Two-step chemical conversion of coal tar pitch to isotropic spinnable pitch

The traditional techniques for preparing spinnable pitch from coal tar pitch are air blowing or thermal treatment. A new method to produce isotropic spinnable pitch has been developed. In this method, a commercial almost free of quinoline insoluble (almost QI-free) coal tar pitch was firstly air blown in the temperature range of 280 to 320 °C. Air blowing increases the softening point of the pitch without destroying its spinnability. Next, a thermal treatment between 350 and 380 °C was applied and this increased the softening point to 280 °C. The effects of processing parameters such as treatment time and temperature for air blowing and thermal treatment on the characteristics of the spinnable pitch were studied. The spinnable pitch obtained by the two-step technique exhibited a high softening point (280 °C), a high coking value (82%). The green fibers spun from the pitch, showed uniform diameters (19 ± 1 μm) with smooth and homogeneous surfaces. The green fibers were then stabilized at 320 °C for 1 h and further carbonized at 1000 °C for 1 h in nitrogen. The obtained carbon fibers also had smooth surfaces and homogeneous diameters (17 ± 1 μm).