Rheology of EVA Layered Silicate Nanocomposites
Vanja Pasanovic-Zujo, Rahul Gupta, Sati N. Bhattacharya
RMIT University
Australia

Keywords: Exfoliation, Rheology, EVA


Rheological properties of a series of copolymer of ethylene-co-vinyl acetate (EVA) and organo-silicate by melt intercalation were studied to develop a fundamental understanding of the relationship between rheology and the structure of nanocomposites. The microstructure of the EVA-nanocomposites was examined by X-ray diffraction analysis and environmental scanning electron microscopy.
The steady shear rheological behavior of molten EVA-nanocomposites was studied. The measurements of the shear properties of the EVA-nanocomposites were performed on the Advanced Rheological Expansion System (ARES). The shear viscosities for these nanocomposites exhibit enhanced shear-thinning at all shear rates, with the viscosity at high shear rates being almost same to the unfilled polymer. Furthermore, the elasticity was examined by the first normal stress difference and was highly dependent on the silicate loading. Both storage and loss moduli increased with silicate loading at all frequencies and showed solid-like behavior at low frequencies due to formation of a percolation network structure.
Uniaxial viscosities of the EVA-nanocomposites were also studied using Rheometrics Extensional Rheometer (RME). In these nanocomposites, the presence of the organo-silicates reduced the strain hardening under uniaxial extensional flow.