Fig. 3From: Green construction and release mechanism of lignin-based double-layer coated ureaFT-IR analysis of the AL, PCLD, HDI, E44, EP (a1), and the LPUs obtained under the different conditions (a2: lignin content; a3: -CNO/-OH molar ratio). 13C NMR spectra of AL (b1), PCLD (b2), HDI (b3) and the LPU (b4)Back to article page