Process for the production of carbon fibers from poly(α(1-→3) glucan) fibers
View Patent ↗A process is provided for preparation of carbon fibers based from fibers of poly(α(1→3) glucan). The method comprises three thermal exposures at progressively higher temperatures to drive off volatiles, thermally stabilize the glucan fiber, and carbonize the thermally stabilized fiber. The carbon fibers prepared according to the process hereof are strong, stiff, tough, and easily handled.
1. A process comprising
subjecting one or more filaments comprising poly(α(1→3) glucan) to a tension below the breaking strength of the one or more filaments at 350° C.;
subjecting the thus tensioned one or more filaments to a first thermal exposure by heating said one or more filaments to a temperature in the range of 160 to 200° C. in air for a duration in the range of 5 to 15 minutes;
subjecting the thus heated one or more filaments to a second thermal exposure by further heating said one or more filaments, still under tension, from a first temperature in the range of 200 to 250° C. to a second temperature in the range of 300 to 350° C., thereby preparing one or more thermally stabilized filaments;
subjecting said one or more stabilized filaments in a zero tension state to a third thermal exposure by heating said one or stabilized filaments to a temperature in the range of 700 to 1500° C. in an inert atmosphere for a duration in the range of 0.5 to 5 minutes, thereby preparing one or more carbonized filaments.
2. The process of claim 1 wherein the first thermal exposure is effected at a temperature in the range of 175 to 185° C. for a duration of 7.5 to 12.5 minutes.
3. The process of claim 1 wherein said second thermal exposure is effected in a series of well-defined steps between the first temperature and the second temperature, with a hold period between steps, and a heating rate from step to step in excess of 10° C. per minute.
4. The process of claim 1 wherein said first temperature is in the range of 230-250° C., and said second temperature is in the range of 310 to 330° C.
5. The process of claim 1 wherein the third thermal exposure is effected at a temperature in the range of 800 to 1000° C. for a duration in the range of 1 to 2 minutes.