The Interaction between Carbon Fiber and Pitch Measured by High Temperature Electron Paramagnetic Resonance

Abstract

The surface of carbon fiber is one of key properties of composite material with carbon fiber. Interactions between carbon fiber and pitch over the range of carbonization temperature were investigated by in-situ electron paramagnetic resonance (e.p.r.) method.
From in situ e.p.r. measurements for carbon fiber added pitch, the results are summarized as follows: (1) Peak to peak line width of e.p.r. spectra for Si (petroleum pitch derived fiber carbonized at 873K) /Pitch systems and P2 (PAN derived fiber carbonized at 1173K) /Pitch systems was characteristic at the ambient temperature lower than 673K. These characteristics were not influenced by kinds of pitches.(2) Unexpected evidences were found that (i) no obvious differences of the spin concentration between experimental and calculated values for CF/Pitch systems up to 673K, (ii) at the ambient temperature higher than 673K, experimental values of spin concentration were lower than calculated ones. Especially S1/Pitch I (isotropic pitch) and P1 (PAN derived fiber carbonized at 873K) /Pitch A (anisotropic pitch) systems were remarkable.
The spin concentrations depended upon the combination of carbon fiber and pitch.(3) Clear relationship between the spin concentration of carbon fiber added pitch and the degree of graphitization of the carbon fiber was found.