Lignin as a Key Component in Lignin-Containing Cellulose Nanofibrils for Enhancing the Performance of Polymeric Diphenylmethane Diisocyanate Wood Adhesives

Abstract

Lignin-containing cellulose nanofibrils (LCNFs), an emerging family of naturebased nanomaterials, have been successfully applied in many commercial polymer systems to enhance their properties and functional performance. In particular, LCNFs were used in polymeric diphenylmethane diisocyanate (pMDI) wood adhesives as a functional compound to significantly reinforce bonding properties. In order to elucidate the mechanisms for the interactions between lignin in LCNFs and pMDI wood adhesive, 13 C− 1 H HSQC 2D-NMR experiments were carried out on dissolved ball-milled LCNFs to reveal the molecular−structural characteristics of lignin and polysaccharides in LCNFs and identify hydroxyl groups contained in these biomolecules that can be involved in reactions with the pMDI model compound. Moreover, a lignin-free CNF was prepared by chlorite treatment as a control group to illustrate the role of the lignin component in affecting the resulting adhesives. It was found that lignin was the integral component in LCNFs that is responsible for the increased reactivity as shown by curing kinetics, the improved thermal stability as shown by TGA, and the higher compatibility with nonpolar reagents as shown by lapshear tests. The fundamental knowledge gained from this study allowed us to better understand the function of the lignin component as a distinctive feature of LCNFs, and insights into the role of lignin in improving pMDI wood adhesive performance would be highly beneficial for applying LCNFs as a novel sustainable nano-bio-reinforcing agent for a wider range of polymeric systems.

Eco-Friendly High-Strength Composites Based on Hot-Pressed Lignocellulose Microfibrils or Fibers

“…In the present study, unbleached wood pulp fibers are prepared under different processing conditions so that the fibers of 40 or enzymatic hydrolysis 36 has also been used. Lignin-containing fibrils have been dispersed in the organic solvent 37 and used in adhesives, 38 Pickering emulsions, 9,39 as well as composites. 40,41 Figure 1 summarizes the preparation steps of materials based on these wood fibers and fibrils.…”

“…Based on those fibers, MFLC are prepared by mechanical fibrillation, although oxidation or enzymatic hydrolysis has also been used. Lignin-containing fibrils have been dispersed in the organic solvent and used in adhesives, Pickering emulsions, , as well as composites. , Figure summarizes the preparation steps of materials based on these wood fibers and fibrils. The materials were termed according to the process type, followed by the Kappa number (related to the lignin content).…”

Nanocellulose in Heterogeneous Water-Based Polymerization for Wood Adhesives

“…Most of the research done in this area has utilized the physical method for mixing CNPs and isocyanate adhesives. Chen et al [96] studied the addition of lignin-containing cellulose nanofibrils (LCNFs) to pMDI with promising results for wood adhesives. They showed evidence of covalent interactions between LCNFs and pMDI due to the reaction of hydroxyl groups in lignin (at the γ position) and isocyanate.…”

Efficient pretreatment using dimethyl isosorbide as a biobased solvent for potential complete biomass valorization

“…For HSQC analysis, 30 mg of lignin was dissolved in 500 µL of deuterated dimethyl sulfoxide, and the standard pulse sequence "hsqcetgpsisp.2" was used. 24 For 31 P NMR analysis, 25 mg of lignin was dissolved in a pyridine/CDCl3 (1.5/1.0, v/v, 500 µL) solution and derivatized with 75 µL 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane.…”