Formulation of Multifunctional Materials Based on the Reaction of Glyoxalated Lignins and a Nanoclay/Nanosilicate

Abstract

Two organosolv lignins from different origins, namely, almond shells and maritime pine, were modified by using a nanoclay and nanosilicate. Prior to modification, they were activated via glyoxalation to enhance the reactivity of the lignins and thus ease the introduction of the nanoparticles into their structure. The lignins were characterized by several techniques (Fourier transformed infrared, high-performance size exclusion chromatography, 1H NMR, X-ray diffraction, and thermogravimetric analysis) before and after modification to elucidate the main chemical and structural changes. The reaction with glyoxal proved to increase the amount of hydroxyl groups and methylene bridges. This tendency was more pronounced, as the percentage of glyoxal was incremented. On the other side, the addition of the nanoclay and nanosilicate particles improved the thermal stability of the lignins compared to that of the original unmodified ones. This trend was more evident for the lignin derived from maritime pine, which displayed better results regarding the thermal stability, indicating a more effective combination of the nanoparticles in the lignin structure during the modification process.

Wood Fireproofing Coatings Based on Biobased Phenolic Resins

“…The previous degradation stages occurred at temperatures similar to those reported in a previous work for the functionalized lignins alone . Nevertheless, in this case of cured resins, the percentage of weight loss associated with each stage was considerably reduced compared with that of the modified lignins alone (Appendix C2 of the Supporting Information).…”

“…The previous degradation stages occurred at temperatures similar to those reported in a previous work for the functionalized lignins alone. 48 Nevertheless, in this case of cured resins, the percentage of weight loss associated with each stage was considerably reduced compared with that of the modified lignins alone (Appendix C2 of the Supporting Information). This corroborates the presence of a polymeric structure of greater thermal resistance than that of its constituents alone, which would have been developed during the previous curing of the resins.…”

“…The mentioned process of functionalization has already been comprehensively described in a previous work. 48 On the other hand, a tannin solution was prepared based on commercial mimosa extracts, which displayed a Stiasny number of 89.46 ± 2.46. 49 The solution was performed by dissolving the commercial mimosa extract in acetone (30%) at a concentration of 45% (w/w).…”

“…The reaction was left overnight until complete dissolution of the nanoparticles. The mentioned process of functionalization has already been comprehensively described in a previous work . On the other hand, a tannin solution was prepared based on commercial mimosa extracts, which displayed a Stiasny number of 89.46 ± 2.46 .…”

Biobased Resins Using Lignin and Glyoxal

“…For instance, de Hoyos-Martínez et al and El Mansouri et al applied G/L molar ratios of, respectively, 0.25–0.58 and 2 (Table ). , Throughout their work, it is not specified how the molarity of lignin is defined, and therefore, this molar ratio cannot be converted to a mass ratio of glyoxal solution to lignin. Furthermore, a solid content between 30% and 40% is regularly reported for these solutions.…”