Investigating the effects of crosslinker systems on the properties of waterborne epoxy-acrylate core-shell emulsion, film, and coating

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Recently, waterborne coating has been a trend in research. The waterborne epoxy-acrylate (WEA) core-shell emulsion has been widely studied. Hence, in this research, we have investigated the impacts of the crosslinking systems on the properties of the WEA core-shell emulsion, film and coatings. The emulsions were synthesized through semi-continuous emulsion polymerization. Two kinds of crosslinking systems were achieved by adding the crosslinker (MAA) at the core layer (intralayer crosslinking) or the shell layer (interlayer crosslinking). The interlayer crosslinking provides a very high crosslinking density (7.01 × 10-4 mol cm-3) as it involves the crosslinking of polymer chains between the core and shell layers. Consequently, this film has a compact structure and high modulus (489.12 MPa) but low elongation at break (3.20 %). Conversely, the intralayer crosslinking has a low crosslinking density (1.59 × 10-4 mol cm-3). Hence, the film has a loose structure and low modulus (0.38 MPa) but high elongation at break (225.29 %). This is because it only involves crosslinking with the polymer chains in the same layer, leading to poor compatibility between the layers. The incorporation of crosslinker also allows two Tg to be observable. Lastly, the crosslinking system does not affect the stability (shelf-life) of the emulsion, but the oxirane ring of the Epoxy (EP) does. We believe the findings from this research could help future researchers better understand the properties of WEA core-shell coating.

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