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Synthesis of Modified Polyacrylonitriles and Their Conversion into Carbon Fibres I. Copolymers Containing Carbonyl Groups.
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND)
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Possible routes for synthesizing the copolymer - CH2CHCNn-COCHCN- were examined since -COCHCN- units are probably a major constituent of polyacrylonitrile PAN fibres oxidized for the production of high modulus carbon fibres. No suitable method was found. Copolymers of acrylonitrile with a acrylic acid and b acrylamide were prepared and spun into fibre for evaluation as carbon fibre precursors. The Youngs moduli of the carbon fibres produced from the unoxidized precursors were similar to those obtained from unoxidized PAN fibres, indicating that the comonomers had not given rise to any additional cross-linking during pyrolysis. However, an 81 acrylonitrile acrylic acid copolymer fibre oxidized for only 2 h at 220 C gave carbon fibres with a modulus of 172 GPa after carbonizing to 1000 C, i.e. only 7 lower than the modulus of fibres obtained by carbonizing oxidized commercial PAN fibre. This may have been due to the -CO2H groups accelerating the rate of PAN cyclization as fibre of this diameter, viz.20 micrometers, normally requires about 20h oxidation at 220 C. Author
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