3D printing of lignin: Challenges, opportunities and roads onward

Abstract

As the second most abundant biopolymer on earth, and as a resource recently becoming more available in separated and purified form on an industrial scale due to the development of new isolation technologies, lignin has a key role to play in transitioning our material industry towards sustainability. Additive manufacturing (AM), the most efficient‐material processing technology to date, has likewise made great strides to promote sustainable industrial solutions to our needs in engineered products. Bringing lignin research to AM has prompted the emergence of the nascent “lignin 3D printing” field. This review presents the recent state of art of this promising field and highlights its challenges and opportunities. Following a review of the industrial availability, molecular attributes, and associated properties of technical lignins, we review R&D efforts at implementing lignin systems in extrusion‐based and stereolithography (SLA) printing technologies. Doing so underlines the adage of lignin research that “all lignins are not created equal,” and stresses the opportunity nested in this chemical diversity created mostly by differences in isolation conditions to molecularly select and tune the attributes of technical lignin systems towards desirable properties, be it by modification or polymer blending. Considering the AM design process in its entirety, we finally propose onward routes to bring the full potential to this emerging field. We hope that this review can help promote the unique value and overdue industrial role of lignin in sustainable engineered materials and products.

Understanding the Coupling Effect between Lignin and Polybutadiene Elastomer

“…On the other hand, lignin was utilized to develop shape memory polymer [8], self-healing elastomer [9], and renewable skin with programmable and switchable electrical conductivity [10]. Furthermore, lignin was used in energy storage [11] and 3D printing applications [12]. Lignin was also used as a precursor to produce high-performance carbon fibers [13].…”

Use of Wood in Additive Manufacturing: Review and Future Prospects

“…Depending on biomass source and processing routes, different strains of lignin are produced, such as alkaline lignin, kraft lignin, organosolv lignin and others [ 16 ]. The inherent properties of lignin (i.e., antioxidant and antibacterial properties) but also its tendency to revert to humus after biodegradation can be expected to be preserved in lignin-based parts [ 36 ].…”

An Overview of Natural Polymers as Reinforcing Agents for 3D Printing

“…Chemically, it is a hetero-polymer derived from the cross-linking of three different substituted phenols (lignols): coniferyl, sinapyl, and p-coumaryl alcohols. From wood pulping, three types of industrial lignin can be obtained, such as kraft lignin, oganosolv lignin and lignosulfonate, which are materials exploited for different applications, including 3D printing [44]. The interest in lignin has been growing in recent years since its availability has been markedly increased as a consequence of the development of more efficient processes for isolation and purification on an industrial scale.…”