Carbon Fibers Derived from Oleic Acid-Functionalized Lignin via Thermostabilization Accelerated by UV Irradiation

Abstract

Lignin is a biorenewable precursor source suitable for the production of low-cost carbon fibers. In this work, softwood lignin was chemically modified with fatty acids to employ UVtriggered oxidative reactions occurring at long alk(en)yl chains as a pretreatment prior to thermostabilization. The chemical transformation of oleic acid-functionalized lignin (OAFL) under the UV irradiation was the free radical-based cross-linking reaction assisted by atmospheric oxygen, which successfully formed oxidatively cross-linked networks of lignin derivatives at the surface of the fiber. We observed that OAFL showed more rapid oxidative cross-linking than stearic acid-functionalized lignin (SAFL) because the presence of carbon−carbon double bond in OAFL contributed to the formation of more stable allyl radicals in addition to alkyl radicals under the UV irradiation. This UV pretreatment played a pivotal role in the conversion of flexible pristine OAFL fibers into infusible fibers during the subsequent thermostabilization step at the elevation rate of 2 °C/min without melt deformation. As the elevation rate of 2 °C/min is among the fastest thermostabilization process for lignin-derived carbon fibers, the duration of the thermostabilization of the OAFL-derived fibers in this study (∼2 h) is considerably less than previously reported ones. In addition, the UV irradiation process in this study requires less power (150 W) and exposure time (8 min), which can be appreciated by carbon fiber manufacturers aiming to reduce the fabrication cost. Therefore, the chemical functionalization with fatty acids envisages the possibility to produce carbon fibers from lignin precursors via a rapid stabilization step with spending less amount of time and energy.

Recent advances in lignin-based carbon fibers (LCFs): precursors, fabrications, properties, and applications

“…100 Similarly, the addition of nanocrystalline cellulose (NCC) into lignin can also yield LCFs with good fiber geometry through direct carbonization without the stabilization step. 99 Apart from lignin blending with polymers, some interesting methods have also been developed to accelerate the stabilization of LCFs, such as stabilization under HCl/air atmosphere, 124 stabilization assisted by UV radiation, 131 and phosphorus functionalization of lignin. 132 Liu et al prepared a novel precursor of lignosulfonate-acrylonitrile-itaconic acid terpolymer and studied its thermal stabilization.…”

All-Lignin-Based Thermoset Foams via Azide–Alkyne Cycloaddition and Their Fire Resistance after Oxidation

“…Our previous work successfully demonstrated that GPL can be utilized as a versatile starting material to obtain lignin derivatives due to the presence of epoxide rings highly subject to nucleophilic addition reactions. 45 In this study, NaN 3 and carboxylic acids containing carbon−carbon triple bonds (alkynoic acids) reacted with epoxide rings of GPL to introduce azide and alkynoate groups to lignin, respectively (Scheme 1a). As shown in Figure 1a, no absorption bands corresponding to epoxide rings (913 cm −1 ; peak a) were observed from the FTIR spectra of APL, PPL, HPL, and UPL after the ring-opening addition reaction, demonstrating that all ring structures of GPL were opened by nucleophilic addition reactions.…”

“…The synthesis of glycidylated phenolated lignin (GPL) is described elsewhere. 45 Softwood lignin (150 g) and phenol (150 g) were reacted in a closed stainless-steel high-pressure reactor (Parr 4523 benchtop reactor with the model 4848 reactor controller, USA) at 275 °C for 1 h. The mixture was then cooled down to 200 °C, followed by distillation for 1 h under reduced pressure. The resulting solidified phenolated lignin (PL) was ground into a fine powder, which was subsequently rinsed with deionized water on a filter paper until the aqueous filtrate was neutral and dried at 80 °C for 15 h in a vacuum oven.…”

Specific Surface Area Characteristic Analysis of Porous Carbon Prepared from Lignin-Polyacrylonitrile Copolymer by Activation Conditions

“…현재 상업적으로 생산되는 탄소 소재들의 원료 대부분은 화석연료에서 유래한 콜타르, 피치, polyacrylonitrile (PAN) 등이다. 특히 PAN은 가격이 비싸서 이를 재생 가능한 바이오매스로 대체하기 위한 많은 연구가 진행되고 있다 (Sudo and Shimizu, 1992;Kubo et al, 1998;Kadla et al, 2002;Kubo and Kadla, 2005;Ibrahim et al, 2010;Qin and Kadla, 2011;Baker et al, 2012;Chen et al, 2021;Kang et al, 2021).…”

“…Most of the current commercially produced carbon materials nowadays are coal tar, pitch, and polyacrylonitrile (PAN) that are derived from fossil fuels. PANs in particular are expensive, and therefore many studies are being conducted to replace them with renewable biomass (Sudo and Shimizu, 1992;Kubo et al, 1998;Kadla et al, 2002;Kubo and Kadla, 2005;Ibrahim et al, 2010;Qin and Kadla, 2011;Baker et al, 2012;Chen et al, 2021;Kang et al, 2021).…”