Carbonization of Crystalline Polyimide Particles

New carbon particles were prepared from highly crystalline polyimide ones treated at above 600°C. Such particles were obtained by heating polyamic acid solution as the result of thermal imidization of polyamic acids in N-methyl-2-pyrrolidone. The polyimide particles started to thermally decompose from about 500°C and almost finished being carbonized until 1000°C in a yield of 50%. The morphologies of obtained carbon particles were unique like a whisker or coral which had the particle size from 1μm to 5μm, judging from the observation of SEM, and such particles hardly changed at all from the morphology of precursor in spite of extreme decomposing and carbonizing processes. By the treatment at 2800°C, carbon particles from poly (p-phenylene pyromellitimide) were found to be almost graphitized. These had the interlayer spacing d002 of 3.39Å and crystallite thickness of 250Å. It was observed by TEM that the structure of particles like whiskers was made up by stacking of graphite layers, and those layers were turned and closed in a loop at the end of each particle.