On the rheology of filled polymers

Leonov, A. I.

doi:10.1122/1.550109

Cited by 115 publications

(85 citation statements)

References 23 publications

(48 reference statements)

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“…If the polymer melt is filled with attractively interacting nanoparticles, its rheological behaviour can be relatively well described in the framework of superposition approach originally proposed by Leonov [17]. In this approach the total stress tensor, σ σ, is represented by a sum of two stresses, as shown by Equation (2): (2) where σ σ p is the viscoelastic stress arising in the matrix due to orientation of polymer strands.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The second component on the right side of Equation (2), σ σ f Net , arises due to attractive interactions between the particles. It is described by a modified viscoelastic Maxwell model containing a structural parameter that reflects the state of the particle network at particular shear conditions [17]. Thus, we consider only hydrodynamic interactions between CNTs and the polymer matrix and neglect possible attractive interactions between them.…”

Section: Model Descriptionmentioning

confidence: 99%

“…This is hardly the case as the loss modulus of highly filled polymer nanocomposites considerably exceeds that of a polymer matrix at small and intermediate frequencies and even exhibits a kind of low-frequency plateau as can be seen from Figure 5b. To describe a non-vanishing G″ f at small frequencies, one should add to the left side of Equation (13) the residual parameter α [17], see Equation (14): (14) This expression for mobility function will be used in the modeling of stress growth curves as well as of time-dependent viscoelastic moduli in the flocculation experiment. To calculate the latter let us consider the oscillatory shearing described by Equation (15): (15) The changes in the structural parameter ξ b (t) can be calculated using Equations (10) and (11) in which instead of γ .…”

Section: Modified Viscoelastic Maxwell Modelmentioning

confidence: 99%

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Experimental and theoretical studies of agglomeration effects in multi-walled carbon nanotube-polycarbonate melts

Richter¹,

Saphiannikova²,

Jehnichen³

et al. 2009

Express Polym. Lett.

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Abstract. In this study we report on morphological and rheological characterization of multi-walled carbon nanotube (MWNT)-polycarbonate composites produced by injection molding. The main focus is to carry out nonlinear viscoelastic experiments that allow following the structural rearrangements of carbon nanotubes in the polycarbonate melt. Small angle X-ray scattering reveals only a slight orientation of MWNTs in the as-received samples, i.e. after application of extremely high shear rates. Thus, the main structural effect observed during the stress growth experiment is the breakage of MWNT agglomerates. To study this effect in detail a flocculation experiment, in which the sample undergoes oscillatory deformation first at a small strain amplitude in the linear regime succeeded by higher amplitudes in the nonlinear regime, has been carried out. The agglomeration process manifests itself in an increase of the storage and loss moduli in the linear regime, whereas the deagglomeration process does vice versa. The corresponding effects can be described in the frame of a superposition approach that takes into account the stress contribution of the polycarbonate matrix, the hydrodynamic reinforcement due to embedded nanotubes and the viscoelastic stress due to the presence of a MWNT-network.

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Section: Model Descriptionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Modified Viscoelastic Maxwell Modelmentioning

confidence: 99%

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Experimental and theoretical studies of agglomeration effects in multi-walled carbon nanotube-polycarbonate melts

Richter¹,

Saphiannikova²,

Jehnichen³

et al. 2009

Express Polym. Lett.

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“…Ë l'heure actuelle, peu d'Žtudes ont ŽtŽ (Coussot et al, 1993) qui tient compte des effets du seuil et de la thixotropie pour les dispersions de particules interactives. Ce mod•le est b‰ti sur des considŽrations provenant de la thermodynamique des syst•mes hors Žquilibre (Leonov, 1990 (Loeber, 1992). La taille des feuillets est de l'ordre de 1 ˆ 2 mm.…”

Section: Introductionunclassified

“…Des essais fiables d'une durŽe de l'ordre de 24 heures ont pu ainsi •tre rŽalisŽs. Par ailleurs, l'utilisation de surfaces rugueuses a permis de s'affranchir du probl•me de glissement (Magnin et Piau, 1987et 1990. Des essais en rŽgime permanent, dynamique et transitoire ont ŽtŽ effectuŽs.…”

Section: Introductionunclassified

Caractérisation rhéologique et modélisation structurelle des systèmes argile-polymère. Application aux fluides de forage

Cartalos

Baylocq

Lecourtier

et al. 1997

Rev. Inst. Fr. Pét.

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Le comportement rhŽologique des syst•mes argile-polym•re couramment utilisŽs dans les formulations des fluides de forage est examinŽ dans cet aricle. Un protocole d'essai adaptŽ ˆ leur nature thixotrope qui permet d'effectuer des mesures reproductibles est mis au point. Les propriŽtŽs intrins•ques du matŽriau sont ainsi dŽterminŽes sur toute la gamme de sollicitations : du comportement solide aux faibles dŽformations au comportement fluide aux taux de dŽformations intenses.Il est montrŽ que ces syst•mes sont caractŽrisŽs par des temps de restructuration longs, par des rhŽogrammes en rŽgime permanent prŽsentant un minimum de contrainte et par des dŽpassements importants de la contrainte lors des essais transitoires. Ces effets peuvent •tre compl•tement masquŽs par des procŽdures d'essai prŽconisŽs par les normes en vigueur dans le forage.Une loi de comportement structurelle rŽcente qui relie les propriŽ-tŽs thixotropes et viscoŽlastiques du matŽriau aux mŽcanismes de crŽation et de rupture des flocs peut reproduire l'ensemble des phŽnom•nes observŽs. Sa capacitŽ de dŽcrire le changement de structure au sein du fluide sous Žcoulement ou au repos et les variations associŽes de la contrainte permet d'envisager une meilleure modŽlisation de l'hydraulique du forage. RHEOMETRY AND STRUCTURAL MODELLING OF CLAY-POLYMER SYSTEMSThe rheological behaviour of clay-polymer systems that are currently used in the formulation of drilling fluids was studied. A specific experimental procedure was used to account for thixotropic effects and obtain, thus, reproducible results. In this way it was possible to determine intrinsic properties in the whole range, from solid behaviour below the yield stress to liquid behaviour at very high shear.These systems are shown to be characterised by very long time scales of structure recovery, by the existence of a minimum shear stress in the steady state flow curve and by important stress overshoots in transient flows. These effects can be completely masked, if standard testing procedures like the ones specified by the norms of the drilling industry are used.A recent structural constitutive equation that related thixotropic and viscoelastic properties to the formation and break-up of flocs was Se examina en el presente art'culo el comportamiento reol-gico de los sistemas arcilla-pol'mero que se utilizan corrientemente en las formulaciones de los fluidos de perforaci-n. Se ha desarrollado un protocolo de ensayo adaptado a su naturaleza isotr-pica que permite efectuar mediciones reproducibles. De este modo se determinan las propiedades intr'nsecas del material en la totalidad de la gama de solicitaciones : desde el una comportamiento s-lido con deformaciones reducidas hasta el comportamiento fluido con relaciones de deformaci-n intensas.Se demuestra que estos sistemas se caracterizan por largos tiempos de reestructuraci-n, por programas en rŽgimen permanente que presentan tensiones m'nimas y por superaciones importantes de la tensi-n en ensayos transitorios. Estos efectos pueden verse ocultados por ...

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