A new non-linear parameter Q from FT-Rheology under nonlinear dynamic oscillatory shear for polymer melts system

Hyun, Kyu; Kim, Won-Ho

doi:10.1007/s13367-011-0028-0

Cited by 36 publications

(12 citation statements)

References 26 publications

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“…The viscous modulus for B. subtilis, C. denitrificans and P. aeruginosa show distinct humps at γ = 30%, γ = 0.7% and γ = 25%, which are indicative of Type-III weak strain overshoot. Such behaviour is commonly seen in soft glassy materials and can arise due to structural rearrangements arising within the biofilm 51 . A closer look at the viscous modulus component of the amplitude sweep for CD shows a two step yielding signature at 0.7% and 200% strain, similar to that observed in colloidal systems [64][65][66] , which hypothesises successive bond and cage breaking at two separate strain amplitudes.…”

Section: Resultsmentioning

confidence: 99%

“…By comparing the MAOS regions of different microbial species, once comes to the conclusion that C. denitrificans starts exhibiting nonlinearity at very small strain amplitudes; but the rate of growth of nonlinearity is smaller when compared to any of the other species. For model polymeric systems, like linear polymers a scaling exponent of~2 is usually observed; while a slope of~1.8 has been observed for branched polymer systems 51,70 . Both P. fluorescens and B. subtilis show a scaling of 1.8 indicating a behaviour similar to that of branched polymer networks 51,52,70 .…”

Section: Onset Of Nonlinearity Defined By Medium Amplitude Oscillatormentioning

confidence: 99%

“…For model polymeric systems, like linear polymers a scaling exponent of~2 is usually observed; while a slope of~1.8 has been observed for branched polymer systems 51,70 . Both P. fluorescens and B. subtilis show a scaling of 1.8 indicating a behaviour similar to that of branched polymer networks 51,52,70 . However, one should be careful about drawing such conclusions because biofilms are complex mixtures of multiple polymers.…”

Section: Onset Of Nonlinearity Defined By Medium Amplitude Oscillatormentioning

confidence: 99%

“…Material descriptors like intracycle strain stiffening (or softening) and intracycle shear thickening (or thinning) indices can reveal a unique fingerprint of the material 50 . Owing to higher sensitivity, LAOS also finds application in detection of architecture and branching characteristics of polymer melts [51][52][53] . In the past decade, LAOS has become a canonical technique for quantifying the rheological characteristics of polymers, soft solids, gels, emulsions and various other complex fluids and materials 48,54 .…”

Section: Introductionmentioning

confidence: 99%

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Nonlinear rheological characteristics of single species bacterial biofilms

Jana

Charlton

Eland

et al. 2020

npj Biofilms Microbiomes

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Bacterial biofilms in natural and artificial environments perform a wide array of beneficial or detrimental functions and exhibit resistance to physical as well as chemical perturbations. In dynamic environments, where periodic or aperiodic flows over surfaces are involved, biofilms can be subjected to large shear forces. The ability to withstand these forces, which is often attributed to the resilience of the extracellular matrix. This attribute of the extracellular matrix is referred to as viscoelasticity and is a result of selfassembly and cross-linking of multiple polymeric components that are secreted by the microbes. We aim to understand the viscoelastic characteristic of biofilms subjected to large shear forces by performing Large Amplitude Oscillatory Shear (LAOS) experiments on four species of bacterial biofilms: Bacillus subtilis, Comamonas denitrificans, Pseudomonas fluorescens and Pseudomonas aeruginosa. We find that nonlinear viscoelastic measures such as intracycle strain stiffening and intracycle shear thickening for each of the tested species, exhibit subtle or distinct differences in the plot of strain amplitude versus frequency (Pipkin diagram). The biofilms also exhibit variability in the onset of nonlinear behaviour and energy dissipation characteristics, which could be a result of heterogeneity of the extracellular matrix constituents of the different biofilms. The results provide insight into the nonlinear rheological behaviour of biofilms as they are subjected to large strains or strain rates; a situation that is commonly encountered in nature, but rarely investigated.

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Section: Resultsmentioning

confidence: 99%

Section: Onset Of Nonlinearity Defined By Medium Amplitude Oscillatormentioning

confidence: 99%

Section: Onset Of Nonlinearity Defined By Medium Amplitude Oscillatormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Nonlinear rheological characteristics of single species bacterial biofilms

Jana

Charlton

Eland

et al. 2020

npj Biofilms Microbiomes

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“…Therefore, study properties within non-linear regions could provide information on material structures. Fourier transform (FT)-Rheology is known to be a promising tool to detect small changes in topology and morphology of materials (Hyun et al, 2007;Hyun and Wilhelm, 2009;Kim, 2011, Hyun et al, 2011;Lim et al, 2013;Salehiyan and Hyun, 2013;Salehiyan et al, 2014a). FT-Rheology is a powerful method to quantify non-linear responses based on its sensitivity to stress signal.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear behavior of PP/PS blends with and without clay under large amplitude oscillatory shear (LAOS) flow

Salehiyan

Song

Hyun

2015

Korea-Aust. Rheol. J.

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Dynamic oscillatory measurement, i.e., small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) test was used to investigate linear and non-linear viscoelastic properties of Polypropylene (PP)/Polystyrene (PS) blends with and without 5 wt.% clay (C20A). Fourier transform (FTRheology), Lissajous curves and stress decomposition methods were used to analyze non-linear responses under LAOS flow. Composition effects of blends were investigated prior to compatibilization effects. Elevated concentrations of dispersed phase (PS) increased the moduli G'(ω) from SAOS test and G*(γ 0 ) from LAOS test of the blends as well as strain thinning behavior. Interestingly, addition of 5 wt.% clay (C20A) boosted moduli of the blends as well as led to similar strain thinning behaviors among the PP/PS/C20A blends, except for the (90/10) PP/PS blend. The latter did not show improved rheological properties despite morphological improvements, as shown by SEM. Results from SEM and improved rheological properties of PP/PS/C20A blends revealed the compatibilization effects of clay (C20A) particles regardless of size reduction mechanisms. Third relative intensities (I 3/1 ) from FT-rheology were found to be sensitive to clay (C20A) additions for the (70/30) and (30/70) PP/PS blends. Similarly, Lissajous curves could detect changes upon clay (C20A) addition, specifically at lower strain amplitudes whereupon addition of 5 wt.% clay resulted in the closed loops of Lissajous curves showing a more ellipsoidal shape due to increased elasticity in the blends. However, detection of these changes at larger strain amplitudes was more challenging. Therefore, stress decomposition (SD) method was applied for more precise characterization as it decomposes the total stress (σ) into elastic stress (σ') and viscous stress (σ''). Using SD method, elastic stress was more distorted, especially, strain hardening, while the total stress response remained almost unchanged at larger strain amplitudes.

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Non‐linear rheological response as a tool for assessing dispersion in polypropylene/polycaprolactone/clay nanocomposites and blends made with sub‐critical gas‐assisted processing

Ellingham

Yilmaz

Turng

2019

Polymer Engineering & Sci

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Polypropylene (PP) was blended with polycaprolactone (PCL) and nanoclay (NC) in a twin‐screw extruder (TSE) using a traditional extrusion process and a sub‐critical gas‐assisted process (SGAP). SGAP is a new and facile processing method that injects compressed gas (CO2 or N2) at low pressures (~10 bars) into the barrel of the extruder to induce rapid and repetitive foaming and resolubilization as the melt travels through regions of high pressure and low pressure. Bubble expansion during foaming introduces an equibiaxial elongational flow not otherwise generated in TSE, adding to the total stress the polymer matrix can exert to break up nanoparticle agglomerates and reduce the droplet size of secondary polymers in blends. Impact, morphology, and X‐ray diffraction (XRD) properties confirmed a smaller PCL phase droplet size and an increase in dispersion of the NC when SGAP was used. Standard small amplitude oscillatory (SAOS) rheological tests for the storage modulus G′ were not sensitive enough to discern the difference between the traditionally extruded samples and the SGAP samples. However, the zero‐strain non‐linearity parameter, Q0, determined by the Fourier‐Transform rheology, was able to distinguish the enhanced dispersive and mixing capabilities of SGAP. Practical implications of SGAP and Fourier‐Transform (FT) rheology are also discussed in this paper. POLYM. ENG. SCI., 60:55–60, 2020. © 2019 Society of Plastics Engineers

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A new non-linear parameter Q from FT-Rheology under nonlinear dynamic oscillatory shear for polymer melts system

Cited by 36 publications

References 26 publications

Nonlinear rheological characteristics of single species bacterial biofilms

Nonlinear rheological characteristics of single species bacterial biofilms

Nonlinear behavior of PP/PS blends with and without clay under large amplitude oscillatory shear (LAOS) flow

Non‐linear rheological response as a tool for assessing dispersion in polypropylene/polycaprolactone/clay nanocomposites and blends made with sub‐critical gas‐assisted processing

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