Study On The Anticorrosive Properties Of Water-borne Vinylidene Chloride Copolymer Latexes

In this dissertation, a series of aqueous latexes were synthesized by emulsioncopolymerization of vinylidene chloride (VDC) with acrylates or methacrylates. Theinfluence of the type of the monomer, monomer ratio and the inorganic filler and thecoating process were studied. The details were as follows:1. A series of aqueous latexes with solid contents of56%were synthesized bybinary emulsion copolymerization of VDC with acrylates or methacrylates. TheVDC-methacrylates copolymers performed poor anticorrosive property. The adhesionof VDC-acrylates copolymers increased with the side chain of acrylates increasing.But the barrier performance of the copolymers decreased. The barrier performanceincreased with VDC content increasing, but the adhesion decreased.(VDC/butylacrylate) copolymer with VDC content of80%retained both excellent adhesion tometal and excellent barrier performance. Further study demonstrated that thecopolymer could protect steel from rusting for at least250h under harsh salt-spraycorrosion. The impedance value of the copolymer can maintain1.7×107ohm after250h corrosion.2. The ternary copolymers were synthesized by emulsion copolymerization ofVDC and two kinds of acrylates with different length of side chains. After beingcorroded, the copolymer with VDC content of75%, EHA content of10.85%and MAcontent of10.85%, showed the best anticorrosive performance. The impedance valueof the copolymer can maintain7.4×106ohm after400h corrosion.3. A double-layer coating film was prepared by two kinds of VDC/acrylatecopolymer. Under harsh salt-spray corrosion conditions, the optimal double-layercoating with (VDC/ethyl acrylate) copolymer with VDC content of85%as the toplayer and (VDC/butyl acrylate) copolymer with VDC content of75%as the bottomlayer could protect tinplate well for at least800h. The ratio of the thickness of the toplayer to the bottom layer is2:1. The impedance value of the double-layer coating filmcan maintain6.3×106ohm after800h corrosion.4. Twice-painting technique was adopted to prepare heavy-duty anticorrosivecoating films formed by aqueous latexes of VDC-acrylates copolymers. The acidiclatex solution was adjusted to pH5-6for the bottom painting, whereas it was utilized directly for the top painting.(VDC/methyl acrylate) copolymer with VDC content of85%showed the best anticorrosive performance. After800h it can maintain goodadhesion to steel and the impedance value is2.5×107ohm.5. The influence of anticorrosive property for the added of SiO2showed that theadhesion can be improved if0.5%content of40nmSiO2was added into the(VDC/ethyl acrylate) copolymer with VDC content of80%. After400h corrosion, theadhesion can be still very strong and the impedance value can maintain2.4×107ohm.6. The pilot test was carried out and50kg PVDC latex was synthesized in the100L reactor. The latex was used to prepare container coatings and was evaluatedaccording to the standard of IICL. The result showed that the coating can meet thecorrosion protective requirements.