Rheology, mesophase pitch

To date, there has been relatively little work reported on the mesophase pitch rheology which takes into account its liquid crystalline nature. However, several researchers have performed classical viscometric studies on pitch samples during and after their transformation to mesophase. While these results provide no information pertaining to the development of texture in mesophase pitch-based carbon fibers, this information is of empirical value in comparing pitches and predicting their spinnability, as well as predicting the approximate temperature at which an untested pitch may be melt-spun. 

As outlined earlier, the rheological properties of pitch and mesophase pitch are important in the processing of these materials to carbon products. The rheology of isotropic pitch will be considered briefly and then the effects of pyrolysis to mesophase will be described. 

Mesophase Pitch. Mesophase pitch is a generic term for those products of pyrolysis that contain mesophase, or are entirely mesophase, but which on reheating still pass through a fluid phase prior to the formation of semi-coke. The following are areas of scientific or industrial interest where the rheological properties of mesophase pitch are of interest. ... 

The extent to which the mesophase pitch is deformed, as well as the relaxation after deformation, depends on the basic rheological behaviour. 

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. 

Other manufacturing routes for carbon products based on mesophase are almost certain to be devised in the future and will depend upon an understanding of the rheological behaviour of the mesophase pitch. 

Rheological behaviour of chemically stable mesophase-pitch. 

Figure 4.29 The dependency of viscosity on temperature for several isotropic pitches, a mesophase pitch and a typical thermoplastic polymer Ashland 240 (isotropic petroleum pitch) Aerocarb 60 (isotropic pitch distilled from A240) Aerocarb 75 (isotropic pitch distilled from A240) Source. Sumner MB, Thermal properties of heavy isotropic petroleum pitches. Carbon 88, Proceedings of the International Conference on Carbon, University of Newcastle upon Tyne, 52-54, Sep 18-23,1988, Mesophase (produced by pyrolysis of A240) Nylon 6 (a typical melt spur synthetic polymer). Source Reprinted from Whitehouse S, Rand B, Rheology of mesophase pitch from A240. Carbon 88, Proceedings of the International Conference on Carbon, University of Newcastle upon Tyne, 175-176, Sep 18-23, 1988.

Whitehouse S, Rand B, Rheology of mesophase pitch from A240, Carbon 88, Proceedings of the International Conference on Carbon, University of Newcastle upon T5me, 175-176 Sep 18-23, 1988. 

F.F. Nazem, "Rheology of Carbonaceous Mesophase Pitch," Fuel, 59, 851-858 (1980). 

The Pitch-Mesophase-Coke Transformation As Studied by Thermal Analytical and Rheological Techniques... 

Coalescence of mesophase is often said to be determined by the mesophase viscosity. This aspect requires much further investigation. However, it is clear that, amongst other factors, the rheological behaviour (including viscoelastic effects) of each phase is important in mesophase growth and coalescence. Diffusion of molecular species through the isotropic pitch to the mesophase spheres is likely to be related to the viscosity of the isotropic med i urn. 

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