| Paper and paperboard are one of the most widely used packaging materials in the world,with excellent biodegradability and mechanical properties.However,the hydrophilic nature and porous structures make paper a poor barrier for water vapor,which limits the use of paper for high barrier packaging application.Conventional approaches for improving the water vapor barrier property of paper are facing significant challenges due to sophisticated processing and recycling problems.It is necessary to develop a new kind of paper packaging material which possesses an improved water vapor barrier property in an environmentally friendly way.In this paper,by using biodegradable nanocellulose crystals(NCC)as a stabilizer and hydrophobic epoxy soybean oil acrylate(AESO)as an oil phase,a stable water-in-oil NCC/AESO emulsion was prepared based on Pickering technique.The prepared emulsion was coated on paper to improve the water vapor barrier performance of paper by synergistic action of AESO hydrophobicity and NCC high crystallinity.This subject mainly studied the synthesis of AESO,the preparation of NCC/AESO Pickering emulsion and the application of NCC/ AESO Pickering emulsion in paper barrier coating.The research content and results are as follows:(1)Optimization of AESO synthesis conditions: Using epoxy soybean oil(ESO)and acrylic acid(AA)as raw materials to synthesize AESO polymer monomers.The effects of the ratio of ESO and AA,amount of polymerization inhibitor,amount of catalyst,reaction time and reaction temperature on the esterification rate and viscosity of AESO were investigated.By measuring the esterification rate and viscosity of the final product,the best conditions for synthesis were determined: the ratio of reactants was epoxy: carboxyl = 1.2:1,the catalyst content was 1.5%,the amount of polymerization inhibitor was 0.1%,the reaction temperature was 110oC,and the reaction time is 8 hours.(2)Preparation of Pickering emulsion and stability study of the emulsion: NCC with high crystallinity was prepared by mechanical method,and NCC/AESO Pickering emulsion was prepared with NCC as solid stabilizer.The effects of NCC concentration and oil-water ratio on the stability of the emulsion in Pickering emulsion system were mainly explored.The best conditions for obtaining oil-in-water AESO emulsion were: oil-to-water ratio 1:9,NCC concentration 1.0%,emulsifier speed 10000 r/min,and emulsification time 3 min.(3)The curing properties of NCC/AESO Pickering emulsion and its application in improving the water vapor barrier properties of paper: The initial reaction time and initial reaction temperature of the AESO curing system were explored.The effects of curing time,curing temperature and initiator dosage on the AESO curing reaction were discussed.The best curing conditions of AESO were: the dosage of initiator was 3.0%,the curing temperature was 90 ?,and the curing time was 2 h.NCC/AESO Pickering emulsion was coated on the filter paper,and the influence of the coating amount on the surface morphology,wettability,moisture permeability and mechanical properties of the coated paper was explored.After coating with NCC/AESO Pickering emulsion,the surface is smoother than the base paper,and the water vapor transmission rate is reduced by 30.1%,at 38? and 90% relative humidity.Compared with the base paper,the elastic modulus of the coated paper is increased by 21.4%,the tensile strength is increased by 47.6%,and the elongation at break is increased by 63.1%. |
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