Preparation And Properties Of Self-emulsified Waterborne Nitrocellulose

The solvent-based nitrocellulose coatings was widely used in stationery,car paint repair,home painting and other aspects because of the advantages such as drying fast,high hardness,sandability,easy repair,good decoration and so on.The traditional nitro lacquer and paints with a high Volatile Organic Compounds(VOC)has been limited with the increase of the focus on pollution of environment and current government regulations.Therefore,the waterborne nitrocellulose emulsion(WNC)have attracted more and more attention due to less environmental pollution,less odor,non-combustibility,convenient operation and energy conservation.In this article,NC as a substrate and HDI as a molecular bridge react with DMBA and PA respectively as a hydrophilic reagent a prepolymer,introducing a hydrophilic group into the nitrocellulose molecular chain to synthesize HWNC emulsion and PWNC emulsion respectively by the —NCO on the molecular bridge react with the —OH in the hydrophilic reagent.Meanwhile,polyacrylic acid and HWNC emulsion were physically blended to prepare waterborne nitrocellulose after blending modification of Acrylic acid Polymers(BWNC/PA).The main research contents of this paper are as follows:1.Synthesis and properties of waterborne nitrocellulose emulsion using dimethylolbutanoic acid as hydrophilc agent.A waterborne nitrocellulose emulsion(HWNC)was prepared by selfemulsification with nitrocellulose(NC),hexamethylene diisocyanate(HDI),dimethylolbutanoic acid(DMBA),Dibutyltin dilaurate(DBTDL)and triethylamine(TEA)as main raw materials.The storage stability,particle size and its distribution of the emulsion were tested and its film was characterized by infrared spectrophotometry,thermogravimetric analysis,contact angle detection and mechanical property test.The HWNC emulsion synthesized with HDI1.2110 g,DMBA 1.0100 g,NC 4.3370 g,TEA 0.6881 g and DBTDL 0.0400 g is canary yellow with a particle size of 63.1 nm and stable during the storage atnatural state for more than 90 d.Its film has a water absorption of 9.8%,a water contact angle of 95.7°and a tensile strength of 10.9 MPa,showing an obvious improvement in water resistance,mechanical properties and thermal stability as compared with NC coating.2.Synthesis and properties of waterborne nitrocellulose emulsion modified with polyacrylic grafting copolymerization.A polyacrylic modified waterborne nitrocellulose(PWNC)emulsion was prepared by self-emulsification method with nitrocellulose(NC),acrylic acid(AA),hydroxypropyl acrylate(HEPA)and hexamethylene diisocyanate(HDI)as main raw materials.Then,the corresponding PWNC films were obtained.The effects of molar ratio of AA to HEPA,the amount of azodiisobutyronitrile(AIBN),dosage of HDI and polymerization temperature on the properties of emulsion and film were also studied.FTIR,contact angle measuring instrument,TEM,TGA,SEM,AFM and nano particle surface potential analyzer were use to characterize the chemical structure,hydrophobicity,particle morphology,thermal properties of PWNC films and the particle size of PWNC emulsions.The results showed that when n(AA):n(HEPA)was 3:1,the mass fraction of AIBN was 0.8%,HDI dosage was 5.05 g and polymerization temperature was 80?,the prepared PWNC emulsion colloidal particles were spherical with core-shell structure.The average particle size and polydispersity index(PDI)were 52 nm and 0.102,respectively.The contact angle of PWNC film was 116.3°,which indicated that PWNC film had better water resistance than NC film.3.Synthesis and properties of waterborne nitrocellulose emulsion Blended with polyacrylic acid.The polyacrylic acid(PA)copolymer was prepared by copolymerization of acrylic acid(AA)and hydroxypropyl acrylate(HEPA),and then physical blending with the HWNC emulsion prepared in the first part,waterborne nitrocellulose emulsion Blended with polyacrylic acid.Then,the corresponding BWNC/PA films were obtained.The effects of the amount of PA on the properties of emulsion and film were also studied.FTIR,contact angle measuring instrument,TEM,AFM,TGA and nano particle surface potential analyzer were use to characterize the chemical structure,hydrophobicity,particle morphology,thermal properties of BWNC/PA films and the particle size ofBWNC/PA emulsions,and compared with that 0f waterborne nitrocellulose emulsion modified with polyacrylic grafting copolymerization.The results showed that PWNC performance is better than BWNC/PA.