| Epoxy resins have important applications in the anti-corrosion coatings for their excellent properties, such as good adhesion, excellent solvent resistance and heat properties, etc. With people's increasing awareness of the environmental protection, waterborne epoxy resins have become more and more important. However, the poor anti-corrosion properties of waterborne epoxy coatings limit its application. In this dissertation, epoxy resin was brought in emulsion system and waterborne epoxy/acrylic composite latex was prepared by miniemulsion polymerization; Waterborne acrylic latex modified by GMA was synthesized; Synthesis condition and curing temperature were studied; Waterborne epoxy/acrylic composite latex was used to prepare the varnish and pigmented coatings. The final coatings are of excellent anti-corrosion properties. The dissertation includes but not limit to the following contents:1. A series of waterborne epoxy/acrylic composite latex with different epoxy resin types and contents were prepared by miniemulsion polymerization. Epoxy resin and (methyl)acrylic monomer were emulsified and dispersed by high pressure homogenization Radical initiator was used to initiate polymerization of acrylic monomers and latex was obtained Effects of pre-emulsification method, emulsifier, functional monomer, initiator, reaction temperature, solid content, epoxy resin type and content on the latex properties were investigated. Fourier transform infrared spectroscopy (FTIR) was used to prove the retention of the epoxy groups; The result of transmission electron microscopy (TEM) test confirmed the core-shell structures of the composite latex particles; Besides, pre-emulsification method and emulsifier are the most important factors to the latex stabilities.2. High mechanical performance films were obtained by the composite latexes in the presence of curing agents. Effects of different epoxy resin types and contents, curing agent types and content to the mechanical properties, crosslinking and water absorption were studied. Results show that the films with E-44 have better properties. Tensile strength, tensile modulus and crosslinking of films increase with epoxy resin content, while water absorption and elongation rate decrease. The addition of curing agent can improve the properties of the films.3. A series of varnish and pigmented coatings were prepared by the composite latexes with different contents of E-44 in different curing temperatures. Anti-corrosion and mechanical properties of coatings were studied by immersion test and salt spray test. Electrochemical impedance spectroscopy (EIS) was used to characterize the electrochemical performances. Results show that the increase of epoxy resin content and curing temperature can improve the performance of coatings. The varnish coatings cured at high temperature have excellent anti-corrosion properties for up to 2000 h.4. Waterborne acrylic latexes with different GMA contents were synthesized by seed polymerization method. Effects of pre-emulsification, emulsifier, protective colloid and GMA content to latex properties were studied. Results show that pre-emulsification and addition of protective colloid can decrease coagulum content. Emulsifier plays an important role in the latex stabilities. The latex stabilities decrease with the GMA content increases.5. A series of films were prepared in different curing temperatures. Effects of GMA contents, curing agents and curing temperatures to the mechanical properties, crosslinking and water absorption were studied. The results show that films with high content of GMA and curing temperatures can improve tensile strength, tensile modulus, glass transition temperature (Tg), thermal stability and crosslinking degree, but decrease the water absorption and elongation at break. Aliphatic amine curing agent can increase crosslinking degree. |
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