TEMPO-oxidized cellulose fibers from wheat straw: Effect of ultrasonic pretreatment and concentration on structure and rheological properties of suspensions.

Cellulose and TEMPO-oxidized cellulose fibers (TOCF) from the wheat straw were prepared with ultrasonic and chemical treatments to investigate structure and functionalities. Sol-gel transition of TOCF suspensions has been investigated using rheology to unveil the roles of ultrasonic pretreatment and temperature at various concentration. It was found that TOCF extracted with or without ultrasonic pretreatment exhibit similar functional groups in FTIR. However, different crystal structures and thermal stabilities were revealed in XRD and TGA, respectively. The gelation was independent of the ultrasonic pretreatment, while the rheological properties were highly infuenced by the concentration and temperature of the TOCF suspensions. TOCF suspensions presented a strain thinning behavior in large amplitude oscillatory shear tests. Lissajous curves showed that the elastoplastic behavior was predominantly modulated by the fiber concentration and strain amplitude other than the ultrasonic pretreatment. These results could improve the understanding of the relationships between TOCF structure and rheological properties.