Influences Of Water On The Properties Of 3-Dimensional Chitosan Material

The low mechanical strength of chitosan material prepared by conventional method is the major factor limits its application in tissue engineering, orthopedic surgery and fracture fixation. 3-Dimensional chitosan materials with high mechanical strength had been prepared via in-situ precipitated method, satisfying potential biomedical utilization. However, water molecules are easily interacted by forming hydrogen bonds with hydrophilic groups in chitosan, the structure and properties of the material is greatly influenced. It is conceivable that the state of water in the chitosan materials is a fascinating subject with theoretical and practical implication. This study characterizes the state of water in the chitosan rod, and different state of water has different effect to the properties of chitosan rod;regenerated fiber is used to reinforce the strength of chitosan material;3-Dimensional chitosan plate is prepared to broaden its application in medical field.1. 3-Dimensional chitosan material with high strength was prepared via in-situ precipitated method, satisfying its application in different position in medical field. Due the good flexibility of the chitosan membrane, re-molds gel rod to be plate before it is completely precipitated. Original molding and after treatment method was used. Unique method may be utilized to prepare complex shape of 3-D chitosan material.2. 3-Dimensional chitosan material with high strength was prepared via in-situ precipitated method. Modeling of the modulus and strength of chitosan rod with the Fermi's equation for the fall in modulus and strength as a function of water content under isothermal condition was fitted. Water molecules attach themselves to hydrophilic side groups, disrupting inter and intra molecular hydrogen bonding, and selective inhabiting interspaces between the layers. It is evident that three types of water exist in the water saturated chitosan rod: Bound water, intermediate water and free water, and the activation energy which are 9.1 kcalmol"1, 5.6 kcal mol1, 1.7 kcal mol'1. Initially, there exists thermal stable bound water that can not be easily removed at temperature of 60 °C. Interaction between water and chitosan results in a strengthening of the hydrogen bond network. Subsequent absorbed intermediate water, acts as a plasticizer, forming water-water bridges that loosen the hydrogen bond network. Differ to other chitosan blends;this intermediate undergoes no thermal phase transition over the range of temperatures normally associated with bulk water. In the later stages of water sorption, water enters the chitosan and loosely adhered as free water which is freezing, having few effects on the mechanical properties of chitosan rod.3. The chitosan blends with cellulose fiber homogeneous dispersed is obtain through in-situ precipitation method. Cellulose fiber is dissolved in trifluoroacetic acid then regenerates. Relative low concentration of the cellulose fiber contributes to the obvious enhancement the mechanical strength of the blends, about 50 % contrast to the pure chitosan rod, resulting from the Physical network formed and chemical (main hydrogen bonding) attachment between the chitosan and cellulose.