Carbon fibers processing

Fig. 4. Process flow diagrams for (a) PAN-based and (b) pitch-based carbon fiber processes.

The precursor fiber is subsequently washed and stretched to the low tex (denier) required for carbon fiber processing. Stretching also imparts considerable orientation to the polymer molecules and provides the basis for the highly oriented carbon stmcture that forms after carbonization. Special care is taken to avoid contamination or impurities that may form strength reducing flaws in the carbon fiber. 

PAN-based carbon fiber processing flow chart, 26 731. See also Polyacrylonitrile (PAN)... 

Figure 8.6 Flow diagram of carbon fiber processing from a pitch.

Since it is very difficult to find a source of pitch with a consistent batch to batch distribution of molecular types and molecular structural characteristics, then the initial steps of a pitch-based carbon fiber process should "tailor" both the distribution and... 

From this batch procedure, RAE developed a small scale laboratory continuous carbon fiber process to demonstrate feasibility. To provide larger quantities for industrial evaluation, a contract was placed, in 1965, with the Atomic Energy Research Establishment, Harwell, who had existing furnaces that could be readily adapted for this application and... 

The homopolymer PAN is not an easy product to process into carbon fiber, since the initial oxidation stage of the carbon fiber process is a difficult reaction to control due to the sudden and rapid evolution of heat, coupled with a relatively high initiation temperature. This rapid surge of heat can cause chain scission with resultant poor carbon fiber properties. As far as is known, homopolymer PAN has never been exploited as a precursor for carbon fiber manufacture. The exothermic reaction can, however, be adequately controlled by suitable comonomers such as itaconic acid. 

Source Reprinted with permission from Ozbek S, Isaac DH, Carbon fiber processing Effects of hot stretching on mechanical properties, Mater Manuf Process, 9(2), 179-197,1994. Copyright 1994, CRC Press, Boca Raton, Florida. 

Walenta E, Fink HP, Investigation of the thermal oxidative stabilization of PAN filaments in carbon-fiber processing, Acta Polymerica, 41(12), 598-600, 1990. 

In a carbon fiber process, there are three stages where drying may be required ... 

Oxidized PAN fiber is made by a slightly modified first stage of the PAN based carbon fiber process and the properties are listed in Table 20.2. Oxidized PAN fiber, with a density above 1.37 gcm , is non-flammable. 

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