Study On The Decrystallization Of Cellulose

Cellulose is the most abundant natural macromolecular material on the earth. With theincreasing shortage of oil resource, cellulose as a renewable resource is paid more and moreattention. However, cellulose has complex supramolecular structure with coexistence ofcrystalline and noncrystalline regions. Lots of strong hydrogen bonds exsit in the intramolecularand intermolecular of cellulose. Both of these properties determine degradation of solubility andreactivity, and it hinders the effective utilization of cellulose in industry. Therefore, this paperaims to study how to carry out decrystallization of cellulose to destroy hydrogen bonds incrystalline region, thereby obtaining low crystallinity and even amorphous cellulose and laying afoundation for efficient utilization of cellulose resources.Wood pulp cellulose was pretreated by9%NaOH with different temperature for1h. Theresult shows that at low temperature NaOH solution has stronger dissolving ability to cellulose.The temperature is lower; the ability of swelling and dissolving low DP cellulose is stronger andcellulose II gets larger percentage, besides the decrystallization is more notable. Moreover,dissolved cellulose in NaOH solution at0℃is regenerated. The configuration of regeneratedcellulose which has low crystallinity transforms to cellulose II, but its thermostability is relativelypoor than raw material.Physical and chemical interfering methods are used to make decrystallization of cellulosetreated by NaOH solution firstly. The study reveals that the best drying temperature140℃andoptimum microwave power400W are found. The crystallinity of cellulose is decreased thoughabove steps. Cellulose is freezed to-20℃and then heated to140℃suddenly, after thistreatment, the crystallinity of cellulose changes from76.3%to49.3%. Meanwhile, somechemical methods can also interfere with the recrystallization of cellulose. These chemicalmethods include changing exhalation liquid and applying three different alcohols to replace watermolecule among cellulse. As for the reasons, it's concerned with volume effect of alcohols.A composite solvent7.5wt%NaOH/11wt%urea aqueous solution is exploited to swell anddissolve cellulose when the solvent is precooled to-12℃. The swelled effection used bycomposite solvent is better than single NaOH solution. The surface area of cellulose swelled bythe composite solvent expands obviously. Similarly, physical and chemical interfering methodsare employed to make decrystallization of cellulose treated by NaOH/urea solution firstly. Itfounds that the extent of decrystallization decreases noticeably which used ethanol as exhalationliquid, and the crystallinity of cellulose changes from76.3%to57.5%。The raw material and two celluloses which through decrystallizing are all acetylized. Afteranalyzing properties of these three CA, results show that the accessibility of decrystallizedcelloluses are higher than raw material, their acetylized reaction are more fully.