Article

Lignin Esters for Use in Unsaturated Thermosets: Lignin Modification and Solubility Modeling

University of Delaware, Ньюарк, Delaware, United States
Biomacromolecules (Impact Factor: 5.75). 07/2005; 6(4):1895-905. DOI: 10.1021/bm0500345
Source: PubMed

ABSTRACT

Kraft lignins from hardwood and softwood were esterified with several anhydrides to alter their solubility behavior in nonpolar solvents, such as styrene-containing thermoset resins. The esterification reaction was facile, it reduced the amount of waste products, and can be readily scaled up. Increasing the carbon chain length on the ester group improved the solubility of kraft lignin in nonpolar solvents, with butyrated lignin being completely soluble in styrene. Esterification with unsaturated groups such as methacrylic anhydride, improved the solubility to a lesser extent than the saturated analogues. The solubility behavior of the modified lignin was described using the Flory-Huggins solubility theory, combined with the predictive method of Hoy. The main goal to obtain a styrene soluble kraft lignin that could be used in unsaturated polyesters and vinyl esters was achieved with fully butyrated kraft lignin and a butyrated/methacrylated kraft lignin. The solubility of the latter is governed by the butyrate/methacrylate ratio. The reaction rate constants for the butyration and methacrylation reactions were also determined and the aromatic hydroxyl groups were found to be consistently three times more reactive than the aliphatic ones.

Download full-text

Full-text

Available from: R. P. Wool, Jul 23, 2014
  • Source
    • "Synthesis of esterified Kraft lignins (following the procedure of Thielemans and Wool 2005) Kraft lignin was esterified with succinic anhydride. A ratio 1/5 w/w of lignin/succinic anhydride was mixed with 1,4-dioxane (20 mL g 21 lignin) and 1 mL of a solution containing 0?5 g of 1-methylimidazole in 10 mL of 1,4-dioxane was added per grams of lignin to catalyse the reaction. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hardwood Kraft lignins were esterified with succinic anhydride and chemically, thermally and morphologically characterised compared to their unmodified counterparts. Esterification was confirmed by NMR and Fourier transform infrared spectrometer (FT-IR). Esterified lignins were found to be porous, less thermally stable and slightly more hydrophilic than unmodified lignins because esterification with cyclic acid anhydride is accompanied with the simultaneous liberation of carboxylic acid groups. These free carboxylic acid groups are interesting for panel production as they could create new ester groups with wood components. The wood particleboard panels were produced via compression moulding using different concentrations of unmodified and esterified Kraft lignins as sole binders (10, 20 and 30%). All the mechanical properties [impact strength, modulus of elasticity (MOE) and modulus of rupture (MOR)] of the studied wood particleboard panels significantly increased with the addition of the succinated and unmodified Kraft lignins. However, the best mechanical properties were determined for panels containing 20% of unmodified Kraft lignins. Therefore, the condensation reactions of the unmodified Kraft lignins taking place during the compression moulding seem explain why these lignins act as a more efficient binder than the succinated lignins.
    Full-text · Article · Jun 2015 · International Wood Products Journal
  • Source
    • "This process consists of extracting lignin from lignocellulosic fibre by an organic solvent with water, normally under acid catalysis; this is advantageous because it results in lignin with a low molecular weight compared to other processes . This process lends lignin a large number of reaction sites, making it a more appropriate modifying agent [24]. The goal of this work was to investigate the effects of the chemical modification of chitosan using a binary modifying agent composed of organosolv lignin and acrylic acid, on the mechanical and thermal performances of chitosan-filled polypropylene composites. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This work investigates the effects of the binary modifying agents–organosolv lignin and acrylic acid, on the mechanical and thermal properties of chitosan-filled polypropylene (PP) composites. We analyse the mechanical and the thermal properties of the composites by means of ASTM D 638-91, ASTM D 256, thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Tensile strength of the composites decreases upon the addition of chitosan, but Young’s modulus improves. Impact strength is found to increase with the maximum value at 30 php. The chemical modifications do not alter the stress–strain character or the thermal degradation mechanism of the composites considerably; however the results of this study show that the treated composites are found to have better mechanical and thermal properties than untreated composites. Furthermore, the obtained results are comparable to results from previous work. This outcome implies that organosolv lignin could be a potential reagent to partially replace its synthetic counterpart.
    Full-text · Article · Mar 2013 · Composites Part A Applied Science and Manufacturing
  • Source
    • "Recently, lignin esters have been proposed for use as unsaturated ester thermosets [178]. Following a fast and simple procedure, kraft lignins were esterified with anhydrides to render them more soluble in styrene. "
    [Show abstract] [Hide abstract]
    ABSTRACT: This review presents the recent advances in the synthesis, properties and applications of thermosetting materials derived from renewable resources. Thermosetting materials are highly cross-linked polymers that are cured or set using heat, or heat and pressure, and/or light irradiation. This leads to high-performance products for industry due to their high modulus, strength, durability and resistance towards thermal stress and chemical attacks as provided by their high cross-linking density. Within this contribution, a special emphasis was made on a broad-brush approach over the potential opportunities and drawbacks concerning the use of renewable feedstock in the design of some commonly used networks such as phenolics, epoxy, polyester and polyurethane resins. Thereby, the utilization of renewable resources is discussed as a novel and appropriate sustainable feedstock rather than as a substitute for petroleum-based thermosetting materials.
    Full-text · Article · Apr 2010 · Progress in Polymer Science
Show more