Preparation Of Guanidine Antimicrobial Agent Under Microwave Radiation And Its Application On Paper

Guanidine antimicrobial agent bearing guanidine group possesses excellentantibacterial performance. Guanidinylated polymers were prepared by grafting guanidineoligomers onto paper-making additives with long chains. This could reduce the loss of smallmolecules of guanidine leading to temporary antibacterial performance and widen theapplication of guanidine antimicrobial agent in papermaking. In this work, guanidinylatedpolymers(CTS-G and PEI-G) were respectively obtained by the reaction betweenpolyhexamethylene guanidine hydrochloride and chitosan or polyethylenimine which arecommonly used as paper-making additives under microwave.The optimal conditions were revealed by independent parameters: molar ratio,microwave heating time and reaction temperature. Compared to conventional heating,microwave assisted processes could reduce the time and increase the efficiency in thereaction of guanidinylated polyethylenimine. The structure comparison between chitosanand guanidinylated chitosan revealed by FTIR and 1H NMR spectra indicated that thePHGC was successfully introduced to the chain of chitosan. From SEM images, the surfaceof CTS-G became irregular and fluffy compared to chitosan, which shows themicrostructure difference happened during the reaction.To investigate the antimicrobial activities of CTS-G, the minimum inhibitionconcentration(MIC)(150ppm) was determined by a serial dilution method initially.Meanwhile, dynamic UV absorption and atomic force microscope were utilized in attemptto reveal the antimicrobial mechanism which was to damage the cell membrane and thenkill the bacteria. From dynamic UV absorption, when the concentration of CTS-G washigher than MIC, the OD260 ratio reached to 1.35 in a short time, implying that most cellmembrane was damaged. Corresponding to the result of UV, the morphologies of bacterialcells treated with CTS-G at the same concentration showed that the cells collapsed andcould not maintain the elliptical shape.Effects of addition dosage and adding methods on paper properties includingantimicrobial activity and physical properties were studied. Three adding methods wereapplied in this thesis such as ordinary internal treatment, pre-impregnated internal treatmentand surface treatment. CTS-G and PEI-G endowed paper with excellent ability to killbacterial. When the dosage of CTS-G added into pulp was higher than 1.0%, theantimicrobial efficiency of handsheet could reach above 90%. According to theantimicrobial activities and enhanced physical properties of paper, it could be concluded thatthe most suitable adding method is pre-impregnated internal treatment. When the additiondosage is 1.2%, the antimicrobial efficiency of paper almost reaches 100% and the wet/drystrength ratio is 21%. Though surface treatment may reduce the strength property due tononuniform spray, it could be a good method to prepare paper which requires temporaryability to kill bacteria.