Solvent-extracted pitch precursors

Solvent-Extracted Pitch Precursors for Carbon Fiba ... 

Pitch is a "pseudo solution" of a wide variety of different generic classes of hydrocarbons ranging from paraffins at one extreme to very highly aromatic species at the other. By using the Theory of Solubility for Non-Electrolytes, specific fractions can be isolated from a pitch by properly selecting a solvent system and extraction conditions. "Tailored" precursors for carbon fiber and other carbon products, such as carbon/carbon matrices and bulk graphites, can thus be obtained. The technique of extraction, the characteristics of different precursors, and the structure and properties of carbon fiber and composites made from solvent extracted precursors will be discussed. 

The carbonized fibers from the solvent extracted pitch precursor described in the previous section generally exhibited textures similar to those shown in Figures 9a-b. Radial textures predominated, although random textured fibers and hybrids (random/radial) were occasionally found. Fiber splits (or missing wedges) were rarely observed. The final texture obtained in the fibers was found to be a... 

With regard to pitch-based carbon fiber, solvent extracted pitches show excellent potential as a precursor for high quality fiber. 

An isotropic pitch precursor is used to make a GP grade carbon fiber, whilst a mesophase pitch will produce a HP carbon fiber that can, if necessary, also be made from the same grade of isotropic pitch feedstock. Mesophase pitches can be divided into classes (Chapter 4) on the basis of their method of manufacture—preparation by means of pyrolysis, solvent extraction, hydrogenation or catalyst modification. A variant of the hydrogenation proeess, termed the Dormant Process, will produce a carbon fiber which is intermediate between GP and HP, with high elongation [1]. 

An Exxon cat cracker bottom pitch was extracted with solvents of varying solubility parameter in order to evaluate the relationships which exist between extraction conditions and the characteristics of the extracted product. The precursor pitch possessed a carbon/ hydrogen ratio of 1.49 and a alculatedO, overall average solubility parameter of 10.48 reflux quinoline insolubles content of the pitch was 2.3% and the refluxing toluene insolubles were at a level of 20.3%. The pitch was not optically anisotropic. Upon heating in N2 to 530 C in a TGA, a coke yield of 37% was obtained. 

VARIATION IN CARBON FIBER MODULUS AS A FUNCTION OF CARBONIZING TEMPERATURE. PRECURSOR WAS A CAT CRACKER BOTTOM PITCH EXTRACTED WITH A SOLVENT HAVING A SOLUBILITY PARAMETER OF 8. -... 

In 1984, DuPont acquired the Exxon pitch based carbon fiber business and it was highly probable that the DuPont fibers were based on the Exxon patents [58] using a neophase pitch, which had been extracted with solvent, as precursor material. Initial studies revealed an oriented core microstructure [59]. Later work showed E130 to have an oriented core [60], or radial [61], but all workers agreed that there were many disclinations, which is consistent with the low graphitizability of the fiber. Kogure, Sines and Lavin [61] are insistent that... 

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