Addressing Diameter Non-uniformity in the Melt Spinning of Asphaltenes-Derived Carbon Fibres

Abstract

Asphaltenes offer a cheap alternative to the predominant precursor currently used in the manufacture of carbon fibres. Melt spinning is typically employed for transforming asphaltenes into a fibrous form but faces two challenges: inconsistent or poor spinnability and a large diameter variation in the product. This work investigates the diameter variation by separating the variation into a time-dependent component, “relative thinning rate,” and a time-independent component, “fluctuation.” The effects of heat treatment of the asphaltenes precursor prior to spinning near the spinning temperature and delaying the beginning of spinning were explored. Neither methods could completely mitigate thinning but both methods were successful in reducing diameter fluctuation, although delaying the beginning of spinning proved to be more effective. It is suggested that cross-linking and a small amount of cracking could explain results from thermogravimetry and nuclear magnetic resonance. No conclusive trends about the composition, density, and rheology changes with spinning time were observed. The effect of diameter variation on tensile properties was tested but remain inconclusive due to insufficient sample size. Low tensile strengths may also be associated with unoptimized oxidation and carbonization conditions as well as particulate matter that either passed filtration or formed before solidification of the thread line during melt spinning.