Linear viscoelasticity, extensional viscosity, and oxygen permeability of nanocomposites based on propylene copolymer and organoclay

Abstract

Random propylene-terpolymer (PEBC)/organophilic montmorillonite nanocomposites were prepared by melt mixing, using PEBC modified with maleic anhydride (PEBCg) as compatibilizer. Clay concentrations up to 8 wt %, compatibilizer/clay ratios up to 3:1 and concentrations of anhydride groups (AG) in PEBCg of 0.4 and 0.6 wt % were considered. The degree of exfoliation of the clay increases with PEBCg content and its concentration of AGs. The dynamic moduli allow estimating the percolation threshold of the nanofiller at 5.4 wt %, which yields an average of 11 silicate layers per tactoid at percolation, in agreement with the minimum thickness estimated from XRD data. The presence of exfoliated clay gives place to strain hardening and softening, depending on clay concentration and magnitude of the Hencky strain. The amount of exfoliated clay, however, plays a minor role in front of the content of AGs of the compatibilizer in regard with the oxygen permeability of the polymer.