| Chitosan(CS) is a kind of biologic polysaccharides with many excellent properties, such as moisturizing effect, antimicrobial properties, biological activity, biocompatibility and biodegradable, etc. Therefore, chitosan has attracted much attention in the field of biomedical materials, which prompted that the research and application of chitosan. Chitosan fibers can be used for the preparation of medical dressings, absorbable surgical sutures and tissue engineering carrier materials, etc. However, the strength of the chitosan fiber is generally low, which seriously limits its application scope and application value. So, it is very meaningful for chitosan fiber to improve its mechanical properties.Cellulose nanocrystals(CNC) is a kind of biologic reinforced material with similar chemical structure with chitosan. It has many excellent properties, such as high strength, high modulus, high length-diameter ratio, renewability, biodegradability, etc. So, it is considered to be a highly efficient reinforcing filler with broad application prospects as the carbon fiber, carbon nanotubes.Firstly, chitosan/CNC composite films were prepared via solution casting technique. We studied if the CNC had enhancement effect to chitosan films; And then, we studied the rheological properties of the chitosan solution and chitosan/CNC blend solution; Last, on the basis of the research of rheological properties, we studied the wet spinning process of chitosan solution, chitosan/CNC composite fibers were prepared by wet spinning after getting the optimal spinning process conditions, and tested the properties of composite fibers. The main research results were as follows:1.CNC had significant enhancement effect for chitosan films, and the best result was obtained with the tensile strength of composite films from 40 MPa to 92 MPa when CNC content is 10%. SEM images of cross sections exhibited a good dispersion at less percentage of CNC. The FTIR showed that exsistence of hydrogen bonds between CNC and chitosan molecules. From the XRD patterns of composite films, the addition of CNC influenced the crystallinity of chitosan when solution casting.2.We studied the rheological properties of chitosan solution and chitosan/CNC blend solution. The results showed that chitosan solution gradually deviate from the Newton fluid into pseudoplastic fluid with the increase of mass fraction of chitosan; The processing temperature of chitosan solution around 40°C is advisable; Chitosan/CNC blend solution showed pseudoplastic fluid behaviour. It is indacated that there was a great impact for the rheological properties of chitosan solution by adding CNC to chitosan solution. With the increase of CNC content, the apparent viscosity of the blend solution increased, the non-newtonian index decreased, the viscous flow activation energy decreased, and the structural viscosity index decreased. The rheological law of blend solution was in line with Cox-Merz rule, but the rheological law of the blend solution of the CNC content is 10% deviated from the Cox-Merz rules which is adverse for processing of blend solution. The energy storage modulus and loss modulus of the blend solution have a intersection point, and the intersection point moved to the high frequency area with the increase of temperature. By the formula of Cross and Arrhenius equation, it is concluded that the viscous flow activation energy of the chitosan/CNC blend solution is 24.41~63.29KJ/mol.3.Through the wet spinning process research of chitosan solution, the main spinning process condition were determined: spinning temperature is 40°C, coagulation bath is 5% NaOH solution and 95% ethanol solution, and the volume ratio is 1, plasticization draw ratio is 1.41, washed draw ratio is 1. The chitosan fiber and chitosan/CNC composite fibers were prepared by wet spinning. The results showed that the breaking strength of chitosan fiber is 1.42CN/dtex, the addition of CNC had obvious enhancement effect for chitosan fiber, and the breaking strength of compertise fiber reached 1.76CN/dtex. |
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