Reacting Cotton Cellulose with Lignin-Based Polyurethane

Abstract

Chain-extended lignin was reacted with blocked isocyanate and the product, lignin polyurethane (LPU), was subsequently applied by padding to cotton print cloth at three add-on levels: 1.70, 3.45, and 4.30%. Product syntheses and reactivity were followed by FTIR spectroscopy. LPU as a formaldehyde-free finish improved durable press (DP) and dimensional stability of the unfinished cloth, but the improvement was less than conventional amino resin finishes. Unlike conventional resin finishes, LPU showed strength and abrasion resistance retention. Abrasion resistance improved at the 3.5% add-on level. Grafting LPU onto cotton cloth is a surface reaction, given the molecular size of the product and detection by specular reflectance infrared spectroscopy. Even with the limited accessibility of the reactant groups in the unswollen cloth, a sufficient number of carbamoyl linkages formed to improve properties. Although DP ratings were not high, LPUs tailored by alkyloxyhydroxide chain extensions are likely resins for films, nonwoven consolidants, and composite materials, providing receptivity of cellulose to materials for which it has little affinity.