Preparation And Characterization Of Core-Shell Structured Epoxy-Acrylate Emulsion

In recent years,as the increase of the people's environment awareness,much attention has been paid on the water-based coatings with low volatile organic compounds,core-shell epoxy-acrylate emulsions have the advantages of both epoxy resin and acrylic resin,the film prepared from it has the property of self-stratification.In this article,the epoxy emulsion was first prepared by the phase inversion technique,Span-80 and SDS were used as the composite emulsifiers,and epoxy E-51 was used as the matrix resin.The optimal emulsion was obtained when the mass ratio of Span-80 and SDS was 2:1,the amount of the mixed emulsifiers was 10 wt%.the emulsification temperature was 50? and the stirring speed was 1000 r·min-1.Then the three-layer core-shell emulsion was synthesized using the epoxy emulsion as the core by semi-continuous emulsion polymerization.The styrene-acrylate emulsion was synthesized by semi-continuous emulsion polymerization.Hydroxyethyl acrylate(HEA)was used as a functional monomer instead of acrylic monomers to provide reactive group.This substitution avoided the addition of volatile organic solvent to neutralize the carboxyl group.Sodium dodecyl sulfate(SDS)and sorbitan monooleate(Span-80)(the mass ratio of SDS and Span-80 was 1:2)were used as composite emulsifiers.Butyl acrylate(BA),styrene(St),methyl methacrylate(MMA)and hydroxyethyl acrylate(HEA)were served as the monomers,The emulsion with uniform particle size distribution,good stability and heat resistance can be prepared when the amount of the epoxy resin is 30 wt%,the amount of initiator is 0.8 wt%,the temperature is 80?,the polymerization time is 6 h.The particle size and morphology were characterized by FT-IR and TEM,the surface properties of the film were characterized by SEM and AFM,the stability of the film was synthesized by TGA.The results showed that:The emulsion was with clear three-layer core-shell structures and uniform particle size distribution,the core was prepared as epoxy emulsion employing phase inversion with the particle size of 140nm,the inner shell was formed by the aggregation of epoxy resin and the polyacrylate at the stage of seeded polymerization with the particle size of 180 nm,and the outer shell was formed at the grow-stage polymerization of acrylate monomers with the particle size of 220 nm,and the corresponding film prepared by the emulsion had the characteristic of self-stratification.The thermal stability of epoxy-acrylate emulsion was in between compared to TG curves of epoxy emulsion and acrylate emulsion,and was reduced with the increase of the epoxy content.The AFM data indicated that the planarity of the film prepared by three-layer core-shell structured epoxy-acrylate emulsion with 30 wt%epoxy content was good than that of the film prepared by epoxy emulsion,which could present better stain resistance property.