Preparation, Properties And Characterizations Of Chitosan-Based Film Materials

The environmental problems such as energy crisis and white pollution are increasingly serious. Chitosan is considered to be one of ideal biomass materials because of its good biodegradability. With unique antibacterial properties, excellent film-forming properties and biocompatibility, chitosan in food packaging and preservation has great prospects for development.But chitosan film has some drawbacks such as poor physical and mechanical properties and high cost of production which limit the application in food packaging and preservation. The properties of chitosan can be enhanced and the production cost can be reduced if other materials were introduced into chitosan. In this study, starch, cellulose and its derivatives, titanium dioxide were incorporated into chitosan. Chitosan/starch edible film, chitosan/cellulose antibacterial film and chitosan/titanium dioxide (TiO2) preservative film were then elaborated and properties of films are discussed.The structure of chitosan-based film was assessed through Fourier transform infrared spectroscopy, X-ray deffraction, scanning electron microscopy, thermal analysis and particle laser analyzer. The interaction mechanism of the various components in the blend films was discussed.The main conclusions are as follows:(1) Sodium carboxymethyl cellulose (CMCNa) significantly improved the toughness of the chitosan/starch edible film and the elongation-at-break of blend film increased by4.5times. The methyl cellulose (MC) enhanced the tensile strength of chitosan/starch edible film which increased by71%. The two edible films Immersed in alkaline solution keep the same shape. The antibacterial rates of the two edible films to bacillus coli and staphylococcus aureus were all more than90%. There was the strong ionic bond connection between NH5+and COO-in chitosan/starch/CMCNa film and polymer electrolyte was generated.The strong hydrogen bonding occurred among MC, chitosan and starch.(2) Microcrystalline cellulose (MCC) was processed by ultrasonic at50W for60min. Compared with the unactivated MCC, its dissolution time decreased by87%and solubility increased by1.3times. The hydroxy association strength decreases and free hydroxyl increased in the samples after the activation treatment. The optimized preparation process of chitosan/cellulose antimicrobial film in an aqueous solution of sodium hydroxide (NaOH)/urea/thiourea was obtained. Amixture of an aqueous solution was prepared by directly mixed NaOH/urea/thiourea in the ration8.0/8.0/6.5(w/w/w).2.5wt%cellulose was completely dissolved in the solution and then3.6wt%water-soluble chitosan was added. The resulting solution was cast onto a plate to get films which were immersed into5wt%Na2SO4/5wt%H2SO4coagulation liquid,0.5wt%NaOH solution,10%glycerol solution sequentially and were air-dried at room temperature. Compared with chitosan films, the tensile strength and elongation-at-break of chitosan/cellulose antimicrobial films elaborated under the acidic system increased by16.7%and5times respectively. Chitosan/cellulose antimicrobial films elaborated under the alkaline system had good flexibility and softnesses of antimicrobial films and toilet paper (first class) were roughly same. The antibacterial rates of the two antimicrobial films to bacillus coli and staphylococcus aureus were all more than99%.(3) Titanium dioxide (TiO2) was modified by ultrasonic and anionic surfactant (sodium laurate). Compared to unmodified TiO2, the average particle size decreased by21.4%, the lipophilic degree increased by24%. Compared with chitosan films, the tensile strength and elongation-at-break of chitosan/TiO2preservative films elaborated by direct blending method increased by50.4%and9.6times respectively. The tensile strength of chitosan/TiO2preservative films elaborated by Sol-gel method was higher than that of films by direct blending method, increasing by34%. The oxygen and carbon dioxide transmission rate of sol-gel films were lower than that of direct blending films, decreasing by73.7%and46.7%respectively. The preservative life of tomatoes packed in sol-gel films was extended from6days to11days. There was strong hydrogen bonding among-NH2,-CH,-OH and TiO2in chitosan/TiO2preservative films. TiO2in the sol-gel films was amorphous. In addition to free water, there was bound water connected with-NH2,-OH in the sol-gel films.The paper firstly comparatively studied the different effects of CMCNa and MC on properties of chitosan/starch edible films. Preparation process of chitosan/cellulose antibacterial film for inner cushioning packaging material in an aqueous solution of NaOH/urea/thiourea is provided. The paper prepared chitosan-based preservative films using TiO2after modification which extend the preservative life of fruits and vegetables and studied the mechanism of action of TiO2and chitosan in the sol-gel films.