Development of high ductility and tensile properties by a two-stage draw of poly(acrylonitrile): Effect of molecular weight

Sawai, Daisuke; Yamane, Akira; Takahashi, Hiroshi; Kanamoto, Tetsuo; Ito, Masayoshi; Porter, Roger S.

doi:10.1002/(sici)1099-0488(199803)36:4<629::aid-polb9>3.0.co;2-j

Cited by 35 publications

(39 citation statements)

References 9 publications

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“…The planar zigzag conformation reported by many authors had a smaller interplanar spacing in the c-axis direction compared with the 3 1 helical conformations. 28 To illustrate this, we calculated the interplanar spacing (d) of different samples by the Bragg equation…”

Section: Resultsmentioning

confidence: 99%

“…With the rising of heat-treatment temperature, the peaks shifted to a higher degree which proved the conformational change of the molecular segment. The planar zigzag conformation reported by many authors had a smaller inter-planar spacing in the c-axis direction compared with the 3 1 helical conformations [28]. To illustrate this, we calculated the interplanar spacing (d) of different samples by the Bragg Eq.…”

Section: Molecular Structural Transformation Of Panmentioning

confidence: 96%

See 1 more Smart Citation

Flexible Reduced Graphene Oxide/Polyacrylonitrile Dielectric Nanocomposite Films for High-Temperature Electronics Applications

Zhang

Lan

et al. 2020

ACS Appl. Nano Mater.

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Polymer dielectrics possess excellent flexibility compared with inorganic ceramic materials.However, the relatively low dielectric constant and working temperature significantly constrains their widespread application. Here, we report a low-cost facile strategy to develop flexible polymer-based composite films with high dielectric constant over a broad temperature.Polyacrylonitrile (PAN) nanofiber mats containing graphene oxide (GO) with core-shell microstructure were firstly prepared via coaxial electrospinning and then hot-pressed into dense composite films. It was revealed that hot-pressing assisted by a stretching force under appropriate temperature and pressure can generate local conformational changes of PAN, leading to the formation of an electroactive phase with increased dielectric constant.Meanwhile, the GO transformed into reduced graphene oxide (rGO) under heat reduction, serving as conductive nanofillers to further promote the increase of dielectric constant.Consequently, the optimized rGO/PAN composites displayed thermally stable dielectric properties with a high dielectric constant (ɛ'=23, 80℃; ɛ'=40, 150℃) and low loss (tanδ=0.13, 80℃; tanδ=0.55, 150℃) over a broad temperature range. This work offers an efficient method for the synthesis of flexible composite dielectric films that hold great potential in high-temperature electronic applications.

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Section: Resultsmentioning

confidence: 99%

Section: Molecular Structural Transformation Of Panmentioning

confidence: 96%

Flexible Reduced Graphene Oxide/Polyacrylonitrile Dielectric Nanocomposite Films for High-Temperature Electronics Applications

Zhang

Lan

et al. 2020

ACS Appl. Nano Mater.

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show abstract

“…That is, spinning dopes made with high molecular weight polymers could be prepared in a spinnable viscosity and processed at a lower solids content than lower molecular weight polymers. Also, high molecular weight polymers, due to the increased length of polymer chains, tended to have higher drawability (45), thus enhancing orientation along the length of the fiber. Low solids content in the spinning solution coupled with increased drawability led to smaller precursor fiber diameters, and as a result, precursor fibers with higher tensile performance.…”

Section: Effect Of Polymer Molecular Weight On As-spun Fiber Propertiesmentioning

confidence: 99%

Synthesis, spinning, and properties of very high molecular weight poly(acrylonitrile-co-methyl acrylate) for high performance precursors for carbon fiber

Morris

Weisenberger

Bradley

et al. 2014

Polymer

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In this paper, synthesis of very high molecular weight (VHMW) polyacrylonitrile-co-methyl acrylate (PAN-coMA) polymers with weight average molecular weights of at least 1.7 million g/mole were repeatedly achieved on a laboratory scale using emulsion polymerization. The development of a hybrid dry-jet gel solution spinning technique for the VHMW PAN-coMA enabled continuous spinning of 100 filament count tows, 100s of meters in length. Single filaments were analyzed and tested for tensile performance. Experimentally, the hybrid spinning method coupled with VHMW polymers produced precursor fibers with excellent tensile properties, averaging 954 MPa in strength and 15.9 GPa in elastic modulus (N = 296), with small filament diameters (5 µm). Results indicate a strong correlation between decreasing filament diameter, facilitated by high molecular weight polymer, and exponentially increasing tensile properties, using a hybrid dry-jet gel spinning process.

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“…In previous papers, , we have shown that gel films of high-molecular-weight at-PAN exhibit high ductility in a two-stage draw, and even PAN has a fairly high chain stiffness and a high cohesive energy density due to the bulky nitrile groups with a large dipole . The maximum achieved total draw ratio (DR t ) and tensile properties increased with sample molecular weight ( M v ) .…”

Section: Introductionmentioning

confidence: 97%

Uniaxial Drawing of Isotactic Poly(acrylonitrile): Development of Oriented Structure and Tensile Properties

Sawai¹,

Yamane²,

Kameda³

et al. 1999

Macromolecules

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Uniaxial drawing of isotactic poly(acrylonitrile) (iso-PAN, isotactic triad fraction of 68%) and the resultant structure and tensile properties of drawn products were studied. The results were compared to those of atactic-PAN (at-PAN). Dried gel films prepared from 2 to 10 wt % solutions in N,N ‘-dimethylformamide were initially drawn by solid-state coextrusion (first-stage draw) to an extrusion draw ratio of 16, followed by a further tensile draw at 100−200 °C (second-stage draw). The ductility of iso-PAN increased rapidly above 100 °C, due to the onset of molecular motion in crystalline regions, as found by WAXD at elevated temperatures. In contrast, the ductility of at-PAN increased above the first-order crystal/crystal transition at around 150 °C. Thus, the temperature for optimum second-stage draw of iso-PAN, 130−140 °C, was significantly lower than that (160−180 °C) of at-PAN, reflecting their crystal softening temperatures. The maximum achieved total draw ratios (DRt), after the two-stage draw, were comparable for these PANs. The shapes of stress/strain curves for highly drawn products recorded at room temperature were significantly different between iso- and at-PAN. The meridional WAXD patterns of these samples revealed that the difference is ascribed to their chain conformations which change with the applied tensile stress. The iso-PAN likely takes a predominantly 3/1 helical chain conformation, whereas at-PAN seems to consist of both planar zigzag and helical sequences, as previously suggested. However, upon increasing the tensile stress on oriented fibers, the helical sequences progressively transform into a planar zigzag conformation which shows a higher modulus. Such an effect of the stress was more prominent in at-PAN than in iso-PAN fibers. Thus, the maximum achieved tensile modulus, as well as the modulus at a given DRt, was slightly higher for iso-PAN than for at-PAN (28.5 ± 1.0 vs 23.0 ± 1.0 GPa). However, the maximum tensile strength at the break was comparable for each PAN, at 0.90 ± 0.05 GPa.

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Development of high ductility and tensile properties by a two-stage draw of poly(acrylonitrile): Effect of molecular weight

Cited by 35 publications

References 9 publications

Flexible Reduced Graphene Oxide/Polyacrylonitrile Dielectric Nanocomposite Films for High-Temperature Electronics Applications

Flexible Reduced Graphene Oxide/Polyacrylonitrile Dielectric Nanocomposite Films for High-Temperature Electronics Applications

Synthesis, spinning, and properties of very high molecular weight poly(acrylonitrile-co-methyl acrylate) for high performance precursors for carbon fiber

Uniaxial Drawing of Isotactic Poly(acrylonitrile): Development of Oriented Structure and Tensile Properties

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