Modeling the Viscoelastic Response of Suspension of Particles in Polymer Solution: The Effect of Polymer‐Particle Interactions (original) (raw)
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Polymer Bulletin, 2009
We investigate the relation between structure and viscoelasticity of model polymer nanocomposite systems based on a mixture of spherical nanoparticles and different polymer matrices. When Brownian motions become relevant, the composites exhibit a strong time dependence of the linear visoelastic moduli, which is indicative of the three-dimensional structuring of the filler in the melt polymer. Despite the complexity of the rheological response, we show that the viscoelasticity of the samples can be rationalized by splitting it into the independent responses of the ''viscous'' suspending polymer melt and that of the ''elastic'' particle network. Besides underlying the similarities between polymer-based nanocomposites and Newtonian colloidal suspensions, our analysis is expected to be useful for understanding the behavior of other complex fluids where the elasticity of the components may be superimposed.
Journal of Polymer Science Part B: Polymer Physics, 2011
The influence of nano-scale particles on the viscoelastic properties of polymer suspensions is investigated. We have developed a simulation technique for the particle orientation and polymer conformation tensors to study various features of the suspensions. The nano-particles are modeled as thin rigid oblate spheroid particles and the polymers as FENE-P type viscoelastic and Newtonian fluid. Both interparticle and polymer-particle interactions have been taken into account in our numerical computations. The nonlinear viscoelastic properties of nanocomposites of layered silicate particles in non-Newtonian fluids are examined at the start-up of shear flow and are interpreted using the model to examine the effects of model parameters as well as flow conditions on particle orientation, viscosity, and first normal stress difference of the suspensions. We have studied the microstructure of polymer-clay nanocomposites using X-ray diffraction (XRD) scattering and transmission electron microscopy (TEM). The rheology of these nanocomposites in step-shear is shown to be fairly well predicted by the model. V C
Microstructure-dependent viscosity in concentrated suspensions of soft spheres
Physical Review E, 1997
Monodisperse colloidal suspensions of polymethylmethacrylate spheres swollen in benzyl alcohol have been rheologically examined under applied steady and oscillatory shear while simultaneously monitoring microstructure via light scattering. In concentrated samples, long-lived nonequilibrium microstructures can be induced, corresponding to random hexagonal-close-packed planes ͑hcp͒ stacked in the direction of the shear gradient. The direction of closest packing within each hcp plane can be oriented along either the vorticity or direction of flow. Creep and creep recovery measurements have been examined for each of these two orientations as a function of particle concentration and stress. Results indicate a strain-dependent dissipative process correlated with changes sample microstructure, while dynamic measurements of the storage modulus show no significant difference between microstructures. We argue that instantaneous viscosities can be measured and show how they are correlated with changes in particle microstructure. The observed elastic response in these suspensions will be shown to be due to local microstructure and particle deformation. ͓S1063-651X͑97͒16105-0͔
Viscoelasticity of polymers filled by rigid or soft particles: Theory and experiment
Polymer Composites, 1996
An improved modeling for the viscoelasticity of polymers filled by rigid or soft inclusions is proposed. Such a self-consistent scheme can predict the strong increase in the reinforcement effect of the polymer matrix observed for large volume fractions of fillers. Then, it is based on both (i) the percolation concept and (ii) the definition of an original "representative morphological motif" accounting for local phase inversions due to the presence of clusters of particles. To illustrate the validity of such an approach, the predicted viscoelasticity of polystyrene filled either by glass beads or by rubbery inclusions is compared with experimental data and/or theoretical results that issue from other modelings.
Model for the Shear Viscosity of Suspensions of Star Polymers and Other Soft Particles
Macromolecular Chemistry and Physics
We propose a model to describe the concentration dependence of the viscosity of soft particles. We incorporate in a very simple way the softness of the particles into expressions originally developed for rigid spheres. This is done by introducing a concentration-dependent critical packing, which is the packing at which the suspension looses fluidity. The resultant expression reproduces with high accuracy the experimental results for suspensions of star polymers in good solvents. The model allows to explain a weak increase of the viscosity observed in the case of diblock copolymer stars suggesting that the reason for this peculiar behavior is mainly a consequence of the softness of the particles. In the semi-dilute regime, suspensions of star polymers are modeled using the Daoud-Cotton picture to complete the description in the whole concentration regime.
Viscosity behaviour of particles with non-adsorbing polymers
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004
A series of well characterised cis-poly(isoprene) (PIP) polymers (M w = 1180, 8000, 28 300, 31 500, 86 000, 115 000 and 130 000) have been added to dispersions of poly(12-hydroxystearic acid) (PHS) coated poly(methylmethacrylate) (PMMA) particles in dodecane. The ratio of particle size to adsorbed layer was also varied. For a given added polymer molecular weight, the polymer concentration in the continuous phase covered the dilute, semi-dilute and concentrated regimes as defined by the critical concentrations c * and c * * . The viscosity behaviour of latex dispersions with added polymer were similar for all latex/polymer combinations except when polymer M w = 1180 was added. In the latter case, the effect of adding polymer reduced both the viscosity and shear thinning behaviour. This supports the contention that the lower molecular weight polymer acts more like a diluent than a depletent. The behaviour of the viscosity ratio (the viscosity of the dispersion relative to that of the medium) as a function of polymer concentration increased with an increase in the polymer concentration until some critical concentration (c max ) for all polymers except for a polymer molecular weight 1180 Daltons. The addition of the polymer M w = 8000 gave the highest viscosity ratio values in the polymer concentration range studied. It was found that the viscosity of all latex/polymer combinations decreased with an increase in temperature. The results suggest that the viscosity behaviour cannot be explained on the basis of a simple steric-elastic model and require a modified theoretical treatment.
Effect of Nanoscale Fillers on the Viscoelasticity of Polymer Nanocomposites
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012
For viscoelastic materials the stiffness and loss properties directly depend on not only strain but also strain rate and implicitly depend on temperature via time temperature superposition, which in case of harmonic loading leads to frequency dependent response. For viscoelastic composites in which at least one of the constituent materials is viscoelastic, there is great utility in the ability to predict the effective dynamic mechanical properties as a function of the constituent phase properties and geometry. The presence of different concentrations of nanofillers not only directly impacts the nanocomposite effective properties, but also contributes to the formation of an interphase layer, which also has a very strong influence on the effective properties. The interphase layer usually has properties which are distinct from that of the particle and the matrix phases. In this paper micromechanical methods combined with the correspondence principle of viscoelasticity are used to obtain the effective damping properties of viscoelastic composites. The interphase layer is modeled using the composite cylinder model and the composite sphere model and its effect on the overall stiffness and damping of the composite is investigated.