Anthraquinone-assisted deep eutectic solvent degumming of ramie fibers: Evaluation of fiber properties and degumming performance

Deep eutectic solvent (DES) is proved to be versatile for ramie fiber isolation due to its high degumming efficiency and feasible recycling process. However, ramie cellulose is easily to be chemically degraded during the intense reaction if the treatment conditions cannot be properly controlled, affecting the mechanical properties of ramie fibers. In this paper, anthraquinone (AQ), serving as effective cellulose protection agent, was applied in the process of DES degumming to enhance the properties of treated fibers. Under the addition of 0.2 g/L AQ, there was an increase of 3.2% in the degree of polymerization and 5.56% in the crystallinity. Besides, the breaking tenacity, breaking elongation, and work of rupture of degummed fibers increased by 8.44%, 11.94%, and 33.33%, respectively. The chemical structure and thermal properties were also analyzed and compared between degummed fibers with or without cellulose protection agent. It is found that a small amount of AQ could improve the degradation temperature of fibers, accelerate the removal of lignin, and protect carbohydrates from excessive degradation. Considering these significant advantages, intrinsic greenness of DES, as well as the auxiliary effect and inexpensiveness of AQ, this new degumming method holds enormous potential for natural fiber extraction.