Preparation Of Curdlan And Nanocellulose Composite Films And The Investigation Of The Properties

Degradable film is a kind of film product made from some native biological macromolecules such as proteins,polysaccharides and lipids in some certain methods.In the process of the degradable film preparation,some intramolecular and intermolecular interactions may occurs between the main raw material.Recently,as a new green and environmental film,degradable film gave rise to the researchers and consumers,because of its exeellent eharacteristies,such as green,environmental protection and biodegradable.However,compared to the traditional petroleum based film products,there are still some defects in the use of performance,such as wet resistance,water resistance performance is poorer,lack of mechanical strength,which limits its application in food packaging,etc.As a natural microbial fermentation polysaccharide,the curdlan has many advantages such as thermal gel properties,good film forming and water insoluble.As the single film material,the mechanical properties of the curdlan film still have to be improved.At the same time,because of its small size,large surface area characteristics,the nanocellulose have showed good mechanical strength in the actual applications,which can be regarded as a good composite film material.Therefore,we hope that the composite film could be prepared to improve the properties of single ingredient degradable film by blending the natural microbial polysaccharides with nanocellulose.In addition,we adopt the hot air drying method to improve the efficiency of film forming which is different from the traditional drying method that dried at 25 eC.And we investigated the effects of water changes during the drying process on the properties of the composite film,expected to provide certain theoretical basis on the rapid drying of biodegradable composite film.To solve the above problems,in this paper,we chose curdlan and nanocellulose as the raw material to prepare the composite film,and studied the change of the composite film properties during the process of hot air drying,research results are as follows:1.The preparation condition of the curdlan/nanocellulose composite film was determined.Investigated the blending ratio between curdlan and nanocellulose of the composite film and the effect of the film liquid9 s pH on the properties of the composite film.Ultimately,determined the best preparation conditions of composite film:blend 95 ml 2%concentration of curdlan solution with a certain amount of 2%concentration of nanocellulose,adjust the pH of the blend liquid to 4.5,add 30%glycerol(w/w)and stir evenly,pour it onto the polytetrafluoroethylene mould(18 cm by 18 cm),peel film after drying under the condition of 25?,RH50%for 24 h.The physical and chemical properties of the curdlan/nanocellulose composite film were tested,including mechanical properties,barrier properties,optical properties and thermal stability.According to the data analysis,when the adding amount of nanocellulose increased to 5%,the composite film showed better mechanical properties and resistance performance.By using microscopic analysis methods such as infrared spectrun(FTIR)and scanning electron microscopy(SEM),obtained the chemical bonding strength and the microstructure change of composite film which could explain the inner change mechanism of the composite film properties.2.The effects of hot air drying conditions on the properties of composite film.During the preparation of degradable film,the drying temperature usually set as room temperature.In order to improve the efficiency of film forming,we explored the hot air drying condition of film forming process and the effects of hot air drying on the properties of composite film:Based on hot air drying(60?,100?)method of film forming process,the effects on properties of the composite film was studied.The results showed that the drying time of the composite film can be shortened from 24 h to 2 h,which greatly improved the film forming efficiency.Compared to the room temperature drying,the composite film still showed excellent mechanical properties when the drying temperature was 60?.The low field nuclear magnetic resonance(NMR)method was used to determine the change of moisture content and moisture state during the drying process of the composite film,which revealed how important the water molecules was during the composite film drying process.