Synthesis and Characterization of Epoxy Thermosetting Polymers from Glycidylated Organosolv Lignin and Bisphenol A

A simple and rapid synthesis of biobased epoxy resin derived from vanillyl alcohol was performed, and its chemical structure was confirmed by FTIR and 1H and 13C NMR spectroscopies. Vanillin-based epoxy resin (VE) was further reinforced by lignin-containing cellulose nanofibrils (LCNFs) with different weight ratios. Characteristics of the resin and the nanocomposites, including the curing process, chemical structure, morphology, mechanical performance, thermo-mechanical properties, and thermal degradation behavior, were studied. A significant improvement in the mechanical performance of the nanocomposites was achieved with a low level of nanofibril addition. Tensile strength and toughness increased by 81% and 185%, respectively, when 1 wt % of LCNFs were used. The nanocomposite also showed an increase in thermo-mechanical properties as measured by dynamic mechanical analysis (DMA) and increased resistance to thermal degradation as shown by higher onset temperature and final char value in thermogravimetric analysis (TGA). This study showcased a promising approach to make environmentaly friendly sustainable biobased epoxy products with superior performance.

Section: ■ Results and Discussionmentioning

confidence: 99%

Biobased Epoxy Synthesized from a Vanillin Derivative and Its Reinforcement Using Lignin-Containing Cellulose Nanofibrils

Wang

Gnanasekar

Nair

et al. 2020

“…For example, mixtures of lignin-derived substituted phenols have been used in epoxy resins and block polymers , to tune and enhance material properties, such as the glass transition temperature ( T g ), solvent resistance, and adhesion strength. Additionally, lignin-derived polyaromatics, including bisguaiacols, have shown promise in thermoset and thermoplastic applications currently dominated by petrochemicals, e.g., bisphenol A (BPA). ,− …”

Section: Introductionmentioning

confidence: 99%

Potential Lignin-Derived Alternatives to Bisphenol A in Diamine-Hardened Epoxy Resins

Nicastro

Kloxin

Epps

2018

118

This work details the synthesis and characterization of potentially lignin-derived bisguaiacols as alternatives to petroleum-derived bisphenol A (BPA) in diamine-cured epoxy resins. The variations in the number of methoxy groups of lignin facilitate the systematic chemical and thermomechanical manipulation of bisguaiacol-based thermosets to achieve desirable properties. Herein, ten bisguaiacols (including structural isomers), differing in the number of methoxy groups and regioisomer content, were synthesized from substituted bioderivable hydroxybenzyl alcohols and phenols by acidcatalyzed electrophilic aromatic substitution approaches and then functionalized with oxirane groups. These bisguaiacol diglycidyl ethers were subsequently cured with a model diamine. All cured bioderivable resins had glass transition temperatures (T g 's) above 100 °C, 5 wt % loss temperatures above 300 °C, and room-temperature glassy storage moduli above 2.0 GPa, values that were comparable to bisphenol A diglycidyl ether (BADGE/DGEBA) cured resins. Furthermore, final cured resin T g 's (111−151 °C) and high-temperature rubbery moduli (15−46 MPa) were easily tuned by manipulating the relative number of methoxy moieties and the regioisomer content, demonstrating the versatility and robustness of these bioinspired materials.

“…Glycidylation or epoxidation of lignin by epichlorohydrin has been widely studied to utilize glycidylated lignin as a versatile constituent of biobased epoxy resins. − The resulting lignin derivative can additionally react with various nucleophiles for further chemical modifications as epoxide rings are substituted with different functional groups via S N 2 type addition and insertion reactions. For example, epoxide rings of glycidylated lignins can be converted to cyclic carbonate groups by the addition of CO 2 .…”

Section: Results and Discussionmentioning

confidence: 99%

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

Kang

Lee

Park

et al. 2021

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.