Shear response of layered silicate nanocomposites

Abstract

The linear and nonlinear melt state viscoelastic properties for a series of layered silicate based intercalated polymer nanocomposites are studied to elucidate the role of highly anisotropic nanometer thick layers in altering the flow properties of such hybrids. The steady shear viscosities for the nanocomposites exhibit enhanced shear-thinning at all shear rates, with the viscosity at high shear rates being almost independent of silicate loading and comparable to that of the unfilled polymer. Further, the elasticity, as measured by the first normal stress difference, when compared at constant shear stress is surprisingly independent of the silicate loading and identical to that of the unfilled polymer. This unique combination of unfilled polymerlike viscosity and elasticity for these filled nanocomposites, is attributed to the ability of the highly-anisotropic layered silicates to be oriented in the flow direction and results in a minimal contribution by the silicate layers to both the viscosity and the elasticity of the hybrids.

Strain amplitude response and the microstructure of PA/clay nanocomposites

“…[8,9]. Higher viscosities and shear thinning properties can be observed for nanocomposites at relatively low shear rate at which the matrix exhibits a Newtonian response, but when the shear rate increases, the viscosities of nanocomposites decrease significantly [10]. The results can be attributed to the presence of anisotropic nanoclays forming a network structure, which can be broken down under large shear deformation.…”

“…The critical loading of PA10 for the percolation is only 0.75%. Previous studies suggested that the anisotropic nanoclays could be aligned to the flow direction under strain amplitude and rupture clay particle-particle interaction [10]. Interestingly, Figure 4 shows that the logarithm of the critical strain amplitude decreases linearly with clay loading.…”

Layered silicate polymer nanocomposites: new approach or illusion for fire retardancy? Investigations of the potentials and the tasks using a model system

“…It should be noted that the quantitative characterization of delamination and exfoliation for good nanocomposites is a general problem for layered silicate polymer nanocomposites, and only a few very recent sources have reported promising approaches to tackling this problem, for instance using NMR techniques. 20,21 In this study, a pragmatic approach using rheology 22,23 was performed to characterize the morphology of nanocomposite structures. The investigated nanocomposites are based on similar compounds, so that the difference in shear viscosity is correlated to the degree of exfoliation of the silicate layers.…”

Rheological properties of asphalt/SBS/clay blends

“…Lee et al showed that an organically modified montmorillonite leads to a change in the microphase separation behaviour of styrene-(ethylene-co-butylene)-styrene triblock copolymers (SEBS), thus also influencing the order-disorder transitions [28]. Analogously, the influence of the addition of small quantities of anisotropic layered silicates on the ordering of block copolymers was studied by Krishnamoorti et al [29] and Silva et al [30][31][32]. The effect of the preparation technique was investigated by Yamaguchi and Yamada [33], Chang et al [34], Carastan and Demarquette [35].…”