The use of lignin as cross-linker for polyurethane foam for potential application in adsorbing materials

Abstract

Lignin was extracted from wheat straw and used for its crosslinking function in the synthesis of polyurethane foam (PUF). The effects of lignin’s addition on the cross-linking structure and macroscopic properties of the PUFs were investigated. A morphological examination, Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA) were conducted to measure the performance of the polyurethanes. Kinetic models were simulated to analyze the oily solvent adsorption mechanism of the polyurethane. The results showed that an increase in the cross-linking density was conducive to an improvement of the physical properties of the polyurethane. Moreover, the process of oily solvent adsorption was in accordance with the quasi-second-order kinetic model. Both physical and chemical adsorption occurred during the adsorption process. This work demonstrated a highly effective method for imparting PUFs with an excellent performance and proper lignin content.

Antibacterial Polyurethane Foams with Incorporated Lignin-Capped Silver Nanoparticles for Chronic Wound Treatment

“…In particular, according to one-way ANOVA results, a significant difference in the cell size was found between PUF-0 and PUF-0.25%NP, having the highest AgPL NPs content ( F (3, 398) = 12.87; p < 0.0001). A similar tendency was observed in previous works, where increasing the concentration of lignin and nanoparticles reduced the size of PUF cells. A decrease of the cell size may be explained by cross-linking of the PUF structure due to (i) involvement of the lignin shell of the AgPL NPs in polymerization with the isocyanate component and (ii) coordination of the polyurethane chains by H-bonds with the lignin-capped NPs .…”

“…Chung and co-workers reported an increase in the cross-linking density of lignin-based polyurethane prepared with chemically modified lignin, which was attributed to better integration of the modified lignin, containing a higher concentration of hydroxyl groups, into the covalent polymer network . In this work, the hydroxyl groups of lignin present in the AgPL NPs may have reacted with isocyanate to generate urethane bonds involving the lignin shell of the NPs, thus increasing the cross-linking density of the foams. ,,, Customization of the swelling profiles of these PUFs by modulating their AgPL NPs content would allow for their use as absorbing materials for moderately to highly exudating wounds.…”

“…The incorporation of AgPL NPs in the foams led to lower swelling ratios, suggesting an increase of PUFs’ cross-linking density. , The swelling index decreases from 1145% to 585% when the concentration of AgPL NPs rises from 0.12 to 0.25%. Li et al (2017) found a correlation between the lignin content and the cross-linking densities of PUFs when the content of lignin was raised from 0 to 1% . Chung and co-workers reported an increase in the cross-linking density of lignin-based polyurethane prepared with chemically modified lignin, which was attributed to better integration of the modified lignin, containing a higher concentration of hydroxyl groups, into the covalent polymer network .…”

“…The lignin matrix embedded with Ag NPs has possibly reacted with isocyanate to integrate into urethane bonds in the polymer structure. Such a covalent interaction, in addition to formation of hydrogen bonds between the lignin shell of the nanoparticles and the polyurethane macromolecules, would prevent the burst release of silver. ,, Additionally, the different slopes observed in Figure indicate that Ag release behavior depends on the AgPL NPs content in the PUFs. Increasing the content of AgPL NPs resulted in a slower Ag release, probably due to a higher density of the polyurethane matrix caused by a higher cross-linking of lignin in the PUF structure, which hindered the release of Ag + from the NPs.…”

“…The incorporation of AgPL NPs in the foams led to lower swelling ratios, suggesting an increase of PUFs' cross-linking density. 32,38 The swelling index decreases from 1145% to 585% when the concentration of AgPL NPs rises from 0.12 to 0.25%. Li et al (2017) found a correlation between the lignin content and the cross-linking densities of PUFs when the content of lignin was raised from 0 to 1%.…”