Polyacrylonitrile-based carbon fibres

Figure 11.5. Model of structure of polyacrylonitrile-based carbon fibre (after Johnson 1994).

Three high-strength PAN (polyacrylonitrile)-based carbon fibres (supplied -by Elf Aquitaine France), corresponding to three different stages of manufacturing, were used in this study ... 

Pakalapati et al [115] investigated some carbon/thermoplastic laminates. The materials were pultruded and they consisted of 50 v/o unidirectional continuous polyacrylonitrile-based carbon fibres in DuPont J-2 aromatic polyamide-based thermoplastic matrix. They were subjected to anodic and cathodic currents in sea water. Dynamic mechanical analysis was carried out in situ to measure the shear storage modulus (G ) and shear loss modulus (G") of 1.27mm diameter rod shaped samples, subjected to small amplitude torsional oscillations. The moduli were constant with time in air. 

Johnson JW, Marjoram JR, Rose PG, Stress graphitization of polyacrylonitrile based carbon fibre. Nature, 221, 357-358, 25 Jan 1969. 

Tsai JS. Relationship between two-stage carbonization speeds for polyacrylonitrile based carbon fibre, J Mater Sci Letters, 15(10), 835-836, 1996. 

Figure 12.32 XPS survey spectra of PAN carbon fiber precursors oxidized to (a) 35, (b) 40, (c) 45 and (d) 50 min and finished carbon fiber with an epoxy size. Source Reprinted with permission from Bhardwaj A, Bhardwaj IS, ESCA characterization of polyacrylonitrile based carbon fibre precursors during its stabilization process, J AppI Polym Sci, 51(12), 2015-2020,1994. Copyright 1994, John Wiley Sons Ltd.

Morita K, Murata Y, Ishitani A, Murayama K, Ono T, Nakajima A, Characterization of commercially available PAN (polyacrylonitrile) based carbon fibres. Pure Appl Chem, 58, 456-468, 1986. 

Bhardwaj A, Bhardwaj IS, ESCA characterization of polyacrylonitrile based carbon fibre precursors during its stabilization process, J Appl Polym Sci, 51(12), 2015-2020, 1994. 

Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanofibre reinforced HOPE [52], carbon black filled LDPE-ethylene methyl acrylate composites [28], carbon black filled HDPE [53], carbon black reinforced PP [27], talc filled PP [54], copper particle modified epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon fibre/PC composites [58], PC/MnCli composite films [59], titanocene polyester derivatives of terephthalic acid [60], lithium trifluoromethane sulfonamide doped PS-block-polyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetrafluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon fibre conductive composites [66], carbon nanofibre modified thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon fibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon fibre EVA composites [66], HDPE carbon fibre nanocomposites [52] and PPS [73]. 

Watt W, Chemistry and physics of the conversion of polyacrylonitrile fibres into high modulus carbon fibres. Watt W and Perov BV eds., Vol, Strong Fibres, Elsevier, Amsterdam, 327-388,1985. Johnson W, The structure of PAN-based carbon fibres and relationship to physical properties. Watt W and Perov BV eds., Vol 1, Strong Fibres, Elsevier, Amsterdam, 389-444, 1985. 

The two main processes for making carbon fibres are based on different starting materials, either polyacrylonitrile (PAN carbon fibres) or petroleum and coal tar... 

Mochida, I., Kuroda, K., Kawano, S., Matsumura, Y., Yoshikawa, M., Grulkc, E. and Andrews, R., Kinetic study of the continuous removal of SO, using polyacrylonitrile-based activated carbon fibres. 2. Kinetic model, Fuel, 1997, 76(6), 537 541. 

The production of carbon fibres is based on the pyrolysis of organic fibres or precursors. The main starting materials are polyacrylonitrile (PAN) and pitch (coal tar or petroleum asphalt). They can be classified according to their mechanical performances ... 

A study of the hydrophilic sites on the surface of activated carbon fibres has been made recently by Kaneko et al. (1995) with the aid of X-ray photoelectron spectroscopy (XPS). In this work cellulose (CEL)- and polyacrylonitrile (PAN)-based activated carbon fibres were used and samples were either chemically treated with H202 or heated in H2 at 1000°C. As expected, surface oxidation by the H202 treatment increased the initial uptake of water, while the H2 reduction caused a marked decrease in the amount of water adsorbed at low p/p°. Measurement of the peak areas of the XPS spectra provided a means of determining the fractional surface coverage by the hydrophilic sites. In this way a linear relationship was found between the low-pressure adsorption of water vapour and the number of hydrophilic sites (mainly —COOH). 

The first high-strength carbon fibres were produced in the 1950s (see Donnet and Bansal, 1984). The early carbonized products were rayon-based, but it was soon found that the mechanical properties and the carbon yield could be improved by the use of polyacrylonitrile (PAN) as the precursor. Also, less expensive fibres of somewhat lower strength and modulus could be made from various other precursors including petroleum pitch and lignin. However, cotton and other forms of natural cellulose fibres possess discontinuous filaments and the resulting mechanical properties were consequently found to be inferior to those of the rayon-based fibres. 

In recent years, extensive studies have been undertaken by Kaneko and his coworkers of the properties of activated carbon fibres (ACFs) produced from cellulose, polyacrylonitrile (PAN) and pitch. X-ray diffraction and electron microscopy revealed that the PAN-based and pitch-based fibres had a more homogeneous pore structure than that of the cellulose-based material, although the latter had the largest surface area and pore volume (Kakei et al., 1990). 

When expressed on a volume basis, the uptake of water at high p/p° for both washed and unwashed samples was some 30-35% less than that of nitrogen. A similar variation was noted by Kaneko et al. (ref. 15) for cellulose- and polyacrylonitrile-based activated carbon fibres. The latter chars exhibited hydrophilic character somewhat similar to that reported here for Kevlar -based materials, which these authors attributed to residual nitrogen in the char. 

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