Aqueous Processing of Biobased Polyamide 11/Lignin Blends with Light Color

Adding lignin into biobased polymer materials not only reduces cost but also endows multiple functions to the materials. However, the harsh conditions brought by conventional melt-blending always lead to degradation and condensation of lignin, which result in poor properties of the blends. Herein, a green and facile method called aqueous processing was used to prepare biobased polyamide 11 (PA11)/lignin blends. The conditions of aqueous processing were determined by high pressure differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). Results show that the temperature for aqueous processing is 170 °C, which is 70 °C lower than the temperature of conventional melt-blending. A model study of structural changes of lignin before and after melt-blending and aqueous processing shows that aqueous processing is beneficial to the structure stability of lignin, while melt-blending leads to severe degradation of lignin. Inspired by the advantages from aqueous processing, PA11/lignin blends with light color were achieved from aqueous processing, while melt-blending can result only in a dark brown color of the blends due to the degradation of lignin.