Pitch materials

Otani, S., Kokubo, Y. and Koitabashi, T., The preparation of highly-oriented carbon fiber from pitch material. Bull Chem Soc Japan, 1970, 43(10), 3291 3292. Otani, S., Watanabe, S., Ogino, H., ligima, K. and Koitabashi, T., High modulus carbon fibers from pitch materials," Bull Chem Soc Japan, 1972, 45(12), 3710 3714. 

This section summarizes the coals used for the project, some of their charactenstics, the preparation of extract and pitch materials, as well as the... 

The thickness and water resistance of the normal air-cured film can now be much improved by the incorporation of suitable coal-tar pitch material. A typical coal tar/epoxy coating material would be constituted as follows ... 

The origins and development of the concept of carbonaceous mesophase, as derived from discotic aromatic nematic liquid crystals, enable applications to be made to industrial processes. The world availability of pitch materials is such that there is an abundance of pitch which produces cokes of little commercial value. A major incentive for research into the Chemistry of mesophase formation is the commercial up-grading of such pitches and the development of specialized pitches. Structure in cokes is described in terms of optical texture. 

Although the great majority of petroleum and coal-based pitch materials, as well as model compounds such as polyvinyl chloride, acenaphthylene, decacyclene and polynuclear aromatic hydrocarbons, form anisotropic graphitizable carbons, it is an almost impossible task to predict the type of optical texture of a coke from an elemental analysis of the pitch. The size, shape and reactivity of peri-condensed polynuclear aromatic molecules in the products of pyrolysis of a pitch play a more important role in determining optical texture. 

The world availability of pitch materials is such that there is an abundance of pitch which produces cokes of little industrial value. The economic pressures within the industry are to upgrade the commercial value of these pitches. Three ways of doing this appear as possibilities - (i) from fractionation separation of pitch systems to select molecular species (a process of "molecular cropping") most amenable to formation of mesophase. (ii) to add, by blending, materials which have been proven to up-grade the quality of resultant cokes. 

Crystallization of Mesophase. As mentioned above, there exists an approach which selects solvent fractions from pitch materials as being suitable for manufacture of carbon artifacts. This is trial and error molecular engineering. If the selected cropped feedstock is suitable then it is possiblej-... 

Industrially available pitch materials are extremely complex chemical... 

Pitch materials may best be characterized in terms of compositions of molecular weight fractions or solubility fractions. 

Pitch materials can be improved with regard to coke quality by ... 

At temperatures above the softening point, isotropic pitch often displays Newtonian flow characteristics (18,19), but this may well depend upon the concentration of any insoluble particles (i.e., primary QI in the case of coal tar based materials) present within the pitch. A high concentration of QI could lead to non-Newtonian character as a result of the particle-particle attractive forces. Figure 3 shows n -T curves for a variety of pitch materials and their pyrolysis products. Pyrolysis increases the Tg of the system and shifts the viscosity-temperature curve to higher temperatures. 

Mesophase Model and the Importance of Alicyclic Structure. The research group at Kyushu University led by Takeshita and Mochida has sought to control the properties of pitch materials by catalytic and co-carbonization techniques. Their progress in these areas may be summarized as follows (i) In earlier work by the... 

Characterization Techniques for Pitch Materials. Among a number of characterization techniques developed in Japan, the technique due to the members of the Society of Heavy Oil, led by Kunugi, stands out as particularly useful. The analytical data are treated by computer methods to construct average molecular structures for the carbonaceous materials. Sanada s group in Hokkaido University used high-temperature NMR and ESR data obtained by in situ measurements of pitch materials in molten salt (21). Much information on mesophase behavior during the heat-treatment process was obtained in this way. 

The mechanical properties as a function of heat treatment temperature are shown in Figure 9 for fibers prepared by the Kyukoshi method. Fiber heat-treated to 2000°C or higher have strengths above 3GPa (435 kpsi) and tensile moduli of the order of 500 GPa (72 Mpsi). The present authors now believe that, in the near future, it will be possible to produce carbon fiber of equivalent properties by selection of suitable raw pitch materials and by development of specialized pretreatment procedures for the pitch to replace the extensive hydrogenation technique described here. 

IR or UV reflecting cholesterics are colorless in the visible region of the spectrum. Therefore, retardation plates can be realized for STN displays using a long pitch material. Also UV reflecting LC siloxanes are of interest for retardation plates because they exhibit behavior like an optical negative uniaxial material. 

Pitch materials appear to be able to meet all four of these criteria. 

Petroleum pitches and coal tar pitches are becoming increasingly important as raw materials for the production of low cost, high performance carbon fibers. This development has been primarily due to the ability of the pitch to form an oriented liquid crystalline mesophase. Since the 1st observation of mesophase spheres in pitch material by Brooks Taylor ( ), a number of studies on the kinetics of mesophase formation have been made by several different groups. 

Since both VPO and GPC rely on the complete solution of the pitch sample, solubility study was performed. Results on a wide range of solvents showed 1.2.4- trichlorobenzene (TCB) to be the best compromize for pitch materials and was chosen for both VPO and GPC. Several solvents such as dlmethylformamlde (DMF), produce low Insolubles. 

Otani S, Yokoyama A, Characteristic chemical constitution of pitch materials suitable for the MP carbon fiber. Bull Chem Soc Japan, 42, 1417, 1969. 

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