Melt rheology of organoclay and fumed silica nanocomposites

Abstract

The objective of the present work is to investigate, from the open literature, the recent developments in the rheology of silica and organoclay nanocomposites. In particular, this paper focuses on general trends of the linear viscoelastic behaviour of such nanocomposites. Hence, the variations of the equilibrium shear modulus and critical strain (limit of linearity), which depend on power laws of the volume fraction of particles, are discussed as filler fractal structure. In the third section, the strong nonlinearity behaviour (Payne effect) of filled polymers has been discussed in terms of filler nature. Typically two mechanisms arise to depict the linear solid-like behaviour and the Payne effect: particleeparticle interactions is the dominant mechanism in fumed silica nanocomposites whereas particleepolymer interaction is the dominant one in colloidal silica nanocomposites at identical filler concentrations. However, these interactions are balanced in each nanocomposite systems by the silica surface treatments (chain grafting, silane modification) and the molecular weight of the matrix. Finally, we aim to unify the main findings of the literature on this subject, at least from a qualitative point of view.We finally report on the thixotropy and modulus recovery after a large deformation in steady and dynamic shear conditions. Following this, the nonlinear rheological properties of nanocomposite materials have been discussed. The discussion is particularly focused on the effect of flow history (transient shear experiments) on the orientationedisorientation of clay platelets. Actually, the linear and nonlinear rheological properties are consistent with a network structure of a weakly agglomerated tactoids. As far as exfoliated clay nanocomposites are concerned, the interparticle interaction is the dominant effect in the nonlinearity effect.

Morphological Study of HDPE/Clay Hybrids Synthesized by an Alternative Compatibilization Path

“…Chen et al, 2005; TA Instruments, (RN-9B)). Unlike other works describing an increase in viscosity due to the addition of filler into the polymeric matrix (Cassagnau, 2008), the materials modified with clays showed lower values than that corresponding to HDPE. In the case of PE-sC and PE-oC, one of the factors that c o u l d g i v e r i s e t o t h i s b e h a v i o r w o u l d b e the diminution among PE macromolecules interactions due to the presence of clay tactoids.…”

“…Particularly, the structural characterization of filled polymer through low-amplitude oscillatory experiments allows determining the linear viscoelastic properties that describe the material behavior in a condition where the structure remains practically unchanged. These properties are sensitive to the interactions that take place among phases, and to the degree of miscibility reached (Okamoto, 2005;Bretas & D'Avila, 2000;Cassagnau, 2008), due to the fact that the applied strain deformations are small enough to affect the material properties.…”

Efficient one-step melt-compounding of copolyetheramide/pristine clay nanocomposites using water-injection as intercalating/exfoliating aid

“…Rheology is one of the easiest and best way to quantify the filler dispersion into polymer nanocomposites, loaded with carbon nanotubes [55,56] or with clay platelets [57]. Effects are more noticeable on the storage modulus (G%) than on the loss modulus.…”

Investigations on cycle time reduction, dynamic mechanical properties and creep for rotationally moldable nano composites of linear low density polyethylene and fumed silica

“…The improvements in mechanical properties, such as tensile strength, impact toughness, creep, stress relaxation, etc. were reported with addition of nano fillers like, organo clays [4], metal nanoparticles [5], titanium oxide [6], zinc oxide [7], calcium carbonate [8] and silica nanoparticles in a polymer matrix [9]. Along with the improvements in mechanical properties, cycle time reduction for the molding process is also highly desired.…”