Study On The Dissolution Of Cellulose In Phosphoric/Polyphosphoric Acid System

Cellulose is a most redundant natural polymer material on earth. With the increasing shortage of oil resources, people pay more attention to cellulose. One of the most important purposes of cellulose is used in the manufacture of fiber. There are many processing methods to produce cellulose fiber such as the viscose and NMMO process. The viscose process has serious environmental problem. The NMMO process cost very high. In this paper, the phosphoric/ polyphosphoric acid blends are used as solvent, the dissolving and liquid crystalline behavior of cellulose in the blends are studied.In this thesis the optimum process is gained by varying concentration of P2O5, cellulose concentration and temperature, which is 74wt. % of P2O5-concentration, 15wt. % of cellulose- concentration at 30℃.Cellulose was pretreated respectively with ultrasonic, NaOH-solution and CaCl2-solution. The changes of structure and properties of different solution were investigated by XRD, IR and SEM. It can be concluded that pretreatments contribute much to the enhancement of the accessibility and reactivity of cellulose.The formation mechanism of a band texture of cellulose in phosphoric/polyphosphoric acid has been investigated by using parallel shear and rotating shear. A model was suggested to describe the formation mechanism of band texture for liquid crystalline state of cellulose in phosphoric/polyphosphoric acid by shear.DP of the cellulose was determined with copper ethylenediamine in the dissolution process at different times. The changes of structure and properties were investigated by XRD and IR. The mechanism of degradation in phosphoric/polyphosphoric acid was explored. The results showed that DP of the cellulose decreased greatly. XRD showed that crystal style of the cellulose changed from celluloseⅠinto celluloseⅡ. No new peak found in infrared spectra showed that no cellulose derivatives formed.