Valorization of Lignin as a Sustainable Component of Structural Materials and Composites: Advances from 2011 to 2019

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.

Robust, remeltable and remarkably simple to prepare biomass–sulfur composites

“…[1][2][3][4][5] Even once separated, the lignin is a high-volume, low-value commodity whose full potential has yet to be leveraged. 6 As part of our ongoing effort to explore the viability of lignocellulosic biomass as a precursor to durable composites, we recently reported a process by which agricultural by-product peanut shells can be converted to a composite having mechanical properties that rival those of familiar structural materials like Portland cement. 7 This process involved a low-temperature aqueous olefination of finely-ground peanut shell powder (particle size r300 mm, Fig.…”

A role for terpenoid cyclization in the atom economical polymerization of terpenoids with sulfur to yield durable composites

“…Inverse vulcanization has proven successful for producing materials from a range of petrochemical and renewably-sourced olefins, 8 including terpenoids, [11][12][13][14][15] triglycerides, [16][17][18][19][20][21][22][23] fatty acids, [24][25][26][27] sorbitan esters, 28 amino acid derivatives, 29 guaiacol derivatives, 30 and cellulose/lignin derivatives. [31][32][33][34] Many applications for resulting materials have been noted, 35,36 as highlighted in the aforementioned references. Significant advances in synthetic methodologies to allow lower-temperature/catalytic reactions [37][38][39][40] and facile processing 41,42 of high sulfur-content materials have recently made high sulfur content materials even more attractive candidates for commercialization.…”

“…The Smith group has recently explored strategies for preparing biomass-derived sulfur composites made from organic small molecules, traditional petrochemical composites, biocomposites, and amino acid-based monomers with a primary goal of developing durable structural materials. [25][26][27]29,[31][32][33][34][43][44][45] These composites have shown mechanical strength profiles that in some cases outperform commercial building materials such as glass fibre-reinforced polymer composites or Portland cement. Unfortunately, some of these sulfur composites require several steps for monomer synthesis, detracting from the atom economy, greenness, and affordability of the processes.…”

Preface to Special Issue of ChemSusChem on Lignin Valorization: From Theory to Practice

“…The lignin‐polyurethane could be further converted into competitive materials, such as films, coatings, adhesives, and rigid foams . Similarly, lignin‐based phenol‐formaldehyde (LPF) resin is also an important utilization pathway owing to the aromatic structure of the lignin polymer . Phenolation modification of lignin is usually favorable prior to preparing LPF resin because the resulting LPF resins possess desirable viscosity, low residual solids content, and low formaldehyde/phenol emission comparable to commercial PF resins in similar applications .…”

“…Similarly, lignin‐based phenol‐formaldehyde (LPF) resin is also an important utilization pathway owing to the aromatic structure of the lignin polymer . Phenolation modification of lignin is usually favorable prior to preparing LPF resin because the resulting LPF resins possess desirable viscosity, low residual solids content, and low formaldehyde/phenol emission comparable to commercial PF resins in similar applications . Benefiting from the presence of hydrophilic functional groups, lignin can be used as a formulation polymer for hydrogel preparation, and the resulting products are applicable in the areas of agriculture, environmental pollution treatment, and biomedicine, and as stimuli‐responsive materials, flexible supercapacitors, and electronics, among others .…”