon

2019

Polymers

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“…Luo studied the surface modification of aramid fiber in scCO 2 with glycidyl-POSS to improve the surface adhesion of aramid fiber/epoxy resin [29]. We reported a method the hot stretching and cyclic reaction of polyacrylonitrile (PAN) fibers in scCO 2 by controlling the temperature and tension to improve the mechanical properties or reduced the heat of the cyclic reaction [20,30]. In our earlier study, we reported a new method improving the mechanical properties of single aramid filament by forming a crosslinking network structure in the amorphous phase of a PPTA fiber with the aid of scCO 2 , which enhanced the amorphous phase and improved the tensile strength and modulus of the fiber [31].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

Kong

2019

Polymers

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High modulus aramid fiber, such as Kevlar 49, is conventionally prepared by the heat annealing of high strength aramid fiber under a suitable tension at high temperature, especially higher than 500 °C. This enables the mobility of a rigid molecule chain to be rearranged into a more perfect crystalline or orientation structure under tension. However, annealing decreases the tensile strength, since the thermal degradation of the molecular chain at high temperature cannot be avoided. Kevlar 49 fibers treated in supercritical carbon dioxide (scCO2) under tension could improve their mechanical properties at a low temperature. The effects of the tension on the mechanical properties and structure of the Kevlar 49 fibers were studied by mechanical testing, wide-angle and small-angle X-ray scattering (WAXS, SAXS), and scanning electron microscopy (SEM). The results show that the mechanical properties, crystallinity and orientation of the fiber can be improved when the tension is less than 0.6 cN/dtex, which may be due to the increasing of the mobility of a rigid segment with the help of the plasticization of scCO2 and re-arrangement of macromolecular chain into crystalline and orientation structure under tension. What’s more, the amorphous region also was enhanced by crosslinking reaction of toluene 2,4-diisocyanate (TDI) with the chain end groups of the macromolecules in the amorphous regions. However, a decrease of tenacity was found when the tension was higher than 0.6 cN/dtex, which is because the tension was so high that the microfibril was broken. The results indicated that treating the Kevlar 49 fiber in scCO2 under a suitable tension with TDI as a crosslink agent can simultaneously improve both the tenacity and modulus of the fiber.

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“…For example, Hobbs et al used the Sc-CO 2 as a reversible plasticizer, transport, and extraction medium to study the crystal annealing of commercial nylon-66, polyethylene terephthalate, and ultra-high molecular weight polyethylene fibers, respectively, during the post-treatment process, which showed that an increase in the modulus and toughness was achieved in nylon-66 [17]. Furthermore, Qiao et al used the Sc-CO 2 to induce the crystallization of polyacrylonitrile fibers, which showed that the crystallinity and mechanical properties of polyacrylonitrile fibers were improved after hot-drawing treatment [18].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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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.

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Effect of Different Pressures of Supercritical Carbon Dioxide on the Microstructure of PAN Fibers during the Hot-Drawing Process

Cited by 9 publications

References 34 publications

Supercritical Fluid Processing of Polymers

Supercritical Fluid Processing of Polymers

Microstructural Changes of Aramid Fiber Due to Reaction with Toluene 2,4-diisocyanate under Tension in scCO2

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

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