Isotropic pitch-based carbon fibers

Isotropic fibrous materials, 11 176-177 Isotropic microporous membranes, 15 798 Isotropic moldings, 23 397 Isotropic pitch-based carbon fibers, 26 734-735... 

PAN-based carbon fibers Isotropic-pitch-based carbon fibers... 

Characterization of Pore Distribution in ACF Prepared from Isotropic Pitch-Based Carbon Fiber... 

Rayon-based carbon fibers, on the other hand, have low thermal conductivity and are, therefore, used for thermal insulation purposes. Examples include the nose cone and leading edges of the U S Space Shuttle Orbiter. Isotropic pitch-based carbon fibers are also used for insulating purposes because of their low thermal conductivity. 

As we can observe in Table 4, the results agree with those obtained by other authors However, we have not observed the shortest lifetime, probably due to the small size of the graphite microcrystals existing in isotropic pitch-based carbon fibers. 

In carbon fiber felts, however, only one kind of pores, interparticle pores, are observed among the fibers (Fig. 27.4). The surface of each fiber is smooth and no pores are inside of the fibers. Felts composed of polyacrylonitrile (PAN)-based and isotropic pitch-based carbon fibers were used as sorbents in the present work. 

ISOTROPIC PITCH BASED CARBON FIBERS are CARBON FIBERS obtained by CARBONIZATION of isotropic pitch fibers after these have been stabilized (i.e. made non-fusible). LAMP BLACK is a special type of CARBON BLACK produced by incomplete combustion of a fuel rich in aromatics that is burned in flat pans. LAMP BLACK is characterized by a relatively broad particle size distribution. 

Certain pitches can be spun directly into isotropic pitch fibers with only minor devolitization. Carbonized isotropic pitch fibers cannot be graphitized and develop mechanical and thermal properties that are substantially inferior to those produced by other precursors. However, isotropic pitch fibers are very inexpensive and have found commercial applications in areas that do not require the exceptional mechanical and thermal properties of mesophase pitch-based carbon fibers. Isotropic pitch-based carbon fibers are used in filters, brake pads, activated carbons, and as substrates for chemical vapor deposition (23). Table 3 summarizes properties of isotropic pitch-based carbon fibers. 

Table 3. Properties of Isotropic Pitch-Based Carbon Fibers ...

Isotropic pitch-based carbon fibers are carbon fibers obtained by carbonization of isotropic pitch fibers after these have been stabilized (i.e. made non-fusible). 

During fabrication o/isotropic pitch-based carbon fibers no means (neither mechanical nor chemical) are applied to achieve preferred orientation of the polyaromatic molecules in the fiber direction. They belong to the carbon fibers type LM, and because of the relatively low values of strength and Young s modulus this pitch-based carbon fiber type is not used for high-performance reinforcement purposes. 

The term pitch-based carbon fibers comprises the isotropic pitch-based carbon fibers as well as the anisotropic MPP-based carbon fibers. The isotropic type belongs to the carbon fibers type LM and is mainly used as filler in polymers and insulation materials and for similar applications. The anisotropic type (MPP-based carbon fibers) belongs to the carbon fibers type HM and is used mainly for reinforcement purposes due to its high Young s modulus value. 

See carbon fibers type HM, carbon fibers type LM, isotropic pitch-based carbon fibers, MPP-based carbon fibers... 

Park, S. H., C. Kim, Y. I. Jeong, D. Y. Lim, Y. E. Lee, and K. S. Yang (2004a). Activation behaviors of isotropic pitch-based carbon fibers from electrospinning and meltspinning. Synthetic Metals 146(2) 207-212. 

It has been more than 50 years that carbon fibers have been under development from rayon, polyacrylonitrile (PAN), isotropic and mesophase pitches. PAN-based technologies are most commercial production of carbon fibers and rayon-based carbon fibers are no longer in production. Pitch-based carbon fibers currently account for niche markets. Isotropic pitch-based carbon fibers have modest level of strength and modulus and are the least expensive carbon fibers. PAN and mesophase-based carbon fibers heat treated to improve modulus. Both PAN and mesophase pitch-based carbon fibers are not subject to creep or fatigue failure and set them apart from other material which is critical for application such as tension leg platforms for deep sea oil production [201]. The new generation of carbon based fibers is carbon nanotube (single and multi-walled). There are different synthesis methods for carbon... 

The effect of mesophase pitches on the tensile modulus of the resultant pitch based carbon fiber has been studied [245] and carbon fiber prepared from an isotropic pitch containing mesophase spheres has also been studied [246],... 

The torsional modulus is shown in Figure 20.22 and appears to be governed by the structure of the microsection increasing in the order— mesophase pitch based carbon fiber < rayon based carbon fiber < isotropic pitch based carbof fiber < PAN based carbon fiber. 

Pitch as a precursor material is cheaper than PAN as a precursor fiber, but the conversion of pitch into mesophase pitch and subsequent fiber formation is complex and costly. When a pitch is not transformed into a mesophase and is spun as an isotropic liquid, the resulting carbon fibers have extremely poor mechanical properties. These considerations explain why more than 90% of today s carbon fibers are fabricated from PAN based precursors. Processes for fabricating carbon fibers from PAN or pitch based precursor fibers differ in important aspects, but also share important commonalties (Figure 2). Finally, the carbon yield from PAN based precursor fibers is 50%, that from mesophase pitch is 70-80%, and that from rayon is 25%. 

Mesopitch based carbon fibers exhibit a variety of microtextures depending on the structure of the specific precursor fiber and the spinning conditions. Mesopitch based fibers prepared from 100% mesophase pitch have a more homogeneous microtexture than those prepared from mixtures of anisotropic and isotropic pitches. Further, disturbing the flow pattern of the... 

Note RAYON-BASED CARBON FIBERS have a more isotropic structure than similarly heat treated polyacrylonitrile (PAN) or MESOPHASE PITCH (MPP) BASED CARBON FIBERS. Their Young s modulus values are, therefore, drastically lower (< 100 GPa). RAYON BASED CARBON FIBERS can be transformed into anisotropic CARBON FIBERS with high strength... 

Figures 1.6a and 1.6b present the Nj isotherms for ACs prepared using two types of carbon fiber (CF) precursors [88,98] (1) anisotropic PAN-based carbon fibers from Hexcel, and (2) isotropic coal tar-pitch-based fibers from Donac. It...

The term carbon fibers type LM is sometimes used for various types of isotropic carbon fibers known as pitch-based or rayon-based carbon fibers that have not been subjected to... 

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