Improving aging resistance and mechanical properties of waterborne polyurethanes modified by lignin amines

In this article, we report the enhanced anti-aging and mechanical properties of waterborne polyurethanes (WPUs) modified by lignin amines, which were prepared from lignins, formaldehyde, and diethylenetriamine via a Mannich reaction. When we introduced amino groups into the lignin, its solubility in water and reactivity with isocyanate was obviously improved. Consequently, the interaction between WPU and the lignin additive were promoted; this provided a higher mechanical performance, that is, a higher tensile strength and elongation at break. More importantly, the intrinsic antioxidative activity of lignin also benefitted the modified WPU in terms of aging resistance. According to artificial accelerated aging tests, mechanical measurement, attenuated total reflectance-Fourier transform infrared spectroscopy, and scanning electron microscopy analysis, the lignin amine modified WPU did not show any evidence of degradation after 2 months of artificial accelerated aging, whereas the pure WPU was obviously degraded. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1736-1742, 2013