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.
Valorisation of waste to yield recyclable composites of elemental sulfur and lignin
Lignin is the second-most abundant biopolymer in nature and remains a severely underutilized waste product of agriculture and paper production. Sulfur is the most underutilized byproduct of petroleum and natural gas processing industries. On their own, both sulfur and lignin exhibit very poor mechanical properties. In the current work, a strategy for preparing more durable composites of sulfur and lignin, LSx , is described. Composites LSx were prepared by reaction of allyl lignin with elemental sulfur, whereby some of the sulfur forms polysulfide crosslinks with lignin to yield a three-dimensional network. Even relatively small quantities (<5 wt%) of the polysulfide-crosslinked lignin network provides up to a 3.4-fold increase in mechanical reinforcement over sulfur alone, as measured by the storage moduli and flexural strength determined from dynamic mechanical analysis (temperature dependence and stress–strain analysis). Notably, LSx composites could be repeatedly remelted and recast after pulverization without loss of mechanical strength. These initial studies suggest potential practical applications of lignin and sulfur waste streams in the ongoing quest towards more sustainable, recyclable structural materials.
- Award ID(s):
- 1708844
- Publication Date:
- NSF-PAR ID:
- 10097959
- Journal Name:
- Journal of Materials Chemistry A
- ISSN:
- 2050-7488
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1039/C9TA03222C
