| Microfibrillated cellulose (MFC) offers some unique performance due to its large surface area, biodegradability, excellent mechanical properties and the blocking performance, and has been used in various domains, such as reinforcement of nanocomposites, paper making and aerogel, etc. The chemical pretreatment methods commonly used in the current MFC preparation process limit its application areas and large-scale production to a certain extent for the potential environmentally problems. In this paper, the special advantages of Fenton (H2O2/Fe2+) oxidation system, such as green environmental protection and strong oxidization, were applied to MFC oxidation pretreatment, and its basic reaction mechanism and the application characteristics of Fenton-MFC product on improving the initial wet strength of the paper were studied.The influence of main factors such as the dosage of H2O2 and the amount of FeI2+ on the properties of cellulose were investigated. The SEM and AFM analysis showed that the MFC had a diameter of several tens to several hundred nanometers and a length of several to several tens of micrometer, there was no significant impact on the fiber morphology;FTIR, NMR and XRD were used to characterize MFC and the Fenton reaction mechanism was proposed: 1) The hydrogen bond between the cellulose molecules can be transferred to carboxyl groups by H2O2 catalyzed by ferrous iron, and the negative charge (COO-) caused the rejection of cellulose molecules; 2) HO· generated by H2O2 in the presence of Fe2+ can react with cellulose penetrated into most of disordered regions of native cellulose micro-fibrils and then caused the remarkable de-polymerization of oxidized celluloses,which establish a good condition for the fibrillation of cellulose in the follow-up high pressure homogeneous mechanical processing.In addition, the average particle size of the MFCs with the degree of polymerization of 169～805 decreased from 405.0 μm to 62.55 μm with the decrease of the degree of polymerization. The speciflc surface area increased from 2 m2/g to 16 m2/g. The apparent viscosity increased rapidly frorm the initial 40 cP to 1100 cP as the degree of polymerization decreased.Finally, the influence of Fenton - MFC and CMC, cationic microfibrillated cellulose(CMFC) and cationic polyacrylamide (CPAM) on the initial wet strength of the paper were studied. The results showed that the Fenton - MFC and the cationic - MFC all had a good effect on improving the initial wet strength of the paper. Fenton - MFC additions of 6%increased from 1.96 N-m/g (blank) to 5.18 N*m/g at 65% dryness of paper, the wet paper strength increase by about 164%; And the enhancement effect of CMFC was better than that of CPAM. When the dryness was about 53% (the wet tensile strength was 5.75 N·m/g),CPAM additions of 0.15% and 0.5% increased by 14.61% and 65.39%, respectively, while CMFC increased by 30.96% and 72.87%, respectively, compared with the blank sheet. |
