Carbon fiber precursors

Poly(m-phenylene isophthalamide) and other aramids have been proposed as precursor for activated carbon materials. These materials exhibit a very homogeneous nucropore size. This property makes them usable as adsorbents, molecular sieves, catalysts or electrodes. 

Poly(m-phenylene isophthalamide) derived carbon fibers can be activated by carbon vapor deposition of benzene. The activated carbon fibers are suitable as molecular sieves for air separation. Carbon fibers can be obtained from the aramid by pyrolysis at 750-850°C. The pyrolysis may take place in Ar or CO2. 

The fiber may be pre-impregnated with H3PO4. Steam, CO2, and H3PO4 serve as activators. The activation converts the amide groups in the polymer precursor into complex and heterogeneously distributed nitrogen 

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BAKERY PROCESSES AND LEAVENING AGENTS - CHEMICAL LEAVENING AGENTS] (Vol 3) -as carbon fiber precursors [CARBON AND GRAPHITE FIBERS] (Vol 5)... 

Acryhcs and modacryhcs are also useflil industrial fibers. Fibers low in comonomer content, such as Dolan 10 and Du Font s PAN Type A, have exceptional resistance to chemicals and very good dimensional stabihty under hot—wet conditions. These fibers are useflil in industrial filters, battery separators, asbestos fiber replacement, hospital cubical curtains, office room dividers, uniform fabrics, and carbon fiber precursors. The exceUent resistance of acryhc fibers to sunlight also makes them highly suitable for outdoor use. Typical apphcations include modacryhcs, awnings, sandbags, tents, tarpauhns, covers for boats and swimming pools, cabanas, and duck for outdoor furniture (59). 

Carbon and Graphite Fibers. Carbon and graphite fibers (qv) are valued for their unique combination of extremely high modulus and very low specific gravity. Acrylic precursors are made by standard spinning conditions, except that increased stretch orientation is required to produce precursors with higher tenacity and modulus. The first commercially feasible process was developed at the Royal Aircraft Fstablishment (RAF) in collaboration with the acrylic fiber producer, Courtaulds (88). In the RAF process the acrylic precursor is converted to carbon fiber in a two-step process. The use of PAN as a carbon fiber precursor has been reviewed (89,90). 

M. G. Dunham, Stabilisation of Polyacrylonitrile Carbon Fiber Precursors, Ph.D. dissertation, Clemson Urdversity, Clemson, S.C., May 1990. 

The use of a wet-spinning process with inorganic solvents has also been attempted. Although the details of this process are proprietary, it is clear that these inorganic wet-spun PAN fibers make higher quality carbon fiber precursors than those produeed with traditional organic solvents [5]. 

Dunham, M. G., Stabilization of polyacrylonitrile carbon fiber precursors. Ph.D. dissertation, Clemson University, Clemson, SC, 1990. 

Daumit, G. P. and Ko, Y. S., A unique approach to carbon fiber precursor development In High Tech-The PVay Into the Nineties, ed. K. Brunsch et al. Elsevier Science, Oxford, 1986, pp. 201 213. 

Most commercial polymers comprising acrylonitrile (AN) are copolymeric and those containing the highest levels of AN monomer, usually 85 wt% or more, are used in fiber end-uses including carbon fibers, where they are major precursors. As a consequence of their importance as carbon fiber precursors, most of the researches on the thermal degradative and oxidative processes associated with AN copolymers have focused on this area and took place over the 1960-1980 period.26 32 33... 

During the ensuing five years, a number of pitches were developed as carbon fiber precursors through use of various pretreatment techniques (4-9). We explored four basic pretreatment processes, sometimes in combination (a) polymerization and/or... 

The stabilization process is crucial for the quality of the final carbon fiber. Fusion and other damages to the fiber have to be avoided by applying a carefully balanced regime of time and temperature gradient. For most commercial carbon fiber precursor fibers, stabilization is a time-consuming and costly procedure. 

We presently report on a broad search for specific acrylic carbon fiber precursors, which should be stabilized in short time (less than one hour), and yet would give carbon fibers with satisfactory tensile properties. In planning the chemistry of such precursors, it was necessary to take into account the chemical reactions and physical processes going on during the heat treatment. 

Among the features most relevant to carbon fiber precursors, and depending on type and concentration of the comonomer, are solubility, oxygen permeation and melting point depression. 

The stabilization of carbon fiber precursors is done in an air atmosphere, and oxygen is required all through the fiber, for the chemical reactions going on (cf. Sect. 3). 

From Tables 14-17, the AN/VBr (4.2%) fiber, I3x stretched during spinning, emerges as the most promising carbon fiber precursor. It was also found that for this precursor a stabilization with 15% stretching, the temperature profile A (high entrance temperature, cf. Fig. 16), and a residence time of 40 min, leads to carbon fibers with very interesting tensile properties (see Table 17, last entry). For a further reduction of the residence time in the stabilization furnace, the temperature profile needs to be varied... 

A broad screening of carbon fiber precursors, including binary copolymers of AN with a variety of comonomers, terpolymers and blends, in fact confirmed AN/VBr copolymers as the best precursor candidates. 

Developed in the 1940s by DuPont and Union Carbide, PAN began to be used as a carbon fiber precursor material in the 1960s through work done in Japan (Toray) aand Great Britain (Courtaulds). 

Sudo, K. Shimizu, K. Nakashima, N. Yokoyama, A. A new modification method of exploded lignin for the preparation of a carbon-fiber precursor. J. Appl. Polym. Sci. 1993, 48 (8), 1485-1491. 

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