# Lignin to Materials: A Focused Review on Recent Novel Lignin Applications
## 5 3D Printing Lignin-Plastic Composites  
Blending lignin with various plastic materials to form 3D printing composites has recently received attention. The ideal 3D printing material has excellent extrudability to ease the process of 3D printing while also being strong so that the final printed material can retain its structure. Lignin has several structures that are advantageous for 3D printing: aliphatic ether groups, \(\beta\)-O-4' linkages, and oxygenated aromatic bonds [49; 50]. Incorporating lignin into plastic materials traditionally used for 3D printing results in composites that can be used for a more environmentally friendly and cost-effective 3D printing process. There has also been recent discussion with energy sacrificial bonds as a mechanism for strong biomaterials, including lignin. Such sacrificial bonds dissipate energy through rupturing and reform by stretching. In light of this, a study investigated Zn-based coordination bonds between lignin nanoparticles and an elastomer matrix [51]. Such bonds were found to facilitate the dispersion of lignin in the matrix, thereby enhancing the strength of the composite. This study reported that a \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Product** & **Feedstock** & ** Lignin Content (wt \%)** & **Reaction/Process Condition** & **Source** \\ \hline Supercapacitor & Alkali lignin & 30–70\% & \begin{tabular}{c} Electrospinning aqueous alkali lignin and PVA, \\ temperature stabilization in the tube furnace ramped from 25 to 220 \({}^{\circ}\)C, red at 220 \({}^{\circ}\)C for 8 h. \\ Lignin, PVA, and distilled water mixed at 60 \({}^{\circ}\)C for 1 h \\ and at room temperature for 4 h, followed by \\ electrogroiming \\ Supercapacitor & Steam explosion lignin & 17–50\% \\ Lithium battery & \begin{tabular}{c} Hydolysis lignin \\ Acetone lignin from \\ corn stalks \\ \end{tabular} & 76\% & \begin{tabular}{c} Ball milled to 30 microns, washed with distilled water \\ in centrifuge for 10–12 h, dried at 60 \({}^{\circ}\)C for 24 h. \\ Stabilized at 300 \({}^{\circ}\)C for 2 h in N\({}_{2}\) in tube furnace. \\ \end{tabular} & [43] \\ Supercapacitor & Softwood alkali lignin & 75\% & \begin{tabular}{c} Thermoplastic \\ elastomeric polyurethane, dimethylformamide, PLA \\ stirred at 50 \({}^{\circ}\)C for 5 min before electrospinning. \\ \end{tabular} & [44] \\ Supercapacitor & Steam explosion lignin & 17–50\% & \begin{tabular}{c} EM, post-treatment by washing with hot water and \\ drying at 100 \({}^{\circ}\)C overnight. \\ Ball milled to 30 microns, washed with distilled water \\ in centrifuge for 10–12 h, dried at 60 \({}^{\circ}\)C for 24 h. \\ Stabilized at 300 \({}^{\circ}\)C for 2 h in N\({}_{2}\) in tube furnace. \\ \end{tabular} & [45] \\ Lithium battery & \
\begin{tabular}{c} Organoslov hardwood \\ lignin \\ \end{tabular} & 50–80\% &
\begin{tabular}{c} Stabilized at 300 \({}^{\circ}\)C for 2 h in N\({}_{2}\) in tube furnace. \\ Thermoplastic \\ elastomeric polyurethane, dimethylformamide, PLA \\ stirred at 50 \({}^{\circ}\)C for 5 min before electrospinning. \\ \end{tabular} & [46] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the studies on the electrochemical applications of lignin. Figure 5: Reaction mechanism using the pyrolysis technology. Reprinted from reference [47], with permission from Elsevier. lignin loading as high as 30 wt % can increase the strength, ductility, and toughness of thermoplastic elastomers, which can be used for 3D printing. Several studies show that lignin can enhance structural properties of 3D printing materials. Table 3 summarizes recent studies on the application of technical lignins to 3D printing materials. In a study, when Kraft lignin was blended with acrylonitrile butadiene styrene (ABS), the result was a more brittle structure; this composite demonstrated low tensile energy and strength [49].