Single/Double Organic Modification Of Chitosan And Its Effect On Intercalation Of Montmorillonite

Paper is one of the earliest packaging materials,because of its light weight,easy to carry and transport,recyclable and biodegradable characteristics such as product packaging has been widely used in all walks of life.However,water and gas barrier properties are usually very poor due to the hydrophilic of fiber and porosity of paper,limiting its applications in some packaging.In order to meet the requirements of environmental friendly and green packaging,renewable and biodegradable natural polymer barrier coating gradually replace the impregnation processing,paper-plastic composite and other ways to become a main research trend of barrier.Chitosan(CTS)as a kind of renewable and biodegradable natural biopolymer and its non-toxic,antibacterial and film-forming properties,can be applied to coating on paperbased packaging materials.It is expected to achieve a good barrier performance with the layered silicate composite.In order to solve the problem that chitosan can not be directly dissolved in water,the preparation of water-soluble derivatives of chitosan was studied.Then using chitosan and its water soluble derivatives/montmorillonite composite materials on paper barrier coating,and discussed the water resistance and gas barrier properties.Also compared the chitosan/montmorillonite,water-soluble derivatives/montmorillonite composite material effect on the barrier property.The main results are as follows:1.The modification of carboxymethylation or quaternization for chitosan had been studied with monochloroacetic acid(ClCH2COOH)or 3-chloro-2-hydroxypropyltrimethylammonium chloride(CTA)as grafting agent for modification.Based on the effect of carboxymethyl chitosan(CMC)and quaternary ammonium chitosan(CTACTS)on the intercalation of montmorillonite,the synthesis conditions were optimized.The optimum condition for synthesizing the CMC was as following: the reaction time was 6.0h,reaction temperature was50.0?,m(ClCH2COOH)/m(CTS)was 3.0,m(NaOH)/m(CTS)was 4.5.The optimum condition for synthesizing the CTACTS was as following: the reaction time was 10.0h,reaction temperature was 75.0?,m(CTA)/m(CTS)was 4.5,m(NaOH)/m(CTS)was 0.8.The product was also characterized by FT-IR and 1H-NMR spectroscopy respectively.FT-IR and 1H-NMR results showed that carboxymethyl groups and quaternary ammonium groups were successfully introduced into chitosan.And the chitosan derivatives had good water solubility.While the structural characteristics of chitosan and its derivatives/montmorillonite composite were also characterized by TEM.2.Modification of quaterisation was being done for the CMC and of carboxymethylation was being done for the CTACTS,the synthesized conditions of second modification for chitosan were optimized through orthogonal experiment.The intercalation effect of amphoteric chitosan on montmorillonite was regarded as the analytical standard.The optimum conditionfor the quaterisation of CMC were as following: the reaction time was 8.0h,reaction temperature was 60.0?,m(CTA)/m(CMC)was 2.0,m(NaOH)/m(CMC)was 0.4.The optimum condition for the carboxylation of CTACTS were as following: the reaction time was5.0h,reaction temperature was 50.0?,m(ClCH2COOH)/m(CTACTS)was 0.5,m(NaOH)/m(CTACTS)was 0.34.The results of FT-IR and 1H-NMR analysis had showed that CMC quaternized with CTA as quaternizing agent could bring quaternary group into CMC.In the meantime,CTACTS carboxymethylated with monochloroacetic acid as carboxymethylating agent could bring carboxymethyl group into CTACTS.There was a strong typical zwitterionic properties for the product that modified with both carboxymethylation and quaterisation.3.Chitosan and its derivatives / montmorillonite composites were used for barrier coating.It can be seen from the morphology analysis that the surface of the coated paper is covered by the composite coating and becomes more smooth.The contact angle and PDA results show that the water resistance of the coated paper is weakened,which is mainly determined by the hydrophilicity of the coating.According to the test results of the paper's air permeability and WVTR,the barrier property of the coated paper is improved.Combining the above analysis results,the barrier property of carboxymethyl chitosan / montmorillonite composite coating on paper is similar to that of chitosan / montmorillonite composite coating,which is better than the other three.Therefore,carboxymethyl chitosan can be used instead of chitosan,which not only can achieve the same barrier effect,but also solves the problem that chitosan can not be directly dissolved in water.