Study On Pulp-Enzymolytic Preparation Of Cellulose Nanocrystalls And Its Transparent Composite Membrane

Nanocellulose has a series of advantages such as high specific surface area,high tensile strength,high transparency and reproducibility.At present,cellulose nanocrystals(CNCs,Cellulose Nanocrystals)and cellulose nanofibrils(CNF,Cellulose Nanofiber)are mainly prepared by acid hydrolysis or oxidation combined with mechanical homogenization.However,these methods have disadvantages such as high pollution or high energy consumption.The preparation of nano-cellulose by enzymatic hydrolysis is attracting more and more attention and attention due to its environmental protection,the high efficiency and specificity of cellulase on the substrate.In this paper,the nano-crystalline cellulose was prepared by pulp enzymatic hydrolysis.The controllable and optimized reaction conditions were used to control the preparation of nano-cellulose.Rod-shaped nanocellulose(CNC-L)and spherical nanofibers(CNC-H)were prepared at different enzyme concentrations and reaction time.The performance of the pure nanocellulose membrane prepared by enzymatic hydrolysis and the currently used TEMPO(2,2,6,6-tetramethylpiperidine oxide)oxidation mechanical method was compared.The composite film was prepared by enzymatic hydrolysis of CNC-L and CNC-H and chitosan(CS,Chitosan)solution by a blending casting method according to a certain ratio,by SEM,FT-IR,XRD,thermogravimetric analysis,The nano-cellulose composite membrane was characterized and analyzed by analytical methods such as light transmission performance,mechanical stretching,gas permeability and oxygen permeability.(1)In the range of relatively low enzyme activity(1-50 μ/mL),the prepared nanocellulose is in the form of strips and rods,and the fiber length decreases with time and concentration,and the range is At 300-800 nm,the crystallinity of nanocellulose is improved;(2)Under the condition of relatively high enzyme activity(100-500 μ/mL),the prepared nanocellulose exhibits a microspherical appearance,and the further increase of the concentration causes the rod-shaped fibers to rapidly decrease,and the spherical particle size ranges from 50 to 130 nm.,the crystallinity of nanocellulose is reduced;(3)Both CNC-L and CNC-H prepared by enzymatic hydrolysis can form a film,however,pure CNC-H has poor film-forming property and low film strength,which is related to the spherical structure of CNC-H;CNC-L film formation The tensile strength is 39.45 MPa and 48.92 MPa,respectively,which is lower than that of CNF film.The elastic modulus is higher,which is 6306.05 MPa and 9313.63 MPa,respectively,which is larger than that of CNF film;(4)Compared with the pure chitosan membrane,the CS/CNC composite membrane prepared by the enzymatic hydrolysis of nanocellulose and chitosan solution was improved in some properties,and the mechanical properties of the composite membrane were improved by CNC-L.More,15%of CNC-L increased the film tensile strength by 54.04%,and the elastic modulus increased by 335.8%;1%of CNC-H reduced the composite membrane permeability by 14.1%,and 5%of CNC-H reduced the oxygen permeability.The best results,a reduction of 40.9%.