Fibers from Pitch Fiber spinning

When producing carbon fibers from pitch, a critical processing parameter is the viscosity of the pitch, which is extremely dependent on the spinning temperature. If pitch was a truly Newtonian fluid, the viscosity would be independent of shear rate, attaining its value almost instantaneously. It would be expected that the ratio of the hot filament diameter to the orifice diameter (die swell ratio) would be less than 1.1 and the molten fluid would not climb the stirring rod (the so called Weissenberg effect) [228]. 

Elongational behavior is induced in the entrance of the spinning hole and in the transition region from backhole to actual capillary. In practice hardly any permanent orientation is built up in this way, however, because molecular relaxation is rapid. Spinning hole profiles are smoothened only to prevent the formation of vortices which would lead to extrudate distortion. Promoting orientation already in the spinning holes is not common for melt spinning. It could be beneficial for the orientation of melt-spun liquid-crystalline polymers, however, for example in the production of carbon fiber from pitch. 

In order to produce carbon fibers from polyacrylonitrile) (PAN) and various pitches, stabilization is essential after the spinning, which consists of a chemical reaction using different oxidizing gases, such as air, oxygen, chlorine, hydrochloric acid vapor, etc. [91]. The stabilized fibers are then... 

High-Performance Carbon Fiber (HPCF) from Hydrogenated Pitch. Alicyclic molecular structure and the extent of hydrogen transfer between molecules have been progressively recognized as important factors to control the properties of the precursor pitch for fiber spinning. Three experimental methods of pitch preparation were explored as our understanding of pitch chemistry was developed. 

High modulus C-fibers from special pitch 1st step polymerization > 300 C to mcsophase pitch 2nd step melt spinning 3rd step oxidative crosslinking 4th step inert carbonization at 1500 to 3000"C... 

MESOPHASE PITCH BASED CARBON FIBERS (MPP BASED CARBON FIBERS) are CARBON FIBERS obtained from MESOGENIC PITCH after it has been transformed into MESOPHASE PITCH (MPP) at least during the process of spinning, after the spun MESOPHASE PITCH fibers have been made non-fusible (stabilized) and carbonized. 

Mesophase pitch fibers are produced through melt spinning that is essentially the same as that used to spin commercial polymers. Figure 13 shows this process in which an extruder melts pitch particles and pumps the molten pitch through a multiholed spinnerette. The high extensional shear orients the liquid crystalline mesophase molecules as it approaches and flows through the spinnerette. The flbers emerging from the spinnerette are drawn by a windup spool. 

The melt-spinning process used to convert mesophase pitch into fiber form is similar to that employed for many thermoplastic polymers. Normally, an extruder melts the pitch and pumps it into the spin pack. Typically, the molten pitch is filtered before being extruded through a multi-holed spinnerette. The pitch is subjected to high extensional and shear stresses as it approaches and flows through the spinnerette capillaries. The associated torques tend to orient the liquid crystalline pitch in a regular transverse pattern. Upon emerging from the... 

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