| At present,the extensive use of plastic packaging materials poses a serious threat to the environment and human health,so it is very important to seek sustainable and environmental packaging materials.Paper/cardboard is the ideal packaging material,with a wide source of raw materials,low cost,recyclable and compostable characteristics,so"paper instead of plastic"has become the research hotspot;However,due to its porous structure and fiber hydrophilicity,paper-based materials lead to poor barrier properties（low water and oil resistance,high permeability to gas and water vapor）,which limits the application of paper-based materials in the field of"plastic replacement".In order to meet the requirements of high barrier packaging,the paper base surface is usually coated with polymer composite coating,or inserted into the water/gas blocking inorganic nano filler,to prolong the penetration path of gas molecules,enhance the gas barrier performance.In this paper,based on the gas penetration model and theory,polymer coating on paper based materials,and by adding spherical nano Si O2inorganic filler,solve the orientation of the lamellar material and difficult to peel off,so as to achieve high barrier to oxygen/water vapor.（1）Coating solution was obtained by mixing polyvinyl alcohol（PVA）and melamine formaldehyde resin（MF）on the basis of low-gram paper.Under acidic conditions,the molecular hydroxyl group of MF and PVA formed a dense cross-linked structure under the action of hydrogen bonding,the intermolecular accumulation was more dense,the water absorption rate decreased,the crystallinity increased,the amorphous region decreased,and the thermal stability,mechanical properties and oxygen resistance performance were improved.The experimental results show that when the coating amount is 15±1 g/m2,the void between the fibers can be completely filled,and the binding between the fibers is enhanced,and the oxygen resistance OTR is 0.384 cm3/cm2·24h·0.1MPa.The oil proof performance is greatly improved,and the Kit value reaches the maximum level 12;When MF content was 7%of PVA,the tensile strength of coated paper was 95.41 MPa,elongation at break was 5.10%,tensile strength was 3.96 KN/m,tear was 228.73 m N·m2/g,and flexural strength was420 times.Waterproof performance Cobb（60 s）is 32.07 g/m2.When starch was used to replace part of PVA,the mixed components showed good compatibility,and the tensile strength and elongation at break gradually increased.The addition of PVA improved the film forming ability of starch,and the oxygen resistance OTR was 0.728cm3/cm2·24h·0.1MPa.The addition of starch not only reduces the cost,but also shows excellent mechanical properties and barrier properties.（2）In order to solve the disadvantages of difficult orientation control and peeling when the traditional two-dimensional lamellar material is used as intercalating material,spherical nano-Si O2particles are used as inorganic filling material.Monodisperse nano-Si O2microspheres were prepared by seed method,coated with dopamine,and then 3-aminopropyl triethoxysilane（APTES）was added.The APTES monomer was self-condensed by Schiff base reaction,and the amino group of APTES monomer was covalently connected with the benzoquinone structure outside Si O2@PDA.A dense APTES-Si O2@PDA inorganic coating layer is obtained.And using emulsion polymerization method to synthesize polyacrylate emulsion,acting as the outer protective layer.The experimental results show that the barrier of the paper based on APTES-Si O2@PDA is greatly improved,OTR is 0.376 cm3/cm2·24h·0.1MPa,especially the water vapor transmittance（WVTR）is reduced to 4.1109 g/m2·24h.At the same time,the mechanical properties have been greatly improved,the tensile strength and elongation at break reach 56.10 MPa and 6.96%,the tensile strength reaches 10.04 KN/m,the tear is 655.10 m N·m2/g,and the flexural resistance is 1250times.The water resistance of coated paper has also been greatly improved,Cobb（1800 s）is 0.77 g/m2;Thermogravimetric analysis showed that the addition of inorganic nano filler improved the thermal stability of the paper.（3）The paper base was coated with fully biodegradable polylactic acid（PLA）and PVA.The nano particles were inserted into the PLA coating to improve the barrier performance of the degradable composite coating film.The experimental results show that the oxygen resistance OTR of the composite coating film is 0.551cm3/cm2·24h·0.1MPa,WVTR is 5.8846 g/m2·24h,tensile strength is 93.01 MPa,elongation at break is 8.61%,tensile strength is 11.92 KN/m.The tearing degree was502.02 m N·m2/g,and the bending resistance was 579 times.Water resistance Cobb（1800 s）is 1.33 g/m2.PLA and PVA have good biodegradability,and the degradation performance of the composite film was buried in the soil of natural environment.The degradation rate in five months was reached,which provided a new idea for solving resource shortage and environmental problems. |
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