Influence Of Physical Treatment On The Properties And Structure Of Chitosan And It's Modified Films

Chitosan with excellent biodegradable and biocompatible characteristics is one of the most abundant natural polymers next to cellulose. Chitosan also has a high potential for development into sophisticated functional polymer since it has both free amino groups and hydroxyl groups on its framework, which are easily modified. Due to its unique polymeric cationic character, its gel and film forming properties, chitosan has been extensively examined in the areas of chemical and medicinal industry .The main contents and conclusions in this thesis are as follows:At first, this paper has a review on the research proceeding, current research development and application of films related chitosan and chitin. The properties and structures of these films depend on their molecular weght(Mw), degree of deacetylate (DDA), the solvent, the temperature to remove the solvent from the chitosan solution. Besides, Blending, chemical reaction and physical treatment are important ways to change the properties of films. The chemical crosslinking agents possibly induce Stoxicity and other undesirable effects. To overcome these disadvantages, it is necessary to study the effect of physical treatment on the preparation of films related chitosan.Second, the influence of solvents treatment on the properties and structure of chitosan was investigated. Chitosan films (CSF), chitosan films cross-linked with formaldehyde(CSFF) and chitosan films cross-linked with glutaraldehyde(CSFG) were prepared and treated with ethanol, ether, and petroleum ether, respectively. The experimental results show that the percentage of water sorption and mechanical properties of films were affected by solvent treating; the degree of influence was CSF< CSFG < CSFF. The percentage of water sorption and the elongation increased as the polarity of solvents decreasing. After treated with petroleum ether, the percentage of water absorption and the elongation of CSFF increase by 2.1 times and 82% respectively compared with untreated CSFF.Third, chitosan/gelatin blend films were prepared successfully by solution method. The films were then exposed to moist heat at different conditions for several time intervals. The influence of moist heat treatment on their structures was investigated by Fourier infrared spectroscopy (FT-IR), X-ray diffraction(XRD) and scanning electron microscopy (SEM). After treatment, the percentage of water sorption and dissolution of blend films in both distilled water and acid were gradually decreased .The results reported in this study showed that change in the water resistance of blend films is usually caused by heat-induced change of blend films in crystallinity and/or the formation of crosslinks between the polymer molecules.Forth, chitosan/PVA blend films , prepared successfully by solution method ,were subjected to moist heat treatment at known temperatures or cross-linked with glutaraldehyde, respectively. The structures of films were studied by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction(XRD) and scanning electron microscopy (SEM).The properties of films such as the mechanical properties, the water adsorb percent in different pH solutions were measured. Cross-linking of chitosan/PVA blend films with glutaraldehyde destroyed the crystalline and had a smaller swelling degree. With increasing heating time, the crystalline form of films changed. PH sensitivity of the chitosan /PVA blend films can be changed by controlling both the concentration of the cross-linking agent or the time of moist heat treatment.