Carbon black free radical content

The number of free radicals detected by EPR in porous carbons varies from 10 to 10 radicals per gram and is strongly dependent on the per cent carbon content of the carbon. Likewise in the carbonization of organic materials the number of radicals is strongly dependent on the temperature of carbonization a maximum number of radicals is attained by carbonization between 500 and 600°. Heat treatment of carbon blacks formed by pyrolysis of natural gas and oils also results in a variation 182) of the number of unpaired electrons. 

Figure 25.17 shows that intensity of the narrowest line of the soluble parts of the extract depends on the carbon black content as well as milling time. Concentration of free radicals in NR/carbon black gels was calculated from intensity of the narrowest spectral line and the value is about 4 x 10 sp/g. The results indicate that the quantity of the reactive centres, which is responsible for the formation of the stable gels due to the NR and carbon black interactions, is constant. 

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