Study On Modification And Application Of Pulp Fibers Via Tom Transfer Radical Polymerization

With the development of the paper making industry, the use of chemicals and the degree ofpapermaking white water closed are increasing rapidly. It causes the accumulation of the anionictrash and chemical additives in white water system, and influences the paper production andquality greatly. Application of modified fibers by physical or chemical methods can give thepaper product special properties and make them meet the requirements of papermakingperformance. Compared with chemical adding, using modified fibers can improve waterenvironment, reduce sewage discharge, and have biodegradable advantages in paper production.The application of modified pulp fibers is more and more developing. Atom transfer radicalpolymerization (ATRP)method was first proposed in1995. Because of the advantages that ATRPhas a widely variety sources of the monomer, oxygen impurities resistance, controllablemolecular structure and graft modification does not destroy the skeleton structure of the celluloseetc, it is widely used in the graft modification of pulp fiber, ramie fiber, cotton fiber and so on. Inour studies, the polyisoprene and polyacrylamide were grafted onto pulp fiber surface modifiedfiber and provide with unsaturated carbon carbon bond and amide respectively to the modifiedfibers, Also, the study on the influence of modified fibers on the paper mechanical and Wet-endperformance was made.Before the graft modifying of the pulp fibers, the halogen atoms should be esterificated tothe surface of the pulp fibers firstly, that makes the pulp fibers into macroinitiator. Thepreparation of the macroinitiator directly impacts to the pulp fibers graft-modified. The optimumconditions of the macroinitiator preparation were determined by using FT-IR and EDS. The pulpbeating degree was40°SR by using hardwood pulp. The reaction was performed at40℃for24h.Then the graft polymerization of isoprene was made. Reaction temperature was40℃andreaction time was24h. Catalyst and monomer molar ratio was1:50. Graft rate was highest at theconditions, but only5.36%because of the low activity of isoprene monomer polymerizationthrough ATRP. By FT-IR and TG analysis, polyisoprene has been grafted onto the fiber surfacesuccessfully. The modified fibers were added to the pulp the carbon-carbon double bond by free radical polymerization between the fibers to form crosslinked network structure, and prevent the fibers swell, thus improve the wet strength of paper. As a result of polyisoprene graft rate was not high, the double bond content was less, and the effectiveness of wet strength was increasing not obvious in the study. By scanning the paper by surface electron microscopy, it was found that the paper surface showed a network of cross-linked materials.Meanwhile the effect of different modified fibers on Zeta potential, drainage property, retention of paper pulps and the impact of beating degree on the Zeta potential and the drainage property were studied. The results showed that, with the increase of the amounts of modified fibers Zeta potential decreases gradually, drainage property steadily improved, and there was no apparent influence on retention. When the addition was0.2%, the Zeta potential and the drainage property declined with the increasing of the beating degree.2%of the modified fibers could give better effectiveness with the comprehensive cost consideration. When cationic polyacrylamide (CPAM) was added to the hardwood pulp, the wet-end performance of the pulp was significantly improved.Polyacrylamide was also grafted onto fiber surface and the optimum reaction conditions were:temperature90℃, reaction time24hours, catalyst and monomer molar ratio was1:100. Grafting rate was up to23.9%. By FT-IR and TG analysis, it was found that polyacrylamide was successfully grafted onto the fiber surface. The modified fibers containing amide groups, they can form hydrogen bonds with the hydroxyl groups the in the fibers, to improve the bonding strength of the fibers. It was found that adding6%of the modified fibers gave better effectiveness on dry strength. Dry tensile index increased42.9%, burst index increased21.7%and tear index increased16.9%. Using scanning electron microscopy analysis, it revealed that fibers were in close connection with crosslinking substances that may explain the strengthening mechanism.