The Effects Of Enzyme Treatment And Chemical Method On The Preparation Technology And Property Of Wheat Micro/nano Fibrils

In this thesis, wheat straw was selected as research object to study on the optimumtechnology conditions of cellulose micro/nano fibrils separated by the method of chemicalcombined with cellulase treatment. This thesis characterized the micro/nano fibrils which wasseparated in the experiment by TEM, FTIR, XRD and DSC analysis, and then explored thetechnology of produce three-ply plywood using UF resin modified by micro/nano fibrils.Conclusions based on this thesis were shown as follows:(1) Most hemicellulose and lignin in the wheat straw was wiped off by digesting andoxidation, and isolated high purity wheat straw cellulose would be a good substrate ofenzymolysis of cellulase.The optimum digesting technology conditions: alkali dosage was12%, digesting temperature was150℃and digesting time was4hours. The optimumoxidation technology conditions: oxidation temperature was70℃, oxidation time was6hoursand hydrogen peroxide concentration was5%. After digesting and oxidation, the cellulosewhose dry content was88.32%was obtained, and it was a good substrate of enzymolysis ofcellulase.(2) The solid enzyme activity of cellulase used in this thesis was148.45FPU/g. In orderto accelerae the enzymolysis and save the enzyme dosage, the added enzyme dosage wasselected as35FPU/g. When the added enzyme dosage was less than35FPU/g, enzymolysiseffect of cellulase would improve observably with the increase of dosage. But when the addedenzyme dosage was more than35FPU/g, enzymolysis effect of cellulase would not improveobservably with the increase of dosage. In the condition of35FPU/g enzyme dosage,enzymolysis efficiency would decrease with the enzymolysis time prolongation, the studyshowed that the optimum enzymolysis time was48hours. By separating the enzymolysisproduct and ultrasonic dispersing treatment, Micro/nano fibrils would be prepared. Themicro/nano fibrils would aggregate in the water, and the mean diameter of micro/nano fibrilsaggregate is31.192micrometer.(3) TEM analysis showed that the length of a single fibril is between100-300nm and thediameter of a single fibril is between10-20nm, met the requirement of micro/nano fibrils.FTIR analysis illustrated the dominated component of micro/nano fibrils generated byenzymolysis was cellulose. According to XRD analysis, enzyme treatment could improve thecrystallinity of wheat micro/nano fibrils, and the crystallinity would decrease if the ultrasonictime was excessive. DSC analysis showed that thermal property of cellulose had not changedobviously after enzyme treatment and ultrasonic treatment, its thermal stability was very good when the temperature under300degree centigrade.(4) Adding3%micro/nano fibrils was beneficial to UF curing in only one time and itcould decrease the curing temperature in some extend. When hot-press temperature was within105-135degree centigrade, the effect of added amount of micro/nano fibrils on the bondingproperty was significant. The result manifested that the bond strength of the modify UF resinwould be the best in the test interval when the added amount of micro/nano fibrils was3%.