Polylactide layered silicate nanocomposites with enhanced extensional rheological properties

Commercial linear polylactic acid (PLA) grades do not offer the processability needed for some polymer processing operations involving extensional flow, owing to their low melt strength and absent or weak strain hardening behavior. The presence of organoclays in polymeric matrices can significantly affect their melt rheological behavior, both in shear and extensional flow, as a function of the nanoscale structure and polymer-clay interfacial characteristics. In particular, in this work nanocomposites were produced by melt compounding using a semi-crystalline polylactide grade (PLA 4032D) and two different organo-silicates (Cloisite 30B and Nanofil SE3010). The morphological characterization in solid and molten state, realized by TEM and dynamic rheological measurements, pointed out the influence of composition on the nanostructure of the hybrids. The elongational flow characterization of the materials evidenced for NSE3010 based hybrids a marked extensional thickening, while the stronger polymer–silicate interactions and the better clay dispersion, observed in presence of C30B, determine increments in viscosity