| With the development of the society,functional material has been gaining more and more attention.Chitosan is a natural positively charged alkaline aminopolysaccharide,has lots of advantages like antimicrobial activity,excellent biocompatibility and admirable biodegradability,which makes chitosan a research hot spot in the field of biologic material.Pure chitosan profile has a relatively bad mechanical property and is fragile,which restrict the preparation and the application of it.However,the blending profile,prepared by mixing the chitosan solution and polyvinyl alcohol solution and adopting various methods such as dry forming,wet forming and electrostatic spinning,is much better in mechanical property than pure chitosan profile and has a wide range of applications in the fields like biological medicine,environmental protection and food packaging.At present,there are lots of researches focusing on attaching more functions to the chitosan/ polyvinyl alcohol blending profile while a few center on the forming and preparation of the blending film.The wet forming and crosslinking of chitosan/ polyvinyl alcohol blending film are the objects of this paper in order to get a better way to prepare the blending film by wet forming and design its technological parameter.Besides,the properties of the blending film products will be improved through crosslinking.The main research contents of this paper include: the rheological property of chitosan solution and polyvinyl alcohol solution as well as chitosan/polyvinyl alcohol mixing solution;the application of plasticizer and its plasticizing mechanism;the factors which influence the mechanical properties of chitosan/polyvinyl alcohol blending film;the main effect and interaction effect of these factors as well as the design and the preparation of the blending production which is optimized both in breaking strength and breaking elongation;theinfluence of crosslinking modification aftertreatment on chitosan/polyvinyl alcohol film's structure and properties;the property measurement and comparison of three different blending film.Firstly,in this paper,the chitosan solution and polyvinyl alcohol solution having similar rheological property based on the viscosity test result are chosen as raw material and glycerinum are chosen as plasticizer.Then,the chitosan blending film is prepared through a wet formation method.This paper has discussed the impacts of the five factors—blending ratio;plasticizer content;coagulating bath constituent;coagulating temperature;coagulation time—on the mechanical property of chitosan/ polyvinyl alcohol blending film based on single factor experiment and abundant mechanics performance testing.Furthermore,valid first order regression equations of two responses(breaking strength;breaking elongation)are obtained using a full factorial design of DOE.According to the regression equations,this paper has design a chitosan/polyvinyl alcohol blending film.In addition,in order to improve the thermostability of the blending film,glutaraldehyde crosslinking aftertreatment is adopted to the blending film.The structure of chitosan/ polyvinyl alcohol blending films before and after crosslinking are characterized by using Fourier transform infrared spectroscopy(FT-IR),scanning electron microscope(SEM),X-ray diffraction(XRD),thermogravimetry(TG).Finally,this paper conduct experiment to measure and compare the thermostability,antimicrobial activity and hydroscopicity of three different blending film.Following conclusions can be got:(1)According to the viscosity testing,3% chitosan acetic acid solution and 10%polyvinyl alcohol aqueous solution have similar rheological property and are feasible to be blended to prepare the blending film.(2)FT-IR test indicate that glycerinum,chitosan and polyvinyl alcohol do not have chemical interaction between each other.In a certain range,glycerinum has an influence on the mechanical properties of the blending film by affecting the hydrogen bond inside the blending film so that glycerinum has Plasticizing effect.The combination of XRD,SEM,TG test indicate that glycerinum can improve the crystallinity of the blending film and make its surface rougher.Meanwhile,glycerinum makes the decomposition temperature of the blending film lower.(3)According to the mechanics performance testing of single factor experiment,blending ratio,glycerinum content,coagulating bath component,coagulating bath temperature and coagulating time have impacts on the mechanical properties of the blending fiber.Based on full factorial experiment of DOE,the effective value of the factors and their interacting effect value can be got and in the temperature of 25±2?and the humidity of 75±5%,between breaking strength(y1),breaking elongation(y2)and factor A(the mass of 3% chitosan solution,rank:30%~70%),factor B(the glycerinum content,rank:1%~5%),factor C(the mass of saturated sodium sulfate solution in coagulating bath,rank:20%~80%)and factor D(coagulating temperature,rank:25?~45?),the valid first order regression equation can be got:y1=30.03+25.7025A-89.425B+8.042C+0.0414D-191.75AB-0.1376CD;y2=103.9895-49.785A-118.625B-17.14C-0.012D+777.25AB-0.64AD+10.26BD(4)According to the valid first order regression equation,in the temperature of25±2? and the humidity of 75±5%,the technological conditions complying the goal of breaking strength=42MPa,breaking elongation=60% are as follows: the mass of 3%chitosan solution 60%,the glycerinum content 3.6%,the mass of saturated sodium sulfate solution in coagulating bath 30%,coagulating temperature 25?,coagulating time 60 s.(5)Through the crosslinking aftertreatment,the feasible technological conditions are the concentration glutaraldehyde solution 3%,crosslinking temperature 35?,crosslinking time 40 min and it shows rise on the blending film breaking strength and decrease on the blending film breaking elongation.The test results of the FT-IR,XRD,SEM and TG indicate that the Schiff alkali is generated after the interaction between the amidogen in chitosan molecule and glutaraldehyde,that there is a rise on the blending film crystallinity and its heat stability and the blending film surface become rougher.(6)Through heat treatment experiment,antibacterial experiment and hydroscopicity experiment,it indicates that:For the chitosan/ polyvinyl alcohol blending film with glycerinum(GH1),the maximum condition of heat heat-moisture treatment is at temperature 60? and time 30 min and the maximum condition of dry heat treatment is at temperature 100? and time 30 min.Its antibacterial rates for Escherichia coli and staphylococcus aureus are both beyond 99%.Meanwhile,the water absorption of GH1 is10.1%;For the chitosan/ polyvinyl alcohol blending film with glycerinum(GH2),the maximum condition of heat heat-moisture treatment is at temperature 50? and time30 min and the maximum condition of dry heat treatment is at temperature 100? and time 30 min.Its antibacterial rates for Escherichia coli and staphylococcus aureus are both beyond 99%.Meanwhile,the water absorption of GH2 is 12.4%;For the chitosan/polyvinyl alcohol blending film after glutaraldehyde crosslinking(GH3),the maximum condition of heat heat-moisture treatment is at temperature 60? and time 30 min and the the maximum condition of dry heat treatment is at temperature 100? and time30 min.Its antibacterial rates for Escherichia coli and staphylococcus aureus are both lower than 83%.Meanwhile,the water absorption of GH3 is 14.1%.Therefore,the plasticizer,glycerinum,can lower the thermostability and improve the hydroscopicity of the blending film.After crosslinking reaction,the antimicrobial property of the blending film decrease significantly.Having studied the wet forming craft of glycerinum-plasticizing chitosan/polyvinyl alcohol blending film,this paper has a facilitating effect on the industrialized production of chitosan/ polyvinyl alcohol blending film.Meanwhile,this paper provides experimental guidance for the preparation of functional materials.Furthermore,having studied the glutaraldehyde crosslinking on the chitosan/ polyvinyl alcohol blending film,measured and compared the properties of the blending fibers before and after modification,this paper provides a certain theoretical foundation and reference to the aftertreatment modification of chitosan/ polyvinyl alcohol blending film. |
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