Hydrophobic, UV resistant and dielectric polyurethane-nanolignin composites with good reprocessability
Guochuang Qi, Weijun Yang, Débora Puglia, Haigang Wang, Pengwu Xu, Weifu Dong, Ting Zheng, Piming Ma
Abstract
Lignin nanoparticles (LNP) were obtained by an acidolysis process from corn pristine lignin. X-ray photoelectron spectroscopy (XPS) and radical scavenging activity (RSA) of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) confirmed a significant enhancement in reactivity of LNP in comparison with pristine lignin. Polyurethane (PU) nanocomposites were prepared by pre-polymerization of polyethylene glycol and diisocyanates in the presence of different contents (1, 3, 5 and 7 wt%) of LNP. The effects of LNP, serving as both biobased polyol and crosslinker, on the mechanical, hydrophobicity and dielectric behavior of the resulted PU nanocomposites were investigated. Tensile test results showed an overall enhancement for mechanical performance, and the elongation at break exceeded 1000% for all studied PU nanocomposites. Meanwhile, dynamic mechanical analysis (DMA) revealed that the crosslinking densities gradually increased with LNP addition. Furthermore, LNP based PU nanocomposites showed inherent resistance towards ultraviolet radiation and frequency dependent behavior for electrical conductivity. On the other hand, LNP based PU nanocomposites revealed good thermal reprocessability due to the transcarbamoylation reaction in the presence of DBTDL catalyst.