Fig. 4From: Green construction and release mechanism of lignin-based double-layer coated ureaTGA weight loss curves of the LPUs with different lignin content and EP (a1), and different -CNO/-OH molar ratio (a2). WCA of the LPUs with different lignin content and LPU-EP (b1), and different -CNO/-OH molar ratio (b2). The degradation ratio of the coating layer in soil (c1). SEM images of the 0 (c2) and after 180 days (c3) coating layer of the LDCU in the soilBack to article page