Preparation of carbon fibers from syndiotactic 1,2-polybutadiene

Carbon fibers having good mechanical properties were produced from syndiotactic 1,2-polybutadiene (s-PB). Melt-spun s-PB fibers were made infusible by oxidation, irradiation, or treatments with Lewis acids, protonic acids, or peroxides. The infusibilized fibers were dehydrogenated with oxygen, chloranil, or sulfur and then carbonized. The preparative method by the AlBr₃–sulfur–heat treatment process gave carbon fibers with good mechanical strength in a high yield. A filaments bundle was immersed in a benzene solution of AlBr₃ (2g/100mL) at 42°C for 78 min under tension, washed with methanol, and then immersed in molten sulfur at 275°C for 14 min. After the adhering sulfur was purged with nitrogen at 290°C for 7 min, the bundle was heated up to a temperature of 700–3000°C under tension in a flow of nitrogen or argon for a few minutes. Carbon fibers heated to 1400°C were obtained with the tensile strength of 16.6 t/cm² and the modulus of 1420 t/cm² in a carbon yield of 82% and strain-graphitized fibers at 3000°C with 20 t/cm² and 4010 t/cm² in 70%.