Microfibril alignment induced by stretching fields during the dry-jet wet spinning process: Reinforcement on polyacrylonitrile fiber mechanical properties

Gao, Quan; Jiang, Min; Chen, Mei‐Ling; Zhao, Shengyao; Wang, Wenli; Qin, Jianjie; Wang, Chengguo

doi:10.1016/j.polymertesting.2019.106191

Cited by 22 publications

(21 citation statements)

References 43 publications

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“…Moreover, the change in the lattice parameter ratio reveals the microstructural change in the orthorhombic unit cells to the tetragonal unit cells as the macroscopic tensile strain of PANF increases. The material properties of drawn fibers are highly dependent on the processing temperature and drawing ratio; high temperature and high drawing ratio are preferable owing to the enhanced chain mobility and improved crystalline orientation [ 97 , 98 , 99 ]. The drawing effects on the microstructural changes and mechanical property improvements have been demonstrated with the dry-jet wet spinning process [ 100 , 101 ].…”

Section: Spinning Processmentioning

confidence: 99%

Designing Materials and Processes for Strong Polyacrylonitrile Precursor Fibers

2021

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Although polyacrylonitrile (PAN)-based carbon fibers have been successfully commercialized owing to their excellent material properties, their actual mechanical performance is still much lower than the theoretical values. Meanwhile, there is a growing demand for the use of superior carbon fibers. As such, many studies have been conducted to improve the mechanical performance of carbon fibers. Among the various approaches, designing a strong precursor fiber with a well-developed microstructure and morphology can constitute the most effective strategy to achieve superior performance. In this review, the efforts used to modulate materials, processing, and additives to deliver strong precursor fibers were thoroughly investigated. Our work demonstrates that the design of materials and processes is a fruitful pathway for the enhancement of the mechanical performance of carbon fibers.

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Section: Spinning Processmentioning

confidence: 99%

Designing Materials and Processes for Strong Polyacrylonitrile Precursor Fibers

2021

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“…Increasing the TDR during the spinning process increases the orientation along the fiber axis [15], increases the crystallinity [16] and the homogeneity [17], and promotes the formation of a rounded cross-section [18]. Surface roughness also increases with drawing [19,20], which must be accounted for when considering its properties in the transverse direction. A well-drawn fiber results in superior tensile properties, such as increased tensile strength and tensile modulus [13,15,18,21,22].…”

Section: Introductionmentioning

confidence: 99%

Improving Transverse Compressive Modulus of Carbon Fibers during Wet Spinning of Polyacrylonitrile

Wong

Hillbrick

Kaur

et al. 2022

Fibers

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The performance of carbon fibers depends on the properties of the precursor polyacrylonitrile (PAN) fibers. Stretching of PAN fibers results in improved tensile properties, while potentially reducing its compressive properties. To determine optimization trade-offs, the effect of coagulation conditions and the stretching process on the compressive modulus in the transverse direction (ET) was investigated. A method for accurately determining ET from polymer fibers with non-circular cross-sectional shapes is presented. X-ray diffraction was used to measure the crystallite size, crystallinity, and crystallite orientation of the fibers. ET was found to increase with decreasing crystallite orientation along the drawing direction, which decreases the tensile modulus in the longitudinal direction (EL) proportionally to crystallite orientation. Stretching resulted in greater crystallite orientation along the drawing direction for fibers formed under the same coagulation conditions. Increasing the solvent concentration in the coagulation bath resulted in a higher average orientation, but reduced the impact of stretching on the orientation. The relationship between ET and EL observed in the precursor PAN fiber is retained after carbonization, with a 20% increase in ET achieved for a 2% decrease in EL. This indicates that controlled stretching of PAN fiber allows for highly efficient trading off of EL for ET in carbon fiber.

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“…Polyacrylonitrile (PAN)-based carbon fibers are utilized in many applications in automobile, sports, aviation, wind blades, and pressure vessels, and their demand increases very quickly. − They are manufactured by PAN precursor fibers through the thermal stabilization and carbonization. − And their mechanical strength is determined by the quality and microstructures of precursor fibers, which are originated and developed during the stretching process of fiber production. − So far, PAN precursors are prepared by wet spinning, dry-jet wet spinning, and gel spinning. , The fiber-processing conditions have a vital influence on the fiber microstructures and the quality of precursor fibers. , Many studies have been carried out to reveal the evolution mechanisms of PAN fiber microstructures, thereby regulating and controlling microstructures of PAN fibers by optimizing process parameters to achieve excellent mechanical properties. ,, However, with either technique, the coagulation process is an initial and vital stage for structural formation of the PAN fibers, which determines the quality of PAN fibers and then affects the properties of the carbon fibers. − Consequently, we have devoted to explore the formation mechanisms of the PAN fiber microstructures during the coagulation process in this work as well as in previous works. , …”

Section: Introductionmentioning

confidence: 99%

“…PAN fibers possess a complex hierarchy of the multiscale structural feature, such as skin-core structures, porous structures, defects, crystal structures, oriented molecules, and microfibrils. − Especially, the microfibrils are supposed to be the fundamental superstructure elements of PAN fibers. − These microfibrils with diameters in the range of 10–100 nm, form the fibrillar bundles, and ultimately make up the full fiber measuring 10 s of micrometers in diameter . In PAN precursor fibers, they are composed of aligned and oriented microfibrils that are superimposed by fold-chain crystal layers . However, PAN nascent fibers are constituted of a random microfibrillar network. , Meanwhile, the lamellae structures perpendicular to the fiber axis are also discovered in PAN nascent fibers in electron microscope studies .…”

Section: Introductionmentioning

confidence: 99%

From Microfibrillar Network to Lamellae during the Coagulation Process of Polyacrylonitrile Fiber: Visualization of Intermediate Structure Evolution

et al. 2020

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Coagulation process is one of the most important stages of the microstructure formation and evolution in polyacrylonitrile (PAN) fibers during the spinning process. The network and lamellae were fundamental superstructures of PAN nascent fibers. Nevertheless, due to complex phase transitions, the mechanism of the microstructure formation and evolution in PAN nascent fiber was not comprehensively elucidated yet. In this work, a full account of microstructure formation and transformation of PAN nascent fiber by electron microscopic analysis was presented and the underlying mechanism of their formation and transformation during the coagulation process was proposed. During the coagulation process, phase separation, gelation, crystallization, and concentration fluctuations occurred. The densified and elongated domains of the polymer-rich phase were solidified into the microfibrils, and they were cross-linked to form the microfibrillar network. The transverse domains induced by the concentration fluctuation acted as the precursors of the lamellae, and subsequently the lamellae were stacked closely and regularly. Meanwhile, crystallization occurred along the whole process, and the crystal layers formed and aggregated within the microfibrils. Our work therefore revealed the existing morphological types in PAN nascent fibers and their underlying formation mechanism.

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Microfibril alignment induced by stretching fields during the dry-jet wet spinning process: Reinforcement on polyacrylonitrile fiber mechanical properties

Cited by 22 publications

References 43 publications

Designing Materials and Processes for Strong Polyacrylonitrile Precursor Fibers

Designing Materials and Processes for Strong Polyacrylonitrile Precursor Fibers

Improving Transverse Compressive Modulus of Carbon Fibers during Wet Spinning of Polyacrylonitrile

From Microfibrillar Network to Lamellae during the Coagulation Process of Polyacrylonitrile Fiber: Visualization of Intermediate Structure Evolution

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