| Traditional solvent-based nitrocellulose coatings have been widely used due to their fast drying as well as excellent properties in decoration.However,solvent-based coatings with high volatile organic compounds(VOC)is a great threat to the human health and environmental protection.Therefore,water-based coatings have become the main direction in polymer materials field due to its water as solvent,low VOC and environmental-friendly.A new generation of hydrophilic agent(DMBA)was introduced in the study.Waterborne polymer emulsion was prepared by self emulsification using the NC and CA as film-forming material,DMBA as hydrophilic agent.Thus,the hydrophilic carboxylate group was introduced into the cellulose molecule by the interaction of hydroxyl group(-OH)with isocyanate group(-NCO).In order to improve the overall performance of emulsion and coating,waterborne nitrocellulose emulsions was prepared by AA,HEMA and FA copolymers as hydrophilic groups.The main research work s is as follows:(1)Preparation and properties of waterborne nitrocellulose emulsionwith AA/HEMA/FA copolymers as hydrophilic group(FWNC)With NC,IPDI,AA,HEMA,FA as main raw materials,the FWNC emulsion was prepared by self emulsification.The effects of monomer polymerization temperature,the value of n(AA)/n(HEMA)and the amount of FA on the properties of emulsion and film were also studied.The results showed that the FWNC emulsion showed a stable performance with the particle size of 54 nm and PDI 0.042,When the monomer polymerization temperature was 60 ℃,the n(AA):n(HEMA)was 3:1 and the mass fraction of fluoroacrylate was 1%.TEM analysis demonstrated the particles of emulsion were regularly spherical with a core-shell structure.Compared with WNC films unmodified,the water absorption of the modified WNC films was reduced to 2.0% and contact angle was increased to 120 °,which exhibited the FWNC film has excellent water resistance.(2)Preparation and properties of waterborne nitrocellulose emulsion with DMBA as hydrophilic group(DWNC)With NC,DMBA and IPDI as main raw materials,the DWNC emulsion was synthesized by the self emulsification.The effects of the amount of DMBA,the n(-NCO)/n(-OH)on the properties of emulsion and film were studied and the ingredients used in the preparation was also obtained.When the the mass fraction of DMBA was 12% and the value of n(-NCO)/n(-OH)was 1.03,the DWNC emulsion had a average particle size of 107.3 nm and PDI of 0.123.The emulsion particles showed the core-shell structure in the water phase.SEM,AFM,TGA analysis demonstrated that the DWNC film had a smooth and flat surface and good thermal stability.The mechanical properties of film was improved with the introduction of DMBA,and the tensile strength and elongation at break of film were 15.97 MPa and 230%,respectively.(3)Preparation and properties of waterborne cellulose acetate emulsion with DMBA as hydrophilic group(DWCA)With CA,DMBA and IPDI as main raw materials,the DWCA emulsion was synthesized by the self emulsification.The effects of the amount of CA,the n(IPDI)/n(DMBA)on the properties of emulsion and film were studied and the ingredients used in the preparation was also obtained.When the mass of CA was 3g and the value of n(IPDI)/n(DMBA)was 1.25,the DWCA emulsion had a average particle size of 130.0 nm and PDI of 0.214.The emulsion particles showed the core-shell structure in the water phase.FTIR indicated that the hydrophilic prepolymer were introduced into the CA molecule and the original molecular framework of CA was retained.The film had a low surface roughness and good water resistance with water contact angle of 92.8°. |
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