Abstract
Lignin is the most abundant aromatic biopolymer and is the sustainable feedstock most likely to supplant petroleum-derived aromatics and downstream products. Rich in functional groups, lignin is largely peerless in its potential for chemical modification towards attaining target properties. Lignin’s crosslinked network structure can be exploited in composites to endow them with remarkable strength, as exemplified in timber and other structural elements of plants. Yet lignin may also be depolymerized, modified, or blended with other polymers. This review focuses on substituting petrochemicals with lignin derivatives, with a particular focus on applications more significant in terms of potential commercialization volume, including polyurethane, phenol-formaldehyde resins, lignin-based carbon fibers, and emergent melt-processable waste-derived materials. This review will illuminate advances from the last eight years in the prospective utilization of such lignin-derived products in a range of application such as adhesives, plastics, automotive components, construction materials, and composites. Particular technical issues associated with lignin processing and emerging alternatives for future developments are discussed.
Highlights
The word “lignin” is derived from the Latin word “lignum”, meaning “wood” [1]
Radical-induced aryl halide/sulfur polymerization (RASP) proved effective for preparation of high sulfur-content materials (HSMs) but employing aryl halides in place of the olefins required for inverse vulcanization
The sulfur and chlorolignin are fully miscible at the 240 ◦ C reaction temperature, allowing them to be reacted in any ratio
Summary
The word “lignin” is derived from the Latin word “lignum”, meaning “wood” [1]. It is in wood that lignin may be most familiar to the layperson. Lignin is comprised of a isocyanate high number of exhibit moderate selectively for reaction with aliphatic OH groups over phenolic groups. Due to the prevalence of bulky fragments in lignin, isocyanate groups do not react with all of the OH groups of lignin For these reasons, the greatest success has been observed when the NCO/OH ratio is high, generally ≥1.0 mol NCO/mol hydroxyl [11]. The greatest success has been observed when the NCO/OH ratio is high, generally ≥1.0 mol NCO/mol hydroxyl [11] Another strategy to increase coupling to lignin particles is to modify lignin to increase its solubility and to increase the number of aliphatic OH groups available for reaction. Modulus 3.41 Mpa lignin facilitate discussion, products are classified as modified and unmodified lignin-based polyurethanes
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