CARBON PERGAMON Carbon4l(2003)1399-1409 UV stabilization route for melt-processible PAN-based carbon fibers M. C. Paiva.P Kotasthane. DD. Edie. A.A. Ogale Department of Chemical Engineering, and Center for Advanced Engineering Fibers and Films, Clemson Universit, Clem SC296340910,USA Received 18 January 2003; accepted 29 January 2003 Abstract Ultraviolet radiation-based stabilization routes were explored to produce carbon fibers from melt-processible PAN-based polymers. An acrylonitrile/ methyl acrylate(AN/MA)copolymer was melt-spun into fibers that were crosslinked using UV radiation. The fibers could then be stabilized by oxidative heat treatment, and subsequently carbonized. Physical and mechanical testing was performed to determine the degree of stabilization and the properties of the stabilized and carbonized o 2003 Elsevier Science Ltd. All rights reserved Keywords: A. Carbon fibers; B. Stabilization; C. Differential scanning calorimetry (DSC); Infrared spectroscopy; D. Mechanical properties 1. Introduction thermally-induced reactions occur, other approaches must be developed to crosslink the precursor fibers. In contrast to wet-spinning, the melt spinning techniq Various grades of melt-spinnable pan precursors converts pure precursor directly into fiber form at high currently being developed and evaluated for carbon fiber process speeds and without added expense of solvent production in a joint Clemson/Virginia Tech project ecovery and recycling [1]. However, the bulk of funded by the US Department of Energy. The research fibers are produced from polyacrylonitrile(PAN) team at Virginia Tech is synthesizing melt-spinnable PAN rs that are converted into fiber form by wet copolymers [10], and the team at Clemson is converting spinning methods [2]. The reason behind the use of wet- these into melt-spun PAN and carbon fibers. The present methods is that commercial PAn copolymer aper reports the stabilization procedure developed for rs thermally decompose below their melting tem- these melt-spun PAn fibers as well as the conversion of making melt spinning impossible these stabilized fibers into carbon fibers Recently, BP Amoco Chemicals produced a melt-spinn able PAn copolymer [3, 4] containing a high amount of methyl acrylate comonomer located irregularly along the lymer chain, which most likely decreases the crys- 2. Background: reactions of polyacrylonitrile precursor fibers allinity of the copolymer. A stabilizing agent was also added to inhibit thermal degradation. Although this melt- 2. 1. Heat stabilization of pan spinnable copolymer might appear to be attractive as a carbon fiber precursor, its thermal stability makes standard The stabilization of polyacrylonitrile fibers for carbon oxidative stabilization techniques [1, 5-9 impractica fiber production involves thermal treatment, usually in air, Since this type of PAN copolymer melts before any at temperatures ranging from 180 to 300C. This part of the process is intended to increase the stiffness of the Pan Corresponding author. Fax: +1-864-656-0784 molecules and hold them together in such a way as to E-mail address: ogale clemson. edu(AA. Ogale). avoid extensive relaxation and chain scission during the On leave of absence from the Department of Polymer Engineer- final carbonization step ing, University of Minho, 4800-058 Guimaraes, Portugal The increase in molecular stiffness is mainly achieved 0008-6223/03/s-see front matter 2003 Elsevier Science Ltd. All rights reserved doi:10.1016/0008-6223(03)00041Carbon 41 (2003) 1399–1409 U V stabilization route for melt-processible PAN-based carbon fibers 1 M.C. Paiva , P. Kotasthane, D.D. Edie, A.A. Ogale* Department of Chemical Engineering, and Center for Advanced Engineering Fibers and Films, Clemson University, Clemson, SC 29634-0910, USA Received 18 January 2003; accepted 29 January 2003 Abstract Ultraviolet radiation-based stabilization routes were explored to produce carbon fibers from melt-processible PAN-based copolymers. An acrylonitrile/methyl acrylate (AN/MA) copolymer was melt-spun into fibers that were crosslinked using UV radiation. The fibers could then be stabilized by oxidative heat treatment, and subsequently carbonized. Physical and mechanical testing was performed to determine the degree of stabilization and the properties of the stabilized and carbonized fibers.  2003 Elsevier Science Ltd. All rights reserved. Keywords: A. Carbon fibers; B. Stabilization; C. Differential scanning calorimetry (DSC); Infrared spectroscopy; D. Mechanical properties 1. Introduction thermally-induced reactions occur, other approaches must be developed to crosslink the precursor fibers. In contrast to wet-spinning, the melt spinning technique Various grades of melt-spinnable PAN precursors are converts pure precursor directly into fiber form at high currently being developed and evaluated for carbon fiber process speeds and without added expense of solvent production in a joint Clemson/Virginia Tech project recovery and recycling [1]. However, the bulk of carbon funded by the US Department of Energy. The research fibers are produced from polyacrylonitrile (PAN) precur- team at Virginia Tech is synthesizing melt-spinnable PAN sors that are converted into fiber form by wet and dry copolymers [10], and the team at Clemson is converting spinning methods [2]. The reason behind the use of wet- these into melt-spun PAN and carbon fibers. The present spinning methods is that commercial PAN copolymer paper reports the stabilization procedure developed for precursors thermally decompose below their melting tem- these melt-spun PAN fibers as well as the conversion of perature, making melt spinning impossible. these stabilized fibers into carbon fibers. Recently, BP Amoco Chemicals produced a melt-spinn￾able PAN copolymer [3,4] containing a high amount of methyl acrylate comonomer located irregularly along the 2. Background: reactions of polyacrylonitrile polymer chain, which most likely decreases the crys- precursor fibers tallinity of the copolymer. A stabilizing agent was also added to inhibit thermal degradation. Although this melt- 2 .1. Heat stabilization of PAN spinnable copolymer might appear to be attractive as a carbon fiber precursor, its thermal stability makes standard The stabilization of polyacrylonitrile fibers for carbon oxidative stabilization techniques [1,5–9] impractical. fiber production involves thermal treatment, usually in air, Since this type of PAN copolymer melts before any at temperatures ranging from 180 to 300 8C. This part of the process is intended to increase the stiffness of the PAN molecules and hold them together in such a way as to *Corresponding author. Fax: 11-864-656-0784. E avoid extensive relaxation and chain scission during the -mail address: ogale@clemson.edu (A.A. Ogale). 1 On leave of absence from the Department of Polymer Engineer- final carbonization step. ing, University of Minho, 4800-058 Guimaraes, Portugal. ˜ The increase in molecular stiffness is mainly achieved 0008-6223/03/$ – see front matter  2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0008-6223(03)00041-1