Study On The Periodate Oxidation Mechanism Of Cellulose Fibers And The Application Of Oxycellulose Fibers

As a natural resource with high-molecular-weight polymer, cellulose is widely used. It has a degradability, low price, renewable ability and so on. Its studies and applications are beneficial to the sustainable development of human society. Periodate oxycellulose is one kind of cellulose derivatives. The selective oxidation reaction of cellulose by periodate possesses a great practical value for application. This reaction can be introduced by aldehyde groups, carboxyl groups, ketone groups, etc. These functional groups provide possibilities for further modification of cellulose, which is in favor of extending the application area of cellulose. But some mechanisms of this oxidation reaction have not been clear yet, especially the studies on application to the pulp and paper industry have been in researching stage, so it is necessary to have a further investigation in this area.This paper studied the selective oxidation reaction between periodate and bleached kraft softwood pulp. Firstly, the single factor analysis method was used to study the effects of reaction temperature, oxidant concentration, pH and pretreatment methods on the periodate oxycellulose including the content of aldehyde groups, the degrees of polymerization and crystallinity. The optimum conditions of the reaction were then obtained.Then, the physical properties of periodate oxycellulose fibers were measured. These properties include dry tensile strength index, rewet tensile strength index, elongation, etc. Topographical images of periodate oxycellulose fibers were observed by SEM and AFM. FTIR and a fiber quality analyzer were also used to analyze the quality of cellulose fibers. Finally, further modifications of oxycellulose by a grafting reaction with sodium bisulfite and chitosan were made, respectively. The modified cellulose fibers with water absorbency and an antibacterial ability were prepared, and their characteristics were investigated. Both dry and rewet tensile indices of the test sheets made of sulfonated fibers that were oxidized for 240 min before sulfonation can increase within oxidant charge of 30-50 wt %. At 50 wt % oxidant charge and 240 min oxidation duration time, the dry and rewet tensile indices of the test sheets made of sulfonated fibers could reach 62.94 N·m/g and 8.30 N·m/g, respectively. They were 506% and 67% of control sample's dry tensile index respectively. Compared with the dry and rewet tensile indices of DAC sample, the two indices of sulfonated fibers had an increase of 10% and 40%, respectively. Also the water absorbency of sulfonated fibers had been greatly increased. The periodate oxycellulose fibers grafted with chitosan had a good antibacterial ability against E. coli and 5. aureus. The reduction percentages for E. coli and S. aureus were 90.2% and 95.1%, respectively. Some topographical changes of the functional fibers were observed by using SEM and AFM. These advanced techniques can provide convenience and guarantee to characterize and analyze cellulose fibers.In a word, the periodate oxycellulose has active aldehyde groups and good physical properties, which benefites to further modification in order to get more functional materials.