Abstract
In order to develop a waterborne epoxy-styrene–acrylate composite latex with a better stability and anticorrosion resistance, a novel synthetic approach has been proposed. First, modified by methyl acrylic, epoxy resin containing terminal C=C double bonds was successfully synthesized, where epoxide groups were partially retained. Then, by structural design and multi-stage seed emulsion copolymerization, a stable waterborne epoxy-styrene-acrylate composite latex composed of a modified epoxy resin acrylate polymer as the core, inert polystyrene ester as the intermediate layer, and carboxyl acrylate polymer as the shell was successfully fabricated. The structure of the obtained latex was characterized by fourier transform infrared (FTIR) and transmission electron microscopy (TEM). The stability of the composite latex was tested based on the wet gel weight, Zeta potential, and storage stability, and the corrosion resistance of the composite latex films was analyzed by electrochemical measurements and salt spray tests. The thickness of each layer of the composite latex was calculated by the temperature random multi-frequency modulation DSC (TOPEM-DSC) technique. In addition to the successful emulsion copolymerization that occurred between the modified epoxy resin and acrylate monomer, the presence of carboxyl groups in the obtained latex was evidenced, while the epoxide groups were partially retained. The anticorrosion resistance and stability of the multilayer composite latex with the intermediate layer are better than that of the conventional core-shell latex. The outstanding stability and corrosion resistance is attributed to the multilayer core-shell structure. The TOPEM-DSC approach can accurately determine the thickness of the intermediate layer in the multilayer core-shell particles and is a new strategy for characterizing the core-shell structure of polymer particles with a similar monomer composition.
Highlights
With the strict enforcement of laws and regulations for environmental protection, waterborne epoxy resin coatings have attracted much attention
The novelty is to prepare the composite latex by structural design in order to achieve stability and the self-crosslinking of waterborne epoxy resin simultaneously, in which, an inert intermediate layer of the styrene-acrylate copolymer is set between the inner core and outer shell
Depicted in Figure 5with are the transmission electron microscopy (TEM) micrographs of waterborne epoxy‐styrene‐acrylate composites unmodified epoxy resin, as well as those of the conventional core-shell composites with unmodified epoxy resin, as well as those of the conventional core‐shell and three-layer core-shell structure with epoxy resin modified with acrylic acid
Summary
With the strict enforcement of laws and regulations for environmental protection, waterborne epoxy resin coatings have attracted much attention. With the development and application of particle design theory, the preparation of latex particles with a multilayer structure has become a research hotspot [17,18,19,20] This type of polymer can be produced by multistage emulsion polymerization, where there is a growth of previously formed seeds upon the addition of monomer(s), avoiding the need to form new particles. A three-layer core-shell-structured waterborne epoxy-styreneacrylate composite was prepared by multi-stage seed emulsion polymerization. The novelty is to prepare the composite latex by structural design in order to achieve stability and the self-crosslinking of waterborne epoxy resin simultaneously, in which, an inert intermediate layer of the styrene-acrylate copolymer is set between the inner core (with the acrylate polymer containing epoxied groups) and outer shell (with the acrylate polymer containing carboxyl groups). The method using the TOPEM-DSC technique to characterize the application of a multilayer core-shell emulsion for the construction of a latex particle structure has been demonstrated
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