Melt viscoelasticity of polyamide 6/organoclay nanocomposites

Commercial nanocomposites of polyamide 6, prepared by melt compounding with organoclay hybrids, were characterized by complex viscosities and relaxation time spectra derived from storage and loss shear moduli measured in the melt state at 230degreesC in the frequency window spanning about three decades. The results were rationalized in terms of the following model considerations. The decrease of similar to25% (compared to the pristine sample) in Newtonian viscosity at the lowest clay loading (2.5%) suggested a lower equilibrium elasticity modulus of an entangled melt, as if the small amounts of organoclay nanoparticles acted as specific "diluents" for the initial entanglement network. However, at increasing clay contents this effect was apparently taken over by the ever growing importance of strong interactions at the nanoparticle/melt interface, leading to the formation of a fairly thick boundary interphase (BI) around the nanoparticles and, eventually, ending up in the build-up of an "infinite cluster" of clay nanoparticles coated with BI at the highest (albeit still unusually low) clay loading (7.5%).