The Effect of Plant Source on the Properties of Lignin-Based Polyurethanes

Abstract

This work increases our understanding of the effect of plant source on the mechanical and morphological properties of lignin-based polyurethanes (PUs). Lignin is a polymer that is synthesized inside the plant cell wall and can be used as a polyol to synthesize PUs. The specific aromatic structure of the lignin is heavily reliant on the plant source from which it is extracted. These results show that the mechanical properties of ligninbased PUs differ based on lignin's plant source. The morphology of lignin-based PUs was examined using atomic force microscopy and scanning electron microscopy and the mechanical properties of lignin-based PU samples were measured using dynamic mechanical analysis and shore hardness (Type A). The thermal analysis and morphology studies demonstrate that all PUs prepared form a multiphase morphology. In these PUs, better mixing was observed in the wheat straw lignin PU samples leading to higher moduli than in the hardwood lignin and softwood lignin PUs whose morphology was dominated by larger aggregates. Independent of the type of the lignin used, increasing the fraction of lignin increased the rigidity of PU. Among the different types of lignin studied, PU with wheat straw soda lignin exhibited storage moduli ~2-fold higher than those of PUs incorporating other lignins. This study also showed that during synthesis all hydroxyl groups in the lignin are not available to react with isocyanates, which alters the number of cross-links formed within the PU and impacts the mechanical properties of the material.

Lignin-Derived Biomaterials for Drug Release and Tissue Engineering

“…Scaffolds seeded with hBMSCs showed improved osteogenesis compared to conventional PU scaffolds [ 104 ]. Since lignin-based polyurethanes are already available in various compositions with tunable mechanical stability and degradability, lignin-PU in future will become favored candidates to be studied in detail regarding their ability to be used for both, biodegradable tissue engineering scaffolds and drug encapsulation materials [ 105 , 106 ].…”

Unmodified kraft lignin isolated at room temperature from aqueous solution for preparation of highly flexible transparent polyurethane coatings

“…Most probably, deprotonated phenolates catalyze isocyanate reaction (with other isocyanates and/or urethanes) resulting in trimer and allophanate signals. 51,52 During process optimization, the NCO residuals could further be reduced to a very weak signal (Fig. 16).…”

Miscanthus x giganteus Stem versus Leaf-derived Lignins Differing in Monolignol Ratio and Linkage

“…Currently, there are approximately 17 species investigated in Europe for energy and material development including Miscanthus tinctorius, M. sinensis, M. sacchariflorus and the triploid genotype M. x giganteus, an allotriploid hybrid of the diploid M. sinensis and the tetraploid M. sacchariflorus. Miscanthus field trials have been performed in Europe over the past 25 years and their linkages differ significantly [49][50][51][52][53][54][55][56][57][58][59][60]. Figure 1 shows the most common linkages of lignin formed during biosynthesis, some of them confirmed within the last five years [55,61,62].…”