Study On The Preparation And Properties Of Nano Cellulose/Ethyl Cellulose Degradable Packaging Film

Ethyl cellulose(EC)is a derivative of cellulose,which has the advantages of good film-forming,high mechanical strength,biodegradation and excellent processing performance.EC is a green material that can be completely d degradable,however,the drawbacks like fragile and stiffness of EC membrane products limits its application in packaging field.Plasticizers are often needed to improve the flexibility of EC in application,but a large amount of plasticizers will lead to the degradation of its mechanical properties.In order to solve this problem,nanocellulose(CNC)which with high mechanical strength was extracted from agricultural Waste——tobacco stem,then modified and added to EC to prepare flexible and high-strength nanocomposites.In order to further improve the performance of the membrane,crystalline EC composite membrane,barrier EC membrane,bubble EC membrane and microporous foaming EC membrane were prepared on the basis of EC nanocomposite membrane.(1)Firstly,soil burying treatment was carried out for tobacco stem,and the influence of burying treatment on the content of components in tobacco stem was analyzed.Then,the cellulose of tobacco stem was prepared by simple purification method and the purity of cellulose was compared with the cellulose that extracted from untreated tobacco stem.The results showed that the contents of benzene/ethanol extractives,lignin and hemicellulose in tobacco stem decreased as the increase of burying time,but the contents of cellulose changed little in soil burying.The purity of cellulose can reach 90.8%with a sample purification method after the tobacco stem burying in soil for 100 day.The properties of nanocellulose prepared from tobacco stem cellulose treated by acid hydrolysis and high pressure homogenization were compared.The results showed that the CNC prepared by acid hydrolysis was "rodlike",with a length diameter of 15-20 and a crystallinity index of 78.4%,and the CNF prepared by high-pressure homogenization method was "filaments",with length diameter ratio is more than 50,and its crystallinity index is 61.8%.(2)The surface of CNC was modified by natural plasticizer epoxy soybean oil(ESO)to prepare ECNC which can be stably dispersed in organic solvent,and then it was added to EC together with epoxy soybean oil.The ECNC/EC nanocomposite film was prepared by solution casting method,and the effect of the amount of CNC on the mechanical properties,thermal properties and optical properties of the composite film was studied.The results show that the addition of ECNC can make up for the decrease of mechanical strength caused by the addition of ESO,and the mechanical strength of ECNC/EC composite membrane increases with the increase of ECNC content.When 20 phr ESO and 4 phr ECNC are added,the tensile strength and elongation at break of ECNC/EC film were increased by 12.9%and 3.8%respectively.The addition of nanocellulose can improve the thermal stability of EC film,and has little effect on the transparency of the film.When 4 phr ECNC is added,the transmittance of ECNC/EC nanocomposite film can still reach 90%in the visible light region.(3)The crystalline EC-PCL copolymer with better flexibility was prepared by ring opening polymerization of ε-CL on the EC molecular chain.The ECNC/EC-PCL nanocomposite membrane was prepared by adding ECNC to EC-PCL copolymer.The relationship between the addition of ε-CL and the properties of EC-PCL copolymer was studied.The effects of the addition of ECNC on the crystallization,thermal and mechanical properties of ECNC/EC-PCL nanocomposites were investigated.The results show that only when the molar ratio of ε-CL to EC structural unit is more than 10:1,the EC-PCL copolymer can form stable and complete crystal.ECNC can not only improve the mechanical properties of EC-PCL copolymer,but also promote the crystallization and melting point of EC-PCL copolymer as a nucleating agent.When 4 phr ECNC is added to EC-PCL copolymer whose molar ratio of ε-CL to EC structural unit is more than 10:1,the tensile strength and the elongation of ECNC/EC-PCL film can reach 45.3 MPa and 13.8%,and its crystallinity and melting point can be increased by 18.0%and 7.1℃ respectively.(4)The lamellar structure of zirconium phosphate(α-ZrP)was prepared by sol refluxing method firstly,and the lamellar structure of zirconium phosphate(E-ZrP)with EC molecular chain was prepared by intercalation and modification.Then,E-ZrP was added to ECNC/EC membrane to investigate the effects of E-ZrP addition on the mechanical properties,optical properties and barrier properties of E-ZrP/EC nanocomposite membrane.The results show that the tensile strength of E-ZRP/EC nanocomposite film can be improved by adding E-ZRP,the tensile strength of E-ZrP/EC film increases by 28.8%when 3 phr E-ZrP is added,but the elongation at break decreases with the increase of E-ZrP content.Adding E-ZrP can greatly improve the barrier of EC nanocomposite membrane,and Adding 3 phr E-ZrP,the oxygen permeability and water vapor permeability of E-ZrP/EC nanocomposites decreased by 83.7%and 81.5%,respectively.Adding E-ZRP can reduce the transmittance of EC film in the ultraviolet region,but not in the visible region.(5)The ultra-fine NaCl particles were prepared by supersaturated solution precipitation method.After surface modification,the NaCl were added to ECNC/EC solution and make films by solvent casting.Then the film was soaked in water to dissolve out the NaCl and prepared ECNC/EC foamed membrane with a large number of pores inside.The effect of NaCl content on the mechanical properties of ECNC/EC foamed membrane was studied.The results show that the size of NaCl particles is smaller and more uniform when the surfactant is added in the preparation of ultra-fine NaCl particles.FTIR and XPS showed that there are a lot of free hydroxyl groups on the surface of NaCl crystal,which can be modified by KH570.The flexibility of ECNC/EC membrane was greatly improved after bubble holes were introduced.The elongation at break of ECNC/EC membrane increased from 12.7%to 23.4%by using 8 phr NaCl as pore making agent,and the number of folding resistance increased nearly 5 times.(6)Firstly,the surface of CNC was modified by IPDI,then the modified CNC,IPDI and MDI were added to ESO/EC solution,and the EC composite membrane was prepared by casting.Then,the EC composite membrane was soaked in water for foaming and prepared I-CNC/EC microporous membrane which with a large amount of pore diameter that less than 1 um.The effect of IPDI content on the performance of I-CNC/EC microporous membrane was studied.The results show that the pore size of I-CNC/EC microporous membrane increases with the increase of IPDI content.Adding 4 phr I-CNC and 12 phr IPDI into ESO/EC composite membrane,the pore diameter of I-CNC/EC microporous membrane is about 0.74 um,its tensile strength,elongation at break and folding resistance times is 40.3 MPa,52.2%and 2193 times.