| Nitrocellulose coatings is widely used in the fields of household, vehicle repair paint coating and stationery, etc, due to its advantages of fast drying speed, good decorative performance and easy construction. But the VOC content in the solvent is too high, easy to cause environmental pollution, with the increasing improvement of people’s environmental crisis consciousness, especially the enhancing of environmental regulation by the countries. As environmentally friendly nitro coating product, Waterborne nitrocellulose (WNC) emulsion, with water as dispersion medium, has attracted people’s wide attention and research enthusiasm.In this article, by molecular design, stable and good performance waterborne nitrocellulose emulsion was synthesized, using multi-polymer prepared by the action between Acrylic acid and hydroxy ethyl acrylate as pre-polymer introducing hydrophilic groups. Comprehensive performance of the emulsion and the coating was improved obviously. Then the waterborne nitrocellulose emulsion based on acrylic grafting copolymerization were modified by silane coupling agent KH560. Meanwhile, comparison experiments were also done between waterborne nitrocellulose based on graft ig-copolymerization of acrylic resin and waterborne nitrocellulose after blending modification of acrylic resin. Specific work is divided into three parts as follows:(1) Synthesis of Waterborne Nitrocellulose Emulsion based on Acrylic grafting copolymerization.A new type of waterborne nitrocellulose emulsion was synthesized by introducing the copolymer of acrylic acid and hydroxyl ethyl acrylate, with the method of self-emulsification. The analysis of transform infrared (FT-IR), thermo gravimetric (TGA), particle size distribution, contact angle detection and film mechanical properties test was carried on it. The results showed that there exists good stability of the emulsion and film performance for synthesized emulsion, and the best synthesis condition is that the content of hydroxyl ethyl acrylate (HEMA) is 12% to the total amount of the reactants, the molar ratio of isocyanine (IPDI) and cellulose nitrate (NC) is 0.41:1, the dosage of initiator to total monomer is 0.6%～0.8%. The synthetic waterborne nitrocellulose emulsion was light yellow, particle size of 62.2 nm, natural storage of 90 d. Film water absorption rate of 10.8%, the water contact Angle of 95.26°, the tensile strength of 10.8MPa.Moreover the thermal stability is good.(2) Study on the KH560 modification of Waterborne nitrocellulose emulsion based on Acrylic grafting copolymerization.Waterborne nitrocellulose emulsion modified by KH560 was synthesized successfully. The effect of KH560 content on the properties of the emulsion and film was studied by the analysis of transform infrared (FT-IR), thermo gravimetric (TGA), particle size distribution, TEM, film water absorption rate test and film mechanical properties test. The results showed that property of emulsion and coating film was the best when the content of KH560 to total monomer is 1.2%. Emulsion is light yellow and the blue light, naturally stored more than 90 d. Average particle size of emulsion was 75.73nm. The water absorption rate of the film was 4.5%, the tensile strength was 13.2 Mpa, and the elongation at break was 308.2%. The water resistance, mechanical properties, and stability of the film were improved obviously.(3) Performance comparison between WNC in acrylic acid resin blending modification and acrylic acid resin graft copolymerization modification.The IPDI terminated prepolymer containing hydrophilic group was obtained, with dimethylol propionic acid as hydrophilic reagent, isophorone diisocyanate as hydrophilic chain extender. The hydrophilic group was introduced in nitrocellulose molecule, Using the reaction between IPDI group in hydrophilic prepolymer and Hydroxyl group on nitrocellulose molecule. Then After neutralizing with triethylamine, water emulsification and physical blending with acrylic resin, waterborne nitrocellulose emulsion modified by acrylic resin blending was synthesized. Its properties of emulsion and coating film were determined, and compared with that of acrylic acid grafted copolymer. The results showed the improvement of graft copolymerization modification to the comprehensive properties of the coating film is more remarkable than the result of blend modification. |
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