Investigation of nonlinear rheological behavior of linear and 3-arm star 1,4-cis-polyisoprene (PI) under medium amplitude oscillatory shear (MAOS) flow via FT-rheology

Song, Hyeong Yong; Nnyigide, Osita Sunday; Salehiyan, Reza; Hyun, Kyu

doi:10.1016/j.polymer.2016.04.052

Cited by 27 publications

(29 citation statements)

References 55 publications

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“…Intra-cycle nonlinear viscoelastic characterization can provide insightful information regarding nanocomposites’ structural features [ 52 , 56 , 57 , 58 , 59 , 60 ]. In this section, we utilized the stress decomposition method to interpret the intra-cycle viscoelastic responses of our nanocomposites to further elucidate their microstructure.…”

Section: Resultsmentioning

confidence: 99%

“…Beyond the linear viscoelastic region, due to the excitation of higher harmonics in the output shear stress waveform, stress response is not a perfect sinusoid. Therefore, by tracing the distortion of the intra-cycle output stress waveform, useful information about the microstructural features can be obtained [ 25 , 60 , 61 ]. A useful way of representing the intra-cycle output stress waveform is in the form of Lissajous–Bowditch (LB) loops.…”

Section: Resultsmentioning

confidence: 99%

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A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

et al. 2021

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This study intends to reveal the significance of the catalyst to substrate ratio (C/S) on the structural and electrical features of the carbon nanotubes and their polymeric nanocomposites. Here, nitrogen-doped carbon nanotube (N-MWNT) was synthesized via a chemical vapor deposition (CVD) method using three ratios (by weight) of iron (Fe) catalyst to aluminum oxide (Al2O3) substrate, i.e.,1/9, 1/4, and 2/3, by changing the Fe concentration, i.e., 10, 20, and 40 wt.% Fe. Therefore, the synthesized N-MWNT are labelled as (N-MWNTs)10, (N-MWNTs)20, and (N-MWNTs)40. TEM, XPS, Raman spectroscopy, and TGA characterizations revealed that C/S ratio has a significant impact on the physical and chemical properties of the nanotubes. For instance, by increasing the Fe catalyst from 10 to 40 wt.%, carbon purity increased from 60 to 90 wt.% and the length of the nanotubes increased from 1.2 to 2.6 µm. Interestingly, regarding nanotube morphology, at the highest C/S ratio, the N-MWNTs displayed an open-channel structure, while at the lowest catalyst concentration the nanotubes featured a bamboo-like structure. Afterwards, the network characteristics of the N-MWNTs in a polyvinylidene fluoride (PVDF) matrix were studied using imaging techniques, AC electrical conductivity, and linear and nonlinear rheological measurements. The nanocomposites were prepared via a melt-mixing method at various loadings of the synthesized N-MWNTs. The rheological results confirmed that (N-MWNTs)10, at 0.5–2.0 wt.%, did not form any substantial network through the PVDF matrix, thereby exhibiting an electrically insulative behavior, even at a higher concentration of 3.0 wt.%. Although the optical microscopy, TEM, and rheological results confirmed that both (N-MWNTs)20 and (N-MWNTs)40 established a continuous 3D network within the PVDF matrix, (N-MWNTs)40/PVDF nanocomposites exhibited approximately one order of magnitude higher electrical conductivity. The higher electrical conductivity of (N-MWNTs)40/PVDF nanocomposites is attributed to the intrinsic chemical features of (N-MWNTs)40, such as nitrogen content and nitrogen bonding types.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

et al. 2021

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“…In the current study, we investigated the MAOS behavior of the comb and bottlebrush PS used in Abbasi, Faust, Riazi and Wilhelm [21]. Recently, MAOS rheology has been used to characterize different polymer architectures, such as linear [27,28], 3-arm star [29] and comb [16,30]. When the relative intrinsic nonlinearity Q 0 , one of MAOS material parameters, was plotted as a function of excitation frequency, it showed a different number of local peaks depending on the number of terminal relaxation processes in polymer architectures.…”

Section: Introductionmentioning

confidence: 99%

Small and Medium Amplitude Oscillatory Shear Rheology of Model Branched Polystyrene (PS) Melts

et al. 2020

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Linear and nonlinear rheological properties of model comb polystyrenes (PS) with loosely to densely grafted architectures were measured under small and medium amplitude oscillatory shear (SAOS and MAOS) flow. This comb PS set had the same length of backbone and branches but varied in the number of branches from 3 to 120 branches. Linear viscoelastic properties of the comb PS were compared with the hierarchical model predictions. The model underpredicted zero-shear viscosity and backbone plateau modulus of densely branched comb with 60 or 120 branches because the model does not include the effect of side chain crowding. First- and third-harmonic nonlinearities reflected the hierarchy in the relaxation motion of comb structures. Notably, the low-frequency plateau values of first-harmonic MAOS moduli scaled with M w − 2 (total molecular weight), reflecting dynamic tube dilution (DTD) by relaxed branches. Relative intrinsic nonlinearity Q0 exhibited the difference between comb and bottlebrush via no low-frequency Q0 peak of bottlebrush corresponding to backbone relaxation, which is probably related to the stretched backbone conformation in bottlebrush.

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“…For polymers in particular, LAOS is complementary to small-amplitude measurements, and results are a complex function of molecular architecture such as linear [14], star [15], and comb architectures [16] and can be used to quantify the level of branching in industrial resins such as metallocene-catalyzed sparsely branched HDPEs [17,18] or tubular-reacted randomly branched LDPEs [18,19]. However, crucially, LAOS is not yet a standard analytical tool for characterizing molecular architecture.…”

Section: Introductionmentioning

confidence: 99%

“…The molecular stress-function (MSF) theory has also been shown to be capable of capturing extensional and LAOS rheology simultaneously [19]. For the MAOS regime both the Pom-pom and MSF theories have been shown to broadly capture the intensity of I 3/1 over a range of frequencies for a range of materials from monodisperse linear and star-arm to randomly branched polymers [14,15,17]. A limitation of all these approaches is that fitting is required to match theory to LAOS data; typically the parameters are set by a different rheometric experiment and the fits are "multimodal" in form.…”

Section: Introductionmentioning

confidence: 99%

Chain-stretch relaxation from low-frequency Fourier transform rheology

Reynolds

Hoyle

Thompson

et al. 2020

Phys. Rev. Research

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Medium-or large-amplitude oscillatory shear (MAOS and LAOS, respectively) is sensitive to polymer chain structure, yet poses unsolved challenges for a priori structural characterization. We present a MAOS protocol applied to near-monodisperse linear polymer melts, from which chain-stretch relaxation, a key structural feature, is discernible. The third harmonics of MAOS frequency sweeps are decomposed into real and imaginary components and found to obey time-temperature superposition. Significantly, these third harmonic features occur at low frequency and are readily accessible with standard rheometers. For materials where phase transitions restrict the use of time temperature superposition, this method has potential to greatly increase the scope of rotational rheometry for structural analysis of polymers. However, the relationship between MAOS data and characteristic relaxation times is complex, and to elucidate this, a modeling approach is required. The GLaMM molecular tube-based model of linear entangled melt rheology and structure, which has no free parameters, closely follows the form of our experimental results for the third harmonics and contains discriminatory features which depend only on the polymer's chain stretch relaxation time. However, we find fundamental differences in magnitude and the frequency dependence of the third harmonics which must be resolved in order to fully understand the molecular basis of the stress response and quantitatively study chain stretch.

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Investigation of nonlinear rheological behavior of linear and 3-arm star 1,4-cis-polyisoprene (PI) under medium amplitude oscillatory shear (MAOS) flow via FT-rheology

Cited by 27 publications

References 55 publications

A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

A Simple Approach to Control the Physical and Chemical Features of Custom-Synthesized N-Doped Carbon Nanotubes and the Extent of Their Network Formation in Polymers: The Importance of Catalyst to Substrate Ratio

Small and Medium Amplitude Oscillatory Shear Rheology of Model Branched Polystyrene (PS) Melts

Chain-stretch relaxation from low-frequency Fourier transform rheology

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