Recovery of the Structure, Characteristics, and Application of Thermal Drying-Deteriorated Cellulose Fibers

Abstract

The large-scale and multilevel application of renewable cellulose resources is one of important strategies for the sustainable development of human society. However, thermal drying is usually an inevitable procedure during utilization of cellulose fibers and it leads to hornification of cellulose fibers, which seriously hinders their further development. A typical feature of hornification is the irreversible shrinkage of cellulose fibers, including shrinkage of the cell lumen, cell wall, and pores on it. These macroscopic structural changes originate from the recrystallization of cellulose molecules caused by forced dehydration during processing. Here, an easy NaOH-urea treatment method to reverse the hornification of hornified cellulose fibers (HCFs) was proposed. The cell lumen, cell wall, and pores of HCFs were restored, and the hydroxyl groups were released inside and on the surface of the fibers; the water retention value (WRV) was relatively increased by 41.8%, and the hornification was reversed by 79%. The drying-induced crystallization and cocrystallization of amorphous cellulose were disrupted, which proved that NaOH-urea treatment can realize a procedural hornification reversal. Finally, the promotion of NaOH-urea treatment on the application of HCFs was verified and explained. This paper will make an important contribution to the reversible characteristic regulation, multiple utilization, efficient recycling, and reuse of cellulose materials.