PREPARATION OF CARBON-FIBERS FROM ORGANOSOLV LIGNIN OBTAINED BY AQUEOUS ACETIC-ACID PULPING

Lignin fibers as precursors for carbon fibers were prepared by melt sp inning from organosolv lignin (AWL), which was obtained from birch woo d by aqueous acetic acid pulping at atmospheric pressure and used with out any chemical modification. The spinnability of AWL was attributabl e to polydispersity of the lignin and to partial acetylation of hydrox yl groups during the pulping. Production of satisfactory lignin fibers was achieved by simple thermal treatment of lignin, followed by conti nuous spinning at a rate of more than 400m/min. The thermostabilizatio n of thin (less than 30 mu m in diameter) and thick threads was achiev ed by heating to 250 degrees C at a rate of 0.5 degrees C/min in air a nd under oxygen stream, respectively. Carbonization of thermostable fi bers was achieved by heating to 1,000 degrees C under nitrogen stream. The mechanical strength of the carbon fibers was found to be related to the diameter of fibers. Typical mechanical properties of carbon fib ers from AWL were as follows: fiber diameter 14 +/- 1.0 mu m; elongati on, 0.98 +/- 0.25%; tensile strength, 355 +/- 53 MPa; modulus of elast icity, 39.1 +/- 13.3 GPa. The carbon fibers derived from AWL can be cl assified as fibers of general performance grade.