Fourier Transform Rheology Research Articles

Fourier-transform rheology of unvulcanized styrene butadiene rubber filled with increasingly silanized silica

ABSTRACTSilica as one the most important fillers for rubber material is routinely modified by silane to improve its compatibility with the rubber matrix. Silanization of the silica particle affects both the linear and nonlinear rheological behaviors of the compounds. Their rheological nonlinearity, however, is mostly analyzed in an indirect way from linear rheological parameters, e.g. G′(ω1, γ0) and G″(ω1, γ0), which lose their physical meaning in the nonlinear viscoelastic regime. In the present work, the nonlinearity is directly quantified by the Fourier-transform rheology (FT-Rheology) technique in terms of I3/1(ω1, γ0), the third relative higher harmonic, for unvulcanized styrene butadiene rubber compounds filled with a fixed amount of silica, but varying dosages of silane. With the proposed model for I3/1(γ0), the contributions toward nonlinearity from the filler networks at a low strain amplitude and the one from the polymer networks at high strain amplitude can be successfully separated for filled systems. The utmost nonlinearity contribution from the filler networks decreases with the silane content, which is assigned to the weakening interparticle interaction of the filler. With increasing silanization of silica, the utmost nonlinearity contribution from the polymer networks is found to increase. This nonlinear mechanical response is attributed to the enhanced interfacial interaction between the filler and polymer.

Nonlinear rheological behavior of bitumen under LAOS stress

The linear viscoelasticity and steady shear properties of bitumen are established; however, bitumen used in pavement also supports time-varying loading in the nonlinear regime. Consequently, recent research focuses on the nonlinear rheological behavior of bitumen under time-varying flows that is essential for establishing the constitutive model. Here, we propose a protocol to obtain the nonlinear rheological behavior of bitumen under a large amplitude oscillatory shear (LAOS) stress. The LAOS stress rheological response of both a neat bitumen and a modified bitumen is analyzed by Fourier-transform rheology and strain decomposition to an orthogonal set of Chebyshev polynomials. We find that the relative nonlinearity of bitumen increases with increasing stress and decreasing frequency; the relationship between I3/I1 and stress amplitude can obey the sigmoidal function; the intrinsic nonlinearity Q0 decreases with increasing frequency and decreasing temperature. Both the FT analysis results and decomposition results show that the nonlinearity of modified bitumen B is much more significant than neat bitumen A. Bitumen A exhibits stress softening and stress thinning under all the studied test conditions, but bitumen B exhibits stress stiffening under some conditions.The linear viscoelasticity and steady shear properties of bitumen are established; however, bitumen used in pavement also supports time-varying loading in the nonlinear regime. Consequently, recent research focuses on the nonlinear rheological behavior of bitumen under time-varying flows that is essential for establishing the constitutive model. Here, we propose a protocol to obtain the nonlinear rheological behavior of bitumen under a large amplitude oscillatory shear (LAOS) stress. The LAOS stress rheological response of both a neat bitumen and a modified bitumen is analyzed by Fourier-transform rheology and strain decomposition to an orthogonal set of Chebyshev polynomials. We find that the relative nonlinearity of bitumen increases with increasing stress and decreasing frequency; the relationship between I3/I1 and stress amplitude can obey the sigmoidal function; the intrinsic nonlinearity Q0 decreases with increasing frequency and decreasing temperature. Both the FT analysis results and decomposition...

The Distribution of Nanoclay Particles at the Interface and Their Influence on the Microstructure Development and Rheological Properties of Reactively Processed Biodegradable Polylactide/Poly(butylene succinate) Blend Nanocomposites.

The present work investigates the distribution of nanoclay particles at the interface and their influence on the microstructure development and non-linear rheological properties of reactively processed biodegradable polylactide/poly(butylene succinate) blend nanocomposites. Two types of organoclays, one is more hydrophilic (Cloisite®30B (C30B)) and another one is more hydrophobic (BetsopaTM (BET)), were used at different concentrations. Surface and transmission electron microscopies were respectively used to study the blend morphology evolution and for probing the dispersion and distribution of nanoclay platelets within the blend matrix and at the interface. The results suggested that both organoclays tended to localize at the interface between the blend’s two phases and encapsulate the dispersed poly(butylene succinate) phase, thereby suppressing coalescence. Using small angle X-ray scattering the probability of finding neighboring nanoclay particles in the blend matrix was calculated using the Generalized Indirect Fourier Transformation technique. Fourier Transform-rheology was utilized for quantifying nonlinear rheological responses and for correlating the extent of dispersion as well as the blend morphological evolution, for different organoclay loadings. The rheological responses were in good agreement with the X-ray scattering and electron microscopic results. It was revealed that C30B nanoparticles were more efficient in stabilizing the morphologies by evenly distributing at the interface. Nonlinear coefficient from FT-rheology was found to be more pronounced in case of blends filled with C30B, indicating better dispersion of C30B compare with BET which was in agreement with the SAXS results.

Nonlinear rheology of colloidal suspensions probed by oscillatory shear

The nonlinear stress and microstructural response of a colloidal hard sphere suspension undergoing medium and large amplitude oscillatory simple shear have been studied using Accelerated Stokesian dynamics. The goal is to understand how nonlinearity arises and to link the structural effects to the resulting suspension stress. The imposed shear is given by the time-dependent rate γ̇(t)=γ̇0eiαt. Most results are shown for a hard-sphere suspension at a particle volume fraction ϕ=0.4. These are freely flowing conditions far from either glassy or jammed conditions, but the concept of the particle cage from glass dynamics is used. The cage is defined here in a statistical manner as the surface of elevated nearest neighbor probability, a sphere at contact for equilibrium. The cage concept is used in interpreting the microstructural deformation: For sufficiently small strain amplitude γ0, the cage deforms negligibly due to flow and the suspension remains in the linear response regime, but this is found to require γ0<0.01 at ϕ=0.4, as shown by a spectral decomposition of the microstructure in time, which discriminates rigorously between linear and nonlinear deformation. At larger γ0, termed medium amplitude and large amplitude in other studies, the material response is nonlinear. To preface the large amplitude oscillatory shear analysis, we use linear viscoelasticity theory to compare stress fluctuations at equilibrium to results obtained at finite Péclet number Pe and small γ0, as well as available experimental data and theoretical predictions; Pe=6πηγ̇0a3/kT is the ratio of hydrodynamic to Brownian forces, where η is the viscosity of the suspending liquid, γ̇0 is the shear rate amplitude, a is the particle radius, k is the Boltzmann constant, and T is the absolute temperature. The shear stress σxy and the normal stress differences N1 and N2 are analyzed under oscillatory shear at amplitudes 0.01≤γ0≤3.6 for a range of Pe. (The frequency α is related to Pe through γ̇0=αγ0 and the nondimensional frequency is given by the Deborah number De=Pe/γ0=6πηαa3/kT.) Pipkin diagrams are shown for σxy, N1 and N2. When hydrodynamic forces dominate the flow of the suspension, the complex viscosity |η*| has a nonmonotonic dependence on γ0, and Fourier-transform rheology shows the nonlinearity of the stress response to be maximized at an intermediate strain amplitude that depends on Pe. The elastic and viscous behavior of the suspension, as determined by a Chebyshev polynomial decomposition, is distinctly different for small and large Pe. The influence of the microstructure on the normal stress differences is discussed, noting that N1 is significant only when angular distortion of the microstructure is present, whereas N2 is formed with an accumulation of pair correlation at contact even at low oscillation amplitude.

Analysing the large amplitude oscillatory shear response of a bingham-hooke model in pipkin space and by fourier Transform rheology to predict weak strain overshoots

The work presented in this paper contributes to theory behind the modelling of strain-controlled large amplitude oscillatory shear (LAOS) with weak strain overshoot. The latter term refers to a decreasing strain amplitude dependent storage modulus and a peak in loss modulus. These physical nonlinearities are restricted in this work in order to remain within the geometrically linear theory measured for an inertial system. It is also premised that yielding causes weak strain overshoot. Yielding is modelled with the aid of the Bingham–Hooke model consisting of a Hookean spring connected in series to a Bingham model. In addition, the Bingham–Hooke model is connected in parallel to an rCross model, the LAOS response of which was investigated with the aid of FT rheology in [Boisly et al., Journal of Non-Newtonian Fluid Mechanics 225 (2015) 10–27]. The LAOS behaviour of the Bingham–Hooke model is analysed in this work using Fourier Transform (FT) rheology and Lissajous plots in Pipkin space. This approach facilitates the identification of so-called characteristic points of FT harmonics. These are distinct points – for example maximum loss modulus – easy to determine experimentally and can therefore be used for the purposes of parameter identification. Analytical methods are applied to relate material parameters to characteristic points. It is therefore possible to identify material parameters deterministically without minimising residuals with the aid of nonlinear optimisation algorithms. This insight enables the authors to analytically model nonlinear phenomena based on the characteristic points of FT harmonics. The entire set of elastic, viscous and plastic material parameters – η0, η∞, K1, G, η and yield stress τy – are identified by evaluating the characteristic points of the storage and loss modulus.

Nonlinear rheological behavior of multiblock copolymers under large amplitude oscillatory shear

The nonlinear responses of olefin multiblock copolymers (OBCs) melts were investigated under large amplitude oscillatory shear (LAOS) using Fourier-Transform rheology in this work. Time-temperature superposition (TTS) was examined using linear viscoelastic functions, as well as nonlinear viscoelastic functions like the intrinsic Q factor (Q3,0) and the dynamic moduli of the third harmonic ( G33,0′ and G33,0″). It is found that the intrinsic Q factor (Q3,0) exhibits similar TTS behavior as those of storage moduli and loss moduli. However, the deviation from typical liquidlike behavior of homogeneous melt in Q3,0 is much more evident than that in the storage moduli, indicating more sensitive of Q3,0 to the microstructure than linear viscoelastic functions. In addition, we suggested a new plot, the intrinsic phase angle at third harmonic (δ3,0) versus the intrinsic complex moduli at third harmonic ( |G33,0*|), which is named as the vGP3 plot. Using the vGP3 plot, the much weaker mesophase separation can be d...

Large amplitude oscillatory shear of hard-sphere colloidal dispersions: Brownian dynamics simulation and Fourier-transform rheology

Brownian dynamics simulations of large amplitude oscillatory shear (LAOS) in freely draining, hard-sphere colloidal dispersions are performed. The time varying stress and microstructure under LAOS are measured, and the relationship between microstructural deformation and rheological response is explored. The shear stress, first and second normal stress differences are analyzed by Fourier-transform rheology for dispersions with two volume fractions ϕ=0.10, 0.40. Highly nonlinear microstructural perturbations are identified and correlated with the magnitude of the stress response. The first departures from linearity in the shear and normal stresses are compared to recent theoretical predictions of the same, and agreement with scaling predictions in the limit of high frequency oscillation is found. Higher order nonlinearities in the stress response are found in the regime of rapid oscillation with order unity strain amplitude. These derive from symmetry breaking through shear induced ordering of the dispers...

Two dimensional mechanical correlation analysis on nonlinear oscillatory shear flow of yield stress fluids

Large amplitude oscillation shear (LAOS) is used to investigate the yielding and flow behavior of yield stress materials. Considering the problems in determination of the yield stress from the apparent dynamic moduli and relative harmonic intensity using Fourier Transform Rheology, we proposed a new approach based on 2D mechanical correlation spectra (2D-MCS) to quantify the yield stress. We have proved that the nonlinear synchronous self-correlation intensity as functions of stress/strain amplitude can be used to determine the yield stress unambiguously from the change of scaling exponent. The yield stresses from 2D-MCS analysis are well consistent with those from the stress ramp experiments.

Effects of silica nanoparticles on copper nanowire dispersions in aqueous PVA solutions

In this study, the effects of adding silica nanoparticles to PVA/CuNW suspensions were investigated rheologically, in particular, by small and large amplitude oscillatory shear (SAOS and LAOS) test. Interesting, the SAOS test showed the complex viscosities of CuNW/silica based PVA matrix were smaller than those of PVA/CuNW without silica. These phenomena show that nano-sized silica affects the dispersion of CuNW in aqueous PVA, which suggests small particles can prevent CuNW aggregation. Nonlinearity (third relative intensity ≡ I 3/1) was calculated from LAOS test results using Fourier Transform rheology (FT-rheology) and nonlinear linear viscoelastic ratio (NLR) value was calculated using the nonlinear parameter Q and complex modulus G*. Nonlinearity (I 3/1) results showed more CuNW aggregation in PVA/CuNW without silica than in PVA/CuNW with silica. NLR (= [Q 0(ϕ)/Q 0(0)]/[G*(ϕ)/G*(0)]) results revealed an optimum concentration ratio of silica to CuNW to achieve a well-dispersed state. Degree of dispersion was assessed through the simple optical method. SAOS and LAOS test, and dried film morphologies showed nano-sized silica can improve CuNW dispersion in aqueous PVA solutions.

Rheological characterization of EVA and HDPE polymer modified bitumens under large deformation at 20 °C

Large amplitude oscillatory shear (LAOS) coupled with Fourier transform rheology (FTR) was used for the first time to characterize the large deformation behavior of selected bituminous binders at 20°C. Two polymer modified bitumens (PMB) containing recycled EVA and HDPE and two unmodified bitumens were tested with LAOS-FTR. The LAOS-FTR response of all binders was compared at same frequency, at same Deborah number (by tuning the frequency to the relaxation time of each binder) and at same phase shift angle δ (by tuning the frequency to the one corresponding to δ=50° in the SAOS response of each sample). In all the approaches, LAOS-FTR results allowed to differentiate between all the nonlinear mechanical characteristics of the tested binders. All binders show LAOS-FTR patterns reminiscent from colloidal dispersions and emulsions. EVA PMB was less prone to strain-induced microstructural changes when compared to HDPE PMB which showed larger values of nonlinear FTR parameters for the range of shear strains tested in LAOS.

Characterising skeletal muscle under large strain using eccentric and Fourier Transform-rheology

Characterising the passive anisotropic properties of soft tissues has been largely limited to the linear viscoelastic regime and shear loading is rarely done in the large deformation regime, despite the physiological significance of such properties. This paper demonstrates the use of eccentric rheology, which allows the anisotropy of skeletal muscle to be investigated. The large amplitude oscillatory strain properties of skeletal muscle were also investigated using Fourier Transform-rheology. Histology was used to qualitatively assess the microstructure changes induced by large strain. Results showed that skeletal muscle was strongly anisotropic in the linear regime. The storage and loss moduli were found to be significantly different (p<0.05) between the three fibre alignment groups; for the group tested with fibres perpendicular to plane of shear was 12.3±1.3kPa and 3.0±0.35kPa, parallel to shear direction was 10.6±1.2kPa and 2.4±0.23kPa, and perpendicular to shear direction was 5.5±0.90kPa and 1.3±0.21kPa. The appearance and growth of higher order harmonics at large strain was different in the three testing directions indicating that the anisotropy of muscle affects skeletal muscle behaviour in the nonlinear regime. Histological analysis showed an increasing destruction of extracellular matrix and the rearrangement of fibres with increasing strain indicating mechanical damage at strains of larger than 10%. These microstructural changes could contribute to the complex nonlinear behaviour in skeletal muscle. This paper demonstrates a method of characterising the anisotropic properties in skeletal muscle under large strain whilst giving meaningful information on the physical response of tissue at various strains.

Nonlinearity from FT-rheology for liquid crystal 8CB under large amplitude oscillatory shear (LAOS) flow

This study systematically investigated the nonlinear stress behavior of liquid crystal (8CB, 4-4′-n-octyl-cyanobiphenyl) in lamellar smectic A phase under large amplitude oscillatory shear (LAOS) flow. To investigate the nonlinear stress response under LAOS flow, the nonlinearity (I3/1) from Fourier transform-rheology as a function of applied shear time (3600 s) was calculated according to changes in both strain amplitude γ0 and frequency ω. The storage modulus G′(t) and loss modulus G″(t) from the conventional rheometer program under various LAOS flow conditions decreased and reached equilibrium as a function of time. This could be attributed to shear alignment of the lamellar smectic A structure. On the contrary, with G′(t) and G″(t), the nonlinearity I3/1(t) showed three different behaviors depending on the magnitude of strain amplitude: (1) Region I: Increased (increased and reached equilibrium), (2) region II: Increased and decreased (showed maximum value; decreased and reached equilibrium), and (3) region III: Decreased (decreased and reached equilibrium) as a function of time. These three different time-dependent behaviors of nonlinearity (I3/1) were shown to be related with the alignment behavior of the lamellar structure. With stress decomposition method, the viscous and elastic stresses of 3600 s were calculated. Viscous and elastic stresses showed different behavior at region I and region III. With an equilibrium value of 3600 s, the G′, G″, and nonlinearity (I3/1) were plotted as a function of strain amplitude, γ0. Interestingly, I3/1(γ0) increased and then decreased (maximum) even though G′(γ0) and G″(γ0) only decreased with increasing strain amplitude. From these results, it can be concluded that LAOS analysis of nonlinear stress, especially I3/1 from FT-rheology, is more sensitive to microstructure than storage modulus G′ and loss modulus G″.

Large amplitude oscillatory shear and Fourier transform rheology analysis of branched polymer melts

In this paper, the predictions of the Pompom constitutive model in medium and large amplitude oscillatory shear (LAOS) are examined using Fourier transform rheology (FTR). FTR is commonly used in combination with small amplitude oscillatory shear to fit linear Maxwell parameters to dynamic moduli, and in this paper, this process is expanded to larger strain amplitudes and to further terms in the Fourier series. For both small and large amplitudes, these higher harmonics are dependent on the nonlinear Pompom parameters and the Pompom parameter space is explored to see how experimental oscillatory shear data can infer molecular detail. In the regime of small and medium strain amplitude, there exists an asymptotic solution to the Pompom equations which depends only on the ratio of the orientation and stretch relaxation times, τb and τs. This asymptotic solution is found to be accurate up to strains of order unity and the branching priority, q, only affects the stress response at larger strains. The Pompom parameters fitted to extensional data are compared to LAOS data for three materials; two lightly branched metallocene catalyzed high density polyethylenes and a densely branched low density polyethylenes. In general, the Pompom model performs well in LAOS but tends to over predict experimental results at high strain amplitudes.

Large amplitudes oscillatory shear (LAOS) behavior of egg white foams with apple pectins and xanthan gum

The study presents the results of research on non-linear rheological properties of foams based on egg white protein, xanthan gum and apple pectin of various levels of methylation. The rheological studies were carried out by means of large amplitude oscillatory shear (LAOS) and Fourier transform rheology (FTR) methods. The obtained foams revealed elastoviscoplastic properties. The analysis of the results allowed determination of yield stress, shear exponents and the Fourier spectra, which enabled estimation of the quantity and intensity of individual harmonics. The Lissajous patterns as well as coefficients of energy dissipation were also demonstrated. The foam containing solely egg white revealed the largest number of harmonics in the Fourier spectrum (17th), whereas supplementation with hydrocolloids induced a decrease in the amount of harmonics (9th). The image of the Fourier spectra was reflected by the Lissajous curves, which gradually acquired an ellipsoidal shape as the hydrocolloid concentration increased. The coefficient of energy dissipation in the function of the deformation amplitude demonstrated a sigmoid dependence and tended towards the value of approximately 0.8 for higher amplitudes. This indicated that the investigated foams were in a flow area. The statistical analysis (two/three-way ANOVA) of the abovementioned values showed that neither the level of methylation nor the pectin concentration in foam influences the yield stress.

Mechanical spectral hole burning in polymer solutions: Comparison with large amplitude oscillatory shear fingerprinting

Large amplitude oscillatory shear (LAOS) fingerprinting of the nonlinear response of polymers and other complex soft matter has proven an excellent tool in the characterization of such materials. The major methods of quantitative characterization of nonlinearity using LAOS are the use of Lissajous-Bowditch (LB) curves and Fourier transform rheology (FTR). Another LAOS-based tool, mechanical spectral hole burning (MSHB), has been developed in our labs to investigate the heterogeneous dynamics of polymer melts and solutions and offers the possibility of a complementary method to the LB and FTR analyses for the fingerprinting of the nonlinear response of polymers and other complex fluids. Here, we present results from an investigation of the MSHB, LB loop, and FTR behaviors of polybutadiene and polystyrene solutions. The goal of the study was to examine similarities and differences in how these methods “fingerprint” the nonlinear response of the different polymer solutions. We find that the vertical holes in the MSHB experiments vary in intensity with the square of the sine wave pump magnitude. This is also true for the third harmonics obtained in the FTR, but the origins are possibly different for the two signatures. We have analyzed the fingerprinting categories as a function of strain amplitude and frequency from the LB loops and higher harmonics of FTR and add an additional feature to the fingerprints that are related to MSHB signatures, which are found to complement the other two methods and add new information to the fingerprinting diagrams.

Flow of concentrated solutions of starlike micelles under large-amplitude oscillatory shear

The non-linear viscoelasticity of concentrated solutions and glasses of soft starlike micelles has been studied by large-amplitude oscillatory shear (LAOS). The non-linear response has been analysed using current schemes of Fourier transform (FT) rheology, and its character has been determined by the phase of the third harmonic contribution to the stress. The limitations of FT rheology and related analysis methods are discussed, and an alternative method is presented that takes into account all the higher harmonics. This method reveals a strain-hardening character of intracycle non-linearities at large strain amplitudes for all volume fractions. We also show that, although the relation of LAOS with steady shear measurements works qualitatively, due to inherent limitations of LAOS, steady shear data cannot be reproduced quantitatively.

Characterization of non-linear rheological behavior of SPI–FG dispersions using LAOS tests and FT rheology

The effect of flaxseed gum (FG) on the rheological and nonlinear stress response behaviors of mixed soy protein isolate (SPI)–flaxseed gum (FG) dispersions were studied. Results showed that the viscosity of the SPI–FG mixed dispersions increased significantly with increase in the FG concentration. Both the shear stress and the apparent viscosity values as a function of shear rate were fitted well using Power law model as expected. The frequency dependence of G′, G′′ and tanδ of soy protein isolate decreased as the FG concentration increased. The large amplitude oscillatory shear (LAOS) test and Fourier transform (FT) rheology analysis showed that the addition of flaxseed gum strongly affected the structure of the SPI–FG mixed dispersion system as shown by deformation of the nonlinear stress response curve and significantly altered magnitude of higher harmonic curve. The addition of FG increased the instantaneous strain softening effect of the SPI–FG mixed dispersion system.

Optimizing the Sensitivity of FT-Rheology to Quantify and Differentiate for the First Time the Nonlinear Mechanical Response of Dispersed Beer Foams of Light and Dark Beer

Abstract Foams are dispersions consisting of a gaseous dispersed phase and a liquid or solid dispersion medium. For the case of beer foam, only the liquid dispersion medium is of interest here. The focus of this work was closed foams that were explored for the first time using Fourier Transform Rheology (FT-Rheology). It was shown that FT-Rheology was able to resolve differences between various brands of beers. While foam rheology is of high interest especially in the food industry and for personal care products, previous investigations were typically made using steady shear or were within the linear oscillatory regime. However, the challenge facing large amplitude oscillatory shear (LAOS) measurements in foams is detection of the resulting extremely low torque related to the higher harmonics. Foams with a high volume fraction of the dispersed gaseous phase generate a LAOS response that is generally quite low, specifically torque values on the order of μN m. Therefore, the LAOS measurements have to be performed with a very sensitive and carefully optimized rheometer. To achieve the results here, the most advanced rheometer ARES G2 from TA Instruments was used because it possesses the highest sensitivity of status quo strain controlled rheometers and is able to measure torques down to 50 nN m. This requirement of high torque resolution limited previous investigations on nonlinear oscillatory shear experiments and makes the experimental results described here both unique and pioneering.

Fourier Transform Rheology as an innovative morphological characterization technique for the emulsion volume average radius and its distribution

This article extends previous works on emulsion characterization via Fourier Transform Rheology. The interest here is on the effects of (i) polydispersity and (ii) high volume fraction (often associated with commercial samples) on the nonlinear rheological behavior. To analyze the effects of polydispersity on the LAOS measurements, the investigated samples were characterized with respect to their volume average radius, 〈R〉43, and the polydispersity index of the distribution. As the nonlinear mechanical emulsion value E0 introduced in the literature is a function of both nonlinear rheological parameters, such as I5/3, as well as emulsion properties including the volume average radius, interfacial tension and viscosities of the matrix and dispersed phase, it is, therefore, a useful tool for emulsion characterization. In addition, the analysis of the higher harmonic ratios, I7/5, has been demonstrated to provide information about the width of the distribution. With respect to the characterization of the high volume fraction samples, these first experiments on commercial w/o-emulsions were shown to relate nonlinear rheological properties to the droplet size and droplet size distribution of highly filled systems, demonstrating that LAOS experiments can give useful insights on the average droplet size and its distribution.

Rheology and enhancement of extrusion of linear and branched polyethylenes using low amount of organoclay

AbstractInteraction between 0.05 wt % organoclay and polyethylenes of different short chain branching (SCB) was studied. Linear rheology (van Gurp‐Palmen plot) was used to study the effect of organoclay on the rheology of polyethylenes. Organoclay had effect only on the van Gurp‐Palmen plot of linear polyethylene. Fourier transform (FT) rheology, extrusion at high‐shear rates in a slit rheometer, transient stress growth analysis, and extensional rheology were conducted to examine the potential of organoclay as a processing aid. Organoclay reduced the transient stress overshoot, normal stress difference, ηo, onset of shear thinning, and extrusion pressure of polyethylene. The reduction was more pronounced in linear polyethylene without branching. Such effects gradually decreased as the branch content increased. The trend was independent of the type of flow (shear or extensional). It was interesting to note that FT rheology was not effective in explaining the impact of organoclay on polyethylene. The work concluded with the proposition that organoclay (as low as 0.05 wt %) was a good processing aid for linear polyethylene and polyethylenes with low content of SCB. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012