Green synthesis and properties of an epoxy-modified oxidized starch-grafted styrene-acrylate emulsion

An epoxy-modified oxidized starch-grafted styrene-acrylate (E-g-OS-P (BA-St)) emulsion was synthesized via soap-free core-shell emulsion polymerization without adding any solvent that could cause environmental problems. The emulsion exhibited excellent stability, chemical properties and mechanical performance. The synthesized emulsion was characterized by Fourier transform infrared spectroscopy (FTIR) and C-13 NMR spectroscopy. Transmission electron microscopy (TEM) suggested that the OS-P (BA-St) latexes had certain umbrella structures and that the epoxy resin cross-linked a plurality of umbrella structures. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the thermal stability and glass transition temperature (Tg) of the polymer became higher as the content of epoxy resin increased. Atomic force microscopy (AFM) was utilized to characterize the surface morphology of the films. The film with 10% epoxy resin (based on the mass of monomers) possessed superior tensile strength and elongation, exhibiting a nearly 100% increase in tensile strength relative to that of neat latexes without epoxy. Additionally, the mechanism of polymerization and film formation of the E-g-OS-P (BA-St) emulsion were analysed.