Preparation And Application Of Grafted Chitosan

In this study, the chemical modification of carboxymethylation and quarternization for chitosan(CTS) had been studied with monochloroacetic acid (ClCH2COOH) and dimethyldiallyl ammonium chloride,2,3-epoxypropyltrimethyl ammonium chloride(ETA) as grafting agent for modification. The chitosan derivates were used to keep fruit fresh and improve paper physical properties.When carboxymenthylated-modification was being done, the synthetic condition of carboxymethyl chitosan(CMCTS) was optimized. The optimum condition for synthesizing the CMCTS was as following: the mass ratio of chloroacetic acid to chitosan was 1∶1.2, basification temperature was 40℃, reaction temperature was 70℃, reaction time was 4h. The CMCTS was white powder, its water solubility is 15g/L and its DS(degree of substitution) approached to 0.809. The viscosity was about 25.5mPa·s. The product was also characterized by FTIR and 1HNMR spectroscopy respectively. The results of FTIR and 1HNMR analysis had showed that the carboxymethyl chitosan were synthesized.The synthetic condition of quaternized chitosan (CTS-DMDAAC and CTS-ETA) was optimized. The optimum condition for synthesizing the CTS-DMDAAC was as following: mole ratio of chitosan/DMDAAC=1∶1, concentration of initiator 0.5mmol/L, 90℃, pH =6, reaction time 3hr. FTIR and 1HNMR confirmed the graft copolymer of dimethyldiallyl ammonium chloride onto chitosan. The GR(grafting rate) of CTS-DMDAAC was about 66.5%. And the optimum condition for synthesizing the CTS-ETA was as following: mole ratio of chitosan/ETA = 1∶4, concentration of initiator 0.5mmol/L, 75℃, pH =7, reaction time 6hr. The GR of CTS-DMDAAC was about 89.3%. FTIR and 1HNMR confirmed the graft copolymer of 2,3-epoxypropyltrimethyl ammonium chloride onto chitosan. The pH stability, water solubility and moisture absorption capability of quarternized chitosan were better than chitosan.The amphoteric chitosan was synthesized by carboxymenthylated-modification of quarternized chitosan. The optimum conditions for the carboxylation of CTS-DMDAAC(amphoteric chitosanⅠ) were as follows: the mole ratio of ClCH2COOH to CTS-DMDAAC was 0.9∶1, basification time was 80min, reaction temperature was 70℃, reaction time 4h. The DS of amphoteric chitosanⅠapproached to 0.53. The optimum conditions for the carboxylation of CTS-ETA(amphoteric chitosanⅡ) were as follows: the mass ratio of CTS-ETA to ClCH2COOH was 1.5∶1, basification time was 60min, reaction temperature was 60℃, reaction time 3h. The DS of amphoteric chitosanⅡapproached to 0.69. FTIR and 1HNMR confirmed the structure of amphoteric chitosan. The pH stability, water solubility and moisture absorption capability of amphoteric chitosan were better than chitosan and quarternized chitosan.Chitosan and its derivations can be used to keep strawberry fresh. The experiments showed that the optimum concentration for keep strawberry fresh were as follow: 1.5%CTS, 0.2%CTS-DMDAAC, 1.5%CMCTS and 1%CTS-ETA. The moisture absorption capability and water solubility of chitosan derivations'film were as follow: CMCTS>CTS-ETA>CTS-DMDAAC>CTS. The effect of keeping fresh in cold was better than under normal temperature. The effect of keeping strawberry was CTS-ETA>CMCTS>CTS-DMDAAC>CTS.The chitosan derivates can be used as papers strengthen agents. The experiments showed that the CMCTS, CTS-DMDAAC, CTS-ETA, amphoteric chitosanⅠand amphoteric chitosanⅡwere all good paper strengthen agents. They can improve the physical properties of handsheets made of softwood pulp and hardwood pulp. The improvement can be achieved by adding only 0.2%-0.3% dosage of the derivates.