Effects of CELF Pretreatment Severity on Lignin Structure and the Lignin-Based Polyurethane Properties

Abstract

The impact of pretreatment severity on the structure of CELF lignin and tensile properties of CELF lignin-based PU.

Production of polyurethane elastomer from highly reactive acetic acid lignin‐derived polyols with reduced molecular weights

“…According to the E a , cross‐linking reactivities to the HDI could be related to both the molecular weight and the content of active hydroxyl groups per mass unit, with an order of HDAAL L > DAAL L > AAL (Table 6). According to the literature and the results of the study, it was confirmed that the reactivity of the lignin substitute in the synthesis of LPUE was closely related to the molecular weight and structure features 44,45 . Lignin with high molecular weight usually had a complex molecular structure and strong intermolecular hydrogen bonding, which seriously limited the lignin dispersion in the LPUE.…”

Polyurethanes Based on Unmodified and Refined Technical Lignins: Correlation between Molecular Structure and Material Properties

“…The preparation of CELF lignin was described in a previous study . In brief, the milled poplar biomass (7.5 wt % solids loading) was treated in THF/water (1:1 w/w) solution containing 0.5 wt % sulfuric acid in a 1 L Hastelloy Parr autoclave reactor (Parr Instruments Co., Moline, IL).…”

“…The polycondensation reaction between polyols and PMDI was catalyzed by 1.5% DTDL in THF . The CELF lignin samples (MCL, LCL, and CL180) and the selected hydroxyl providers such as c BED, BD, OD, PEG400, and PEG4k were employed for fabricating CL-PUs according to the formulations listed in Table .…”

“…Novel organosolv or co-solvent pretreatments developed for lignocellulosic biorefining enables lignin extraction using biomass-derived organic solvents under acidic conditions at elevated temperatures. − The co-solvent enhanced lignocellulosic fractionation (CELF) process employing miscible solutions of tetrahydrofuran (THF) and water with dilute acid can produce technical lignins featuring high lignin yield from biomass and purity. In the previous study, we have demonstrated that CELF lignin’s molecular weight, backbone structure, functional groups, and solubility in common organic solvents can be tuned by changing the pretreatment reaction conditions . We found that the mechanical performance of CELF-based PUs was determined by the solubility of CELF lignin streams in a casting solvent such as THF.…”

Acid Hydrotropic Fractionation of Lignocelluloses for Sustainable Biorefinery: Advantages, Opportunities, and Research Needs

“…Recent progress in developing fractionation processes included finding novel and better solvent systems, such as organic co‐solvent systems using γ‐valerolactone (GVL) [24] and tetrahydrofuran (THF), [25] ionic liquid (IL), [26–29] and deep eutectic solvent (DES) systems [30,31] . Although these systems are effective in efficiently solubilizing lignin and/or hemicelluloses to obtain highly digestible cellulosic fraction for enzymatic sugar production, the resultant lignin from most of these solvent systems was condensed except when fractionation was conducted under mild conditions, which decreased the enzymatic digestibility of the fractionated solids [21,32–35] . Moreover, the significantly higher costs of GVL, IL, and THF compared with conventional alkali and mineral acids, along with the higher dosages (concentrations) needed for these solvents to be effective, require a very high chemical recovery efficiency that is too difficult to achieve for economical biorefinery operations.…”