Lignin/Polyacrylonitrile Carbon Fibers: The Effect of Fractionation and Purification on Properties of Derived Carbon Fibers

Abstract

The effects of lignin chemical structures on the quality of lignin-based carbon fibers are still not clear. For this reason, we address the challenge by using a simple acid precipitation method to separate and purify lignin and study the effects of physicochemical characteristics of fractionated lignin on the properties of lignin-based CFs. The precipitation carried out by sequential acidification at different pH levels (10, 8, 6, 4, and 2) is indeed effective in obtaining fractionated lignin samples with different chemical structures, including molecular weights, units’ composition ratios, and polydispersity indexes (PDIs). All the fractionated lignin samples are respectively blended with polyacrylonitrile at the ratio of 1:1 (w/w) and electro-spun into fibers. Results suggest that a fractionated lignin sample with a large molecular weight, low PDI, and strong thermal stability can produce carbon fibers with excellent performance, such as good spinnability, high crystallization, and mechanical strength.

Are lignin-derived carbon fibers graphitic enough?

“…55 High molecular weight lignin (M w : 8170 g mol −1 ) produced carbon fibers with an elastic modulus of 4.5 ± 0.1 GPa, compared to those produced from low molecular weight lignin (M w : 4467 g mol −1 ) which had an elastic modulus of 2.6 ± 0.4. 55 Also, Li et al (2017) developed a method of lignin fractionation using an enzyme treatment and further dialysis to study the effect of molecular weight and polydispersity on the properties of lignin-PAN carbon fibers. 56,57 The elastic modulus values for all lignin-derived CFs increased with molecular weight.…”

Fabrication of polypropylene/lignin blend sponges via thermally induced phase separation for the removal of oil from contaminated water

“…Currently, around 50 million tons of lignin is produced annually as a by-product of the pulp-and-paper industry. Only a small fraction (about 2%) is effectively utilized, and most of the lignin is burned or discharged into rivers, thereby causing serious environmental pollution and grievous waste of renewable resources [24,25]. Lignin gained considerable attention for various applications.…”

Accelerating the formation of the conjugated ladder structure of Poly(acrylonitrile-co-vinyl acetate) by cross-linked poplar lignin doped with boron phosphate

“…Moreover, in conversion of PAN to CF, thermal stabilization takes over 65% of the total energy of conversion [4]. Besides, thermal stabilization takes up to 1120 min for PAN/lignin blends [5] and up to 4530 min for lignin [6]. Therefore, saving energy from thermal stabilization is also required to satisfy the huge demand of low-cost CF.…”