High Modulus Fiber Production

The added heat treatment provides an improvement in the orientation of the graphite crystallites, giving carbon fibers with a high YM. 

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Today, carbon fibers are still mainly of interest as reinforcement in composite materials [7] where high strength and stiffness, combined with low weight, are required. For example, the world-wide consumption of carbon fibers in 1993 was 7,300 t (compared with a production capacity of 13,000 t) of which 36 % was used in aerospace applications, 43 % in sports materials, with the remaining 21 % being used in other industries. This consumption appears to have increased rapidly (at 15 % per year since the early 1980s), at about the same rate as production, accompanied by a marked decrease in fiber cost (especially for high modulus fibers). 

The study of thermotropic, as well as of lyotropic LC polymers is directly linked to a series of practical tasks, regarding the construction of polymeric materials with set properties. For instance, making use of anisotropy of the LC state in processing (particularly in moulding) of polymeric materials discloses impressive prospects for the production of so called high modulus fibers and films 18 25). 

In conclusion then, we have synthesized a series of extended-chain, aromatic polyazomethlnes under on-degradatlve conditions. Fusible, tractable polymers were obtained by use of unsymmetrlcally placed substituents, copolymerization, and/or limited proportions of flexible chain units. Many of the polymers yield liquid crystalline melts which were spun Into oriented, high tenacity, high modulus fibers. The fibers were further strengthened by heat treatment. The ease of preparation of the aromatic polyazomethlnes and the outstanding tenacity and modulus range of the fibers make these products excellent candidates for use as reinforcing fibers In resins and rubber. 

The next stage is the carbonization of the oxidized fiber, which is carried out at temperatures from 1,000 to 1,500 °C. This may be followed by graphitization at 2,500 to 3,000 °C for the production of high-modulus fibers. 

Fiber production is a large-volume business around 60 million metric tons per year. About 40% of this is natural fiber cotton and wool the remaining part is man-made , synthetic fiber polyester, polyamide, cellulose, acrylics, and so forth. More than 90% is applied in textiles or carpets. Only about 5% is used in industrial applications. And the new, advanced , high-modulus fibers Technically and commercially very interesting, but we are talking of no more than about 0.2% of the fiber capacity ... 

The mesophase pitches used for high-modulus carbon fiber production can be formed either by the thermal polymerization of petroleum- or coal tar-based... 

In the years following the Brooks and Taylor discovery, many researchers attempted to produce a mesophase pitch suitable for carbon fiber production. Otani et al. [21] were first to report producing a high-modulus carbon fiber from a "specific pitch-like material." The precursor used was tetrabenzophenazine, and thus, the resulting material might be considered a synthetic pitch. 

Control of the regeneration conditions, together with a wide variety of modification, allows the production of a wide variety of products including high-wet modulus fibers, hollow fibers, crimped fibers, and flame-resistant fibers. While almost all rayon is produced using the... 

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