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Aqueous core–shell latexes were synthesized through two-step emulsion copolymerization of vinylidene chloride (VDC) with ethyl acrylate (EA) and butyl acrylate (BA), respectively. First, seed latexes of EA-VDC85 copolymers with 85% VDC content were prepared by the binary emulsion copolymerization of VDC with EA. Subsequently, EA-VDC85 seed latexes were employed in the seed emulsion copolymerization of VDC with BA and the resulting BA-VDC80 copolymers with 80% VDC content covered onto EA-VDC85 seed latexes to form the core–shell latexes. Transmission electron microscopy and dynamic light scattering characterization demonstrated that the size and size uniformity of seed latexes were influenced markedly by the content of emulsifiers in the copolymerization, and higher emulsifier content led to smaller and more uniform latexes. Furthermore, only the utilization of homogeneous seed latexes in the seed emulsion polymerization could lead the majority of the formed latexes to bear the core–shell structure. These ...

Aqueous latexes of copolymers of vinylidene chloride (VDC) with an acrylate, namely, methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), or 2-ethylhexyl acrylate (EHA), were employed to form a double-layer coating film for the heavy-duty anticorrosion of metal. Measurements of the water-vapor transmission rate and oxygen-gas transmission rate and electrochemical impedance spectroscopy (EIS) demonstrated that the barrier properties of MA–VDC and EA–VDC films were better than those of BA–VDC and EHA–VDC films. Among the MA–VDC and EA–VDC coatings, EA–VDC85 showed better comprehensive properties and, thus, was selected as the top layer of the designed double-layer coating film. Adhesion tests demonstrated that the BA–VDC and EA–VDC coatings had better adhesion to tinplates than the MA–VDC and EA–VDC coatings and, thus, were suitable for use as the bottom layer of the designed double-layer coating film. The characterizations of the double-layer coating films by adhesion tests and EIS showed that BA–VDC75 was the optimal bottom layer. Under harsh salt-spray corrosion conditions, the optimal double-layer coating film (ca. 50-μm thickness) with EA–VDC85 as the top layer and BA–VDC75 as the bottom layer could protect tinplate well for at least 800 h, and the adhesion of the coating film to the tinplate was still excellent even after 1000 h of corrosion. Scanning electron microscopy, differential scanning calorimetry, and Fourier-transform infrared spectroscopy were used to evaluate the corroded double-layer coating films.