Mesophase pitch fibre

The spinning temperature and the type of spinning process also determine the structure of the final carbon fibre. For example, the radial structure of mesophase-pitch fibres is caused by a laminar flow of mesophase pitch through a spinneret and can be suppressed by changing the laminar flow to turbulent flow. Carbon fibres with different structures have been produced using spinnerets of different shapes (Figure 6). 

Rand, B., Carbon fibres from mesophase pitch. In Handbook of Composites, Vol. I Strong Fibres, ed. W. Watt and B. V. Perov. North-Holland, Amsterdam, 1985, pp. 495 575. 

Mochida, I., Yoon, S. H. and Korai, Y., Control of transversal texture in circular mesophase pitch-based carbon fibre using non-circular spinning nozzles, J Mat Sci, 1993,28, 2331 2336. 

Summary of Known Methods of Ereparation of Mesophase. At the time of writing, it appears that a major objective of research into the chemistry of mesophase formation is to obtain mesophase at as low a temperature as possible and to have a soluble mesophase, e.g. in 1,2,4 trichlorobenzene (112). The applications of such mesophase(s) must be in the production of graphitizable pitch fibres. However, this direction of research could have applications in many other areas of carbon/graphite production. Therefore it is appropriate, now, to make a list of known methods of preparation of mesophase (113). 

Fibre manufacture - The conditions for spinning of fibres from mesophase pitch are determined by the pitch rheology which may also influence the degree of preferred orientation. The rheological properties of the spun fibres are important in defining the conditions for thermosetting. 

The relative magnitudes of the Tg values in the two-phase region should be related to the development of microstructure in mesophase pitch, as discussed earlier. Tg will also be a useful parameter in defining the maximum temperature at which fibres can be oxidized without molecular motion causing some decrease in extent of preferred orientation. 

In summary, activated carbon fibres are produced, mainly, by the thermal activation of carbonized (and of course stabilized) carbon fibres. These carbon fibres may have been manufactured for purposes other than as an ACF precursor (like PAN based CF, mesophase pitch based CF) or specifically as a ACF precursor. For most CF precursors, the fibres are produced from direct melt spinning, resulting in the so-called green carbon fibres. These are... 

M. Endo, Structure of mesophase pitch-based carbon fibres, J. Mater. Sci., 23,598-605 (1988). 

Reprinted with permission from Hornby J, Kearsey HA, Carbon fibres from pitch precursors 2. The preparation of mesophase pitches suitable for spinning into fibres, AERE Harwell report AERE-M 3029, Oct 1979. Copyright 1979, AEA Technology pic. 

Figure 7.3 Interfilament sticking or fusing. Source Reprinted with permission from Singer LS, Carbon fibres from mesophase pitch, Fuel, 60(9), 839-847, 1981. Copyright 1981, Elsevier.

Rand B, Carbon fibres from mesophase pitch, Watt W, Perov BV eds.. Strong Fibres, Elsevier Science Publishers, Amsterdam, 495-575, 1985. 

Yoon SH, Takano N, Korai Y, Mochida I, Crack formation in mesophase pitch based carbon fibres. 1. Some influential factors for crack formation, J Mater Sci, 32(10), 2753-2758, 1997. 

Huttinger KJ, Christ K, Carbon fibre reinforced carbon composites produced with mesophase pitches, Naslain R, Lamon J, Doumeingts D eds., European Association for Composite Materials, American Ceramic Soc, Inc., Ceramic Society of Japan, High Temperature Ceramic Matrix Composites, Proc. 5 European Conf. on Composite Materials, Bordeaux, 199-206, Sep 20-24 1993. 

Carbon Fibres from Mesophase Pitch" by B. Rand, in Handbook of Conqiosltes, Vol. 1 - Strong Fibres, W. watt and B. V. Perov, eds. (Elsevier, New York 1985) pp. 495-575. 

At the first view, therefore, a carbon fibre made from mesophase pitch seems to be a contradiction itself. The solution of this problem may be seen in the stabilization treatment of the fibre after spinning which is not only necessary for conservation of the fibre morphology during subsequent heat treatment (the same as with the thermoplastic PAN) but also for crosslinkages between the preformed polyaromatic compounds, by which formation of graphitizing carbon should be inhibited. Thus again, the stabilization treatment in air... 

These properties of carbon fibres from mesophase pitch are very advantageous for carbon/carbon composites (carbon fibre reinforced carbon materials CFRC), which are mostly of military importance today in the missile technology. In spite of intensive studies on further advantageous applications it can not yet be seen where these pitch based fibres are superior for fibre reinforced plastics. Even the present prices do not beat those of PAN based fibres especially if heavy tows are con -sidered. 

---