Dynamic Rheological Properties of Concentrated Chitosan Soltions

2004 ◽  
Vol 14 (3) ◽  
pp. 140-147 ◽  
Author(s):  
A. Martínez-Ruvalcaba ◽  
E. Chornet ◽  
D. Rodrigue
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Complex Viscosity ◽  
Maxwell Model ◽  
Viscous Effects ◽  
Experimental Conditions ◽  
Low Frequencies ◽  
Wide Range ◽  
Generalized Maxwell Model ◽  
Different Temperatures

AbstractA detailed analysis of the dynamic flow properties of chitosan in solution at different temperatures (25 - 45°C), chitosan concentration (0.5% - 2.0%), solvent type (acetic, lactic, and hydrochloric acid), and ionic strength (0 and 0.2M NaCl) has been undertaken. The storage modulus, G’, loss modulus, G’’ and complex viscosity, η* have been determined over a wide range of frequencies and the results are presented using master curves. For the conditions studied, at low frequencies chitosan solutions show a constant complex viscosity which decreases as frequency increases. Likewise, storage modulus, G’ and loss modulus, G’’ increase as frequency increases with G’’ being always greater than G’ (η’ > η’’) indicating that viscous effects are more important than elastic effects. For modelling the oscillatory-shear results we used the generalized Maxwell model. Two empirical equations were used to correlate the data: Cox-Merz rule for viscosity and Laun's rule for primary normal stress difference. Both relations were found to represent our data for the experimental conditions studied.

Viscoelastic Properties of Thixotropic Semisolid Alloy Relating the Microstructure

2019 ◽  
Vol 285 ◽  
pp. 380-384
Author(s):  
Gerardo Sanjuan-Sanjuan ◽  
Ángel Enrique Chavez-Castellanos
Keyword(s):  
Storage Modulus ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Complex Viscosity ◽  
Plateau Modulus ◽  
Complex Shear ◽  
Different Temperatures ◽  
Semisolid Alloy ◽  
The Subject

The subject of this work is to investigate viscoelastic properties such as loss modulus (G ́ ́), storage modulus (G ́), complex shear modulus (G*), complex viscosity (η*) and loss angle () at different temperatures by means of a small-amplitude oscillatory test. These properties allow to provide information about materials structure. For this purpose, we employed a tin-lead alloy (Sn-15%Pb) which exhibits a similar microstructure to aluminum alloys and is the classic alloy for semisolid thixotropic studies. It is interesting to note that the Sn-15%Pb alloy exhibits a slightly decrease in storage modulus (G ́) over the entire frequency (0.01-10Hz) at high temperatures, showing its viscoelastic behavior. In addition, a detailed analysis of master curves (oscillatory tests) was made to relate the semisolid microstructure (solid fraction) with the plateau modulus (GN0) which is directly related with both molecular weight or percolation threshold in polymer and gels science respectively.

Physical Modelling and Identification of Polymer Viscoelastic Behaviour above Glass Transition Temperature and Application to the Numerical Simulation of the Hot Embossing Process

2013 ◽  
Vol 554-557 ◽  
pp. 1763-1776 ◽  
Author(s):  
Gang Cheng ◽  
Jean Claude Gelin ◽  
Thierry Barrière
Keyword(s):  
Numerical Simulation ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Maxwell Model ◽  
Hot Embossing ◽  
Finite Element Software ◽  
Generalized Maxwell Model

The experimental processing parameters, such as applied pressure and forming temperature have been analysed during polymer hot embossing of micro-cavities. The viscoelastic characteristics of polymer above the glass transition temperature have been investigated with the classical viscoelastic models. Generalized Maxwell Model has been used to describe polymer behaviours in the glass transition temperature range. The parameters include relaxation time, storage modulus and loss modulus of the Generalized Maxwell Model that have been introduced. The identification of polymer characteristics has been carried out through Dynamic Mechanical Analysis (DMA). The storage modulus, the loss modulus and the damping factor of the selected polymer have been obtained with different imposed frequencies. The master curve of complex modulus has been obtained by applying the time temperature superposition principle. The experimental data has been identified with optimized fitting parameters of Generalized Maxwell Model. A proper agreement between the experimental measurement and the identification of viscoelastic model is observed. The resulting constitutive equations have been implemented in finite element software in order to achieve the numerical simulation of the hot embossing process.

Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

2020 ◽  
Vol 16 (4) ◽  
pp. 462-469
Author(s):  
Zhaleh Sheidaei ◽  
Bahareh Sarmadi ◽  
Seyede M. Hosseini ◽  
Fardin Javanmardi ◽  
Kianoush Khosravi-Darani ◽  
...  
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Textural Properties ◽  
Complex Viscosity ◽  
Sensory Properties ◽  
Modified Starch ◽  
Consumer Health ◽  
Added Sugar ◽  
Textural Parameters

<P>Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. </P><P> Objective: This study aims to investigate the effects of &#954;-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. </P><P> Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan &#948;) and complex viscosity (&#951;*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. </P><P> Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of &#954;-carrageenan and modified starch caused an increase in G′ and G″ as well as &#951;* and a decrease in tan &#948;. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% &#954;-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. </P><P> Conclusion: It can be concluded that the concentration of &#954;-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.</P>

Rheological studies of uncured epoxy–organoclay nanocomposite coatings

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Davood Zaarei ◽  
Ali Asghar Sarabi ◽  
Farhad Sharif ◽  
Seyed Mahmoud Kassiriha ◽  
Mohsen Moazzami Gudarzi
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Film Formation ◽  
Flow Behavior ◽  
Complex Viscosity ◽  
Nanocomposite Coating ◽  
Nanocomposite Coatings ◽  
Strong Increase ◽  
Polymeric Fluids ◽  
Shear Mixing

AbstractWe investigated the influence of loading two different types of organoclay on the linear viscoelastic properties of an uncured epoxy nanocomposite coating. Meanwhile, the effect of sonication in the dispersion process on the characteristics of nanocomposite has been studied. To achieve fully dispersed structures of clay-epoxy, we applied high shear mixing and high-intensity ultrasound during the synthesis of clay-epoxy nanocomposites.The flow properties of the compositions with clay loadings more than 4 wt% of low CEC quaternary ammonium modified clay, as analyzed by rheomechanical spectroscopy (RMS), showed a solid-like behavior. While the neat resin system exhibited Newtonian flow, some nanodispersed coatings exhibited pseudo plastic flow behavior, typical of polymeric fluids such as gels and pastes. With varying the type of the clay the resultant coatings exhibited a storage modulus ranging from 0.01 to over 400 Pa and a loss modulus ranging from 4 to over 200 Pa. Moreover, the complex viscosity was ranging from 12 to 1100 Pas as the clay loading increased from 0 to 8wt %. The strong increase in modulus of one type of the clays was due to the mainly intercalated and dispersed silicate platelets. The increase rate in storage modulus of these compositions decreased at higher organoclay loadings and was not linear. These results can lead to the prediction of film formation properties and application conditions of these nanocomposite coatings

Dynamic Rheological Behaviors of the Bone Scaffold Reinforced by Chitin Fibres

2005 ◽  
Vol 475-479 ◽  
pp. 2387-2390 ◽  
Author(s):  
X.M. Li ◽  
Qing Ling Feng
Keyword(s):  
Viscoelastic Properties ◽  
Loss Factor ◽  
Complex Modulus ◽  
Loss Modulus ◽  
Complex Viscosity ◽  
Materials Processing ◽  
Bone Scaffold ◽  
Rheological Behaviors ◽  
Wide Range ◽  
Yielding Behavior

In this study, a novel bioabsorbable porous bone scaffold reinforced by chitin fibres was prepared, the porosity of which is about 90 % and the pore size is approximately 200µm. The Advanced Rheological Enlarged System (ARES) was used to study the dynamic rheological behaviors of the ropy materials which would be made into the reinforced scaffold. The increase of the fibres’ volume content (Cf) enhanced the complex modulus (G*) and complex viscosity (h*) of the materials, the reason of which is that the fibres formed networks in the materials. When Cf increased from 35 % to 45 %, the storage modulus (G’) and loss modulus (G’’) curve showed obvious yielding behavior, which indicates that G’ and G’’ of the materials are hardly variable in a wide range. When Cf was more than 35 %, the loss factor (tand) was obviously lower than 1 and the materials exhibited viscoelastic properties, which result in a disadvantage for materials’ processing.

Study of the rheological properties of polypropylene/talc/nanoclay ternary hybrid nano composites

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
M. Alavi ◽  
M. Esfandeh ◽  
J. Morshedian ◽  
Y. Jahani
Keyword(s):  
Loss Modulus ◽  
Rheological Behaviour ◽  
Complex Viscosity ◽  
Xrd Analysis ◽  
Ternary Blend ◽  
Hydrodynamic Effect ◽  
Low Frequencies ◽  
Melt Compounding ◽  
Twin Screw ◽  
Simultaneous Use

AbstractModification of polypropylene (PP) properties by the addition of particulate fillers has been of interest for several years. In the recent years, the simultaneous use of nanofillers and conventional reinforcing fillers and study of the effect of these hybrid systems on various properties of composite has gained the attention of many researchers. In this paper, nanocomposites based on PP/Talc/Nanoclay were prepared at various filler levels via melt compounding of the ingredients in a twin-screw extruder. Here, a polypropylene grafted maleic anhydride (PP-g-MA)/Nanoclay master batch was prepared at 140 oC. The masterbatch was then used to prepare ternary compounds through a simultaneous feeding system, in a ZSK extruder at 210 °C. The extrudate was granulated and then re-extruded through a slit die, to prepare the test specimens. SEM and XRD analysis were used to characterise the systems. Rheological behaviour of the specimens was studied using a parallel plate rheometer. In the ternary blend on comparing with the neat PP, the complex viscosity (η*) is increased with increasing overall filler content; however, at low frequencies this increase is governed by the content of nano filler while at high frequencies it is mainly determined by talc content. A similar trend was also observed for the variations of storage modulus (G′) and loss modulus (G″) with frequency. The results showed that the simultaneous use of nano and micro size fillers considerably affects the melt elasticity. It is believed that the hybrid system increases the hydrodynamic effect of filler particles in the molecular motion of the polymer.

scholarly journals Rheological Properties of HDPE based Thermoplastic Polymeric Nanocomposite Reinforced with Multidimensional Carbon-based Nanofillers

2021 ◽  
Vol 12 (4) ◽  
pp. 5709-5715
Keyword(s):  
Rheological Properties ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Complex Viscosity ◽  
Damping Factor ◽  
Equal Weight ◽  
Functional Elements ◽  
Weight Percentage ◽  
Potential Applications ◽  
Rheological Test

The present investigation focused on the evaluation of rheological properties HDPE reinforced with equal weight percentage (i.e., 0.1 wt. %) of Nano-diamond (0D), Carbon nanotubes (1D), and Graphite Nano-platelets (2D) multidimensional nanofillers. The results like storage modulus, loss modulus, Tan delta, and complex viscosity results expounded from the rheological test with a frequency sweep from 10-1 to 102 rad/s. The highest storage modulus was perceived by 0.1 CNT-based composites, i.e., 18408 Pa, which decreased to 19, 52, and 85 % for 0.1 GNP, 0.1 ND, and pure, respectively. A similar trend was observed for loss modulus and damping factor results. The shear-thinning behavior observed in viscosity results and the addition of ND nanofillers improve the viscosity to a large amount. The potential applications of the composites include polymer gears, landing mats, cams, and various functional elements.

Dynamic rheological behavior of polyfluorinated ethylene propylene/polypropylene blend melts

2016 ◽  
Vol 30 (2) ◽  
pp. 273-285 ◽  
Author(s):  
JZ Liang ◽  
W Peng ◽  
KJ Wang
Keyword(s):  
Loss Modulus ◽  
Weight Fraction ◽  
Complex Viscosity ◽  
Experimental Conditions ◽  
Ethylene Propylene ◽  
Twin Screw ◽  
The Difference ◽  
Tan Δ ◽  
Pp Blends ◽  
The Relationship

The polyfluorinated ethylene propylene (FEP)/polypropylene (PP) blend was compounded at melt state in a twin-screw extruder. The melt dynamic viscoelasticity of FEP/PP blends was measured using a Bohlin rheometer with the extended temperature option under experimental conditions with temperature scope from 270°C to 280°C and shear frequency ( ω) varying from 10−2 to 101 s−1. The results showed that the shear storage modulus ( G′) and shear loss modulus ( G″) increased nonlinearly, while the dynamic complex viscosity ( η*) decreased slightly with increasing ω. The G′ and G″ were an exponential function of ω. The G′, G″, and η* of the blend melts decreased with an addition of the PP weight fraction [Formula: see text], and the relationship between them might be expressed by a multinomial third-order equation. This phenomenon might be attributed to the difference in viscoelasticity between the FEP melt and PP melt. The value of tan δ of the blend melts achieved the maximum at about 100 s−1.

scholarly journals Viscoelastic Properties of Asphalt Mixtures with Different Modifiers at Different Temperatures Based on Static Creep Tests

2019 ◽  
Vol 9 (20) ◽  
pp. 4246 ◽  
Author(s):  
Yongchun Cheng ◽  
He Li ◽  
Liding Li ◽  
Yuwei Zhang ◽  
Haitao Wang ◽  
...  
Keyword(s):  
Viscoelastic Properties ◽  
Asphalt Mixture ◽  
Maxwell Model ◽  
Asphalt Mixtures ◽  
Creep Tests ◽  
Kelvin Model ◽  
Static Creep ◽  
Generalized Maxwell Model ◽  
Different Temperatures ◽  
Generalized Kelvin Model

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified asphalt mixture (SBSAM) were tested and calculated by the static creep tests. And the creep compliances of the three asphalt mixtures at −20 °C, −10 °C, and 0 °C are deducted by the time–temperature equivalence principle (TTEP) and Arrhenius equation. Further, the relaxation modulus of the three asphalt mixtures from −20 °C to 50 °C at 10 °C increments are calculated by the convolution integral and Simpson method. Subsequently, the Burgers model, the generalized Kelvin model, and the generalized Maxwell model are applied to analyze the viscoelastic properties of the three asphalt mixtures at different temperatures. The results show that the generalized Kelvin model and the generalized Maxwell model are superior to the Burgers model in describing the variation of viscoelastic properties of asphalt mixtures with loading time. At low temperatures, asphalt mixtures have excellent properties in resisting permanent deformation and releasing internal stress. Besides, the addition of SBS modifier and compound diatomite and basalt fibers modifier can significantly raise the viscosity η1 and the elastic modulus E1 of the asphalt mixture, respectively.

Modeling of the Linear Viscoelastic Behavior of Partially Hydrogenated Polymer-Modified Asphalts

2007 ◽  
Vol 80 (2) ◽  
pp. 340-364 ◽  
Author(s):  
M. A. Vargas ◽  
R. Herrera ◽  
O. Manero
Keyword(s):  
Relaxation Times ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Low Frequencies ◽  
Emulsion Model ◽  
Wide Range ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic ◽  
Polymer Modified Asphalt ◽  
Styrene Butadiene

Abstract The modeling of the linear viscoelastic behavior of asphalt modified with 8 wt % of partially hydrogenated poly (styrene-butadiene-styrene) triblock copolymers is analyzed. Time-temperature superposition renders master curves in a wide range of frequencies and temperatures, from which a logarithmic distribution of relaxation times is obtained using the multimode Maxwell model. In addition, the linear viscoelastic data is analyzed with an emulsion model and agreement is only found at high frequencies, where the contribution from interfacial tension is negligible. Enhanced polymer-asphalt interactions at low frequencies evidenced by a decreasing limiting slope of the storage modulus in the terminal region are not predicted by the emulsion model, and relative agreement is found considering two viscoelastic phases. The Cole-Cole representation and the fractional Maxwell model predict the viscosity of asphalt in the complex plane, but strong asymmetry in the semicircular arcs is found in the polymer-modified asphalt blends. The Havriliak-Negami model accounts for asymmetric arcs and represents the data better in specific ranges of frequency.

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