Rheology of silica-filled polystyrene: From microcomposites to nanocomposites

Abstract

Rheology and viscoelastic behavior of polystyrene (PS)/silica microcomposites and nanocom posites were studied. The apparent viscosity, transient shear stress growth after startup shear flow and stress relaxation after cessation of flow at various shear rates, the complex dynamic viscosity, the storage and loss moduli at small and large strain amplitudes and various frequencies were performed. The effect of size, shape and volume concentration of silica was discussed. The maximum volume concentration, corresponding to the concentration at which the relative viscosity of mixtures goes to infinity, with respect to the hydrodynamic contribution of the particles and to polymer-filler interactions was obtained. The difference between the yield stress and residual stress is shown. The domain of equivalence between the apparent viscosity as a func tion of the shear rate in steady state flow and the complex dynamic viscosity as a function of the strain rate amplitude in highly nonlinear region of oscillatory flow was established. The viscoelastic behavior was inter preted based on the morphology of microcomposites and nanocomposites observed by SEM.

Rheological Behaviour of Highly Filled Materials for Injection Moulding and Additive Manufacturing: Effect of Particle Material and Loading

“…This indicates that the behaviour of the composites at high frequencies was dominated by the binder system (matrix) and that the contribution of filler particles was less significant. Similar findings were reported for different highly filled composites; for example, SBR rubber and carbon-black and silica particles [44], polydimethylsiloxane (PDMS) and spherical glass beads [49], polyethylene terephthalate (PET) and ferrite nanoparticles [50], and PP and ceramic powder [51]. In the low-frequency region (below ≈10 rad/s) the flattening of the G curve and to a lesser extent also G" curve could be observed.…”

“…This indicates that the behaviour of the composites at high frequencies was dominated by the binder system (matrix) and that the contribution of filler particles was less significant. Similar findings were reported for different highly filled composites; for example, SBR rubber and carbon-black and silica particles [44], polydimethylsiloxane (PDMS) and spherical glass beads [49], polyethylene The comparison of the frequency behaviour of composite materials at different loading levels (Figure 6) revealed that, as in the case of amplitude sweep tests, the viscoelastic behaviour in LVR depends on the type of filler material. However, in the case of 30 vol.% filler loading, there was no difference between dynamic behaviour (G and G") of Al and 316L material, respectively, in the whole frequency range studied.…”

“…The flattening of the curve corresponds to frequency-independent behaviour and indicates that the particle-particle interactions become dominant at lower frequencies [21,24,52]. Frequency independent behaviour of filled composites has also been observed for different fillers and binder combinations [40,44,[49][50][51]53]. It can be seen from Figure 6 that all materials exhibited frequency-dependent behaviour of the moduli.…”

Polymer Grafted Nanoparticle Viscosity Modifiers

“…Additionally, for higher particle concentrations, the viscosity can be predicted via the empirical Krieger–Dougherty equation where [η] is the intrinsic viscosity and φ m is the maximum loading. This equation has been used to fit experimental data for concentrated colloidal suspensions and composites with micron sized fillers . Both models predict an increase in viscosity with increasing filler loading.…”

Roll-to-plate fabrication of microfluidic devices with rheology-modified thiol-ene resins

“…In suspensions, size, size distribution, shape and volume fraction of the filler particles affect the flow properties [25]. Fumed silica is a widely used filler with particle sizes ranging from 5 to 50 nm [26,27] and it has been applied to modify, for example, the flow properties of polymers such as PDMS [28,29], PS [30], polyethyleneoxide (PEO) [31], polyethyleneglycol (PEG) [32], and polyethyleneterephtalate (PET) [33], as well as UV curable systems including carbodiimide diacrylate [34] and TE [35]. Due to their large surface area-to-weight ratio, nanoparticles can alter material properties at significantly smaller weight fractions than their micro-sized counterparts [30,31,36].…”