Synthesis And Performance Characterization Of Sulfonate Waterborne Nitrocellulose Dispersion

The nitro paint has excellent performances such as easily repaired,higher hardness of the films,drying fast,simple construction,and the construction process of the film defects were handled through grinding,rubbing the wax polish.Besides the nitro paint has excellent outdoor weathering and good decoration.Therefore,it was widely used in interior decoration,leather finishing and play an important role in cars,light industry products,machinery and so on.However,traditional nitro paint was solvent-borne coating and its volatile organic compounds(VOC)content was higher than the request of standard.A large number of the traditional nitro paint resulted in not only the waste of resources and environment polluted,but also a great threat to the health of construction workers and consumers.So the use of traditional nitro paint was limited,and it's urgency to using water to replace expensive organic solvents of polluting environment.The environmental nitro paint that was using water as the dispersion medium will become the development trend.It's very important to modify nitrocellulose emulsion that becomes hydrophilic,because the nitrocellulose emulsion is the main film forming material of nitro paint.Refer to a large number of domestic and foreign literature,in order to improve the comprehensive performance of waterborne nitrocellulose(WNC)emulsion and coating,this paper uses sulfonic acid as hydrophilic groups and hydroxyl,amino groups as reaction groups reacting with isocyanate groups through molecular design,and then hydrophilic prepolymer of isocyanate terminated is produced.The isocyanate groups of the hydrophilic prepolymer reacts with hydroxyl groups of the nitrocellulose,which hydrophilic groups can be introduced to the nitrocellulose molecule.Therefore the sulfonate waterborne nitrocellulose emulsion of good performance and stability will be prepared.This emulsion has self-emulsifying function,uniformly dispersed in water,and would form small and uniform particle size of the emulsion.For the sake of further improving comprehensive properties of the waterborne nitrocellulose emulsion,the paper uses polyvinyl alcohol(PVA)to blend modification for synthesized sulfonate waterborne nitrocellulose emulsion,which has prepared the polyvinyl alcohol modified sulfonate waterborne nitrocellulose(PVA/ASWNC)composite emulsion with the properties of polyvinyl alcohol and sulfonate waterborne nitrocellulose emulsion.Specific work is divided into the following three parts:(1)Synthesis and Performance Characterization of Sulfonate Waterborne Nitrocellulose Dispersion with N,N-bis(2-hydroxyethyl)-2-aminoethyl sulfonic sodium as hydrophilic chain extenderThe hydroxyl sulfonate waterborne nitrocellulose emulsion(HSWNC)was prepared by self-emulsification with N,N-bis(2-hydro xyethyl)-2-aminoethyl sulfonic sodium(BES-Na)as hydrophilic chain extender and isophorone diisocyanate(IPDI),nitrocellulose(NC)as the main raw material.The optimum reaction conditions was received by exploring the molar ratio of IPDI and NC,the content of BES-Na on the particle size of the emulsion and film properties:the molar ratio of IPDI and NC was 0.83:1,the content of BES-Na was 15%.Under the optimum conditions it was tested that the average diameter of emulsion was 37.4 nm,PDI was 0.275 and water absorption of coatings was 9.28%.FTIR analysis showed that N,N-bis(2-hydroxyethyl)-2-aminoethyl sulfonic sodium had been grafted onto nitrocellulose and the original structure of nitrocellulose molecule didn't be destroyed.TGA analysis demonstrated that the HSWNC film was higher thermal stability compared with nitrocellulose.The water resistance of HSWNC films was well.(2)Synthesis and Performance Characterization of Sulfonate Waterborne Nitrocellulose Dispersion with 1,5-bis aminos-3-sulfonic sodium as hydrophilic chain extenderThe amino sulfonate waterborne nitrocellulose emulsion(ASWNC)was prepared by self-emulsification with 1,5-bis aminos-3-sulfonic sodium as hydrophilic chain extender and isophorone diisocyanate,nitrocellulose as the main raw material.The optimum reaction conditions was received by exploring the molar ratio of IPDI and 1,5-bis aminos-3-sulfonic sodium,the content of nitrocellulose on the particle size of the emulsion and film properties:the molar ratio of IPDI and 1,5-bis aminos-3-sulfonic sodium was 1.20:1,the content of nitrocellulose was 12%.Under the best experiment conditions it was tested that the average diameter of emulsion was 45.52 nm,PDI was 0.136,water absorption of coatings was 10.3%and the surface of the ASWNC coatings was smooth.FTIR and XPS analysis proved that 1,5-bis aminos-3-sulfonic sodium had been successfully grafted to nitrocellulose.TGA analysis showed that the ASWNC coatings was higher thermal stability compared with nitrocellulose.(3)Properties of waterborne nitrocellulose emulsion modified by polyvinyl alcoholPVA/ASWNC composite emulsion was prepared by physical blending with amino sulfonate waterborne nitrocellulose emulsion(ASWNC)and polyvinyl alcohol(PVA).The effects of PVA content on the properties of composite emulsion and film was investigated through emulsion stability test,measurement of particle distribution,water contact angle,water absorption and mechanical properties of the films test.The result suggested that when the PVA content is 5%,PVA/ASWNC composite emulsion had good storage stability at room temperature,and the tensile strength of the film was 10.4 MPa,the elongation at break was 359.4%.The prepared PVA/ASWNC composite emulsion in optimal conditions were comparative studied to ASWNC emulsion by Scanning electron microscope,Fourier transform infrared spectrometer,Transmission electron microscope and Thermo gravimetry analysis.Compared with the ASWNC emulsion,the particle size of PVA/ASWNC composite emulsion decreased,and the thermal stability and mechanical properties of the film were improved.