Heterogeneous Blends of Polymers. Rheology and Morphology

1976 ◽  
Vol 49 (1) ◽  
pp. 93-104 ◽  
Author(s):  
G. N. Avgeropoulos ◽  
F. C. Weissert ◽  
P. H. Biddison ◽  
G. G. A. Böhm
Keyword(s):  
Shear Modulus ◽  
Rheological Behavior ◽  
Viscoelastic Properties ◽  
Practical Interest ◽  
Relative Importance ◽  
Network Parameters ◽  
Blend Morphology ◽  
Molecular Interpretation

Abstract A single polymer pair (BR and EPDM) was used to confirm experimentally rheology-morphology relationships that have been previously gleaned from comparison of a variety of blend systems. The relative importance of the primary factors which govern blend morphology (composition and relative mixing viscosity of the components) was determined over the range of practical interest. In addition, correlation of mixing rheology with more accurate and complete shear modulus data allowed (a) molecular interpretation of rheological behavior in terms of network parameters, such as physical entanglements, and (b) estimation of the elastic and loss components of the shear modulus during mixing. An attempt was made at explaining the dependence of blend morphology on the viscoelastic properties of the components in terms of a fracture or tearing mechanism.

Acoustic Scattering by a Fluid-Encapsulating Spherical Viscoelastic Membrane Including Thermoviscous Effects

2005 ◽  
Vol 21 (4) ◽  
pp. 205-215 ◽  
Author(s):  
Seyyed M. Hasheminejad
Keyword(s):  
Viscoelastic Material ◽  
Viscoelastic Properties ◽  
Scattering Problem ◽  
Acoustic Scattering ◽  
Closed Form Solution ◽  
Practical Interest ◽  
Directivity Pattern ◽  
Form Solution ◽  
Heat Conducting ◽  
Harmonic Field

AbstractThis study provides a general analysis for scattering of a planar monochromatic compressional sound wave by a fluid-filled viscoelastic spherical membrane immersed in an unbounded viscous heat-conducting compressible fluid. The thermoviscous effects in the fluid are incorporated by application of a thin boundary layer model. The dynamic viscoelastic properties of the spherical membrane are rigorously taken into account in the solution of the acoustic-scattering problem. Havriliak-Negami model for viscoelastic material behaviour along with the appropriate wave-harmonic field expansions and the pertinent boundary conditions are employed to develop a closed-form solution in form of infinite series. Subsequently, the basic acoustic quantities, such as the scattered far-field pressure directivity pattern, and the scattering cross section are evaluated for given sets of viscoelastic material properties. Numerical results clearly indicate that, in addition to the traditional fluid thermoviscosity-related mechanisms, dynamic viscoelastic properties of the obstacle can be of significance in sound scattering. The presented analysis is of practical interest in development of contrast agents for echocardiographic research with potential clinical applications.

scholarly journals Rheological behavior and antiarthritic activity of Pterodon pubescens nanoemulsion

2020 ◽  
Vol 9 (10) ◽  
pp. e179108119
Author(s):  
Paulo Roberto Nunes de Goes ◽  
Jaqueline Hoscheid ◽  
Saulo Euclides Silva-Filho ◽  
Diego Lacir Froehlich ◽  
Bruna Luíza Pelegrini ◽  
...  
Keyword(s):  
Rheological Behavior ◽  
Viscoelastic Properties ◽  
Elastic Characteristic ◽  
Cell Recruitment ◽  
Joint Cavity ◽  
Creep And Recovery ◽  
Inflammatory Agent ◽  
End Of Treatment ◽  
Different Doses

Pterodon pubescens, popularly known as "sucupira", it is traditionally used as anti-inflammatory agent. This work aimed to evaluate the in vivo antiarthritic properties of a P. pubescens oil nanoemulsion and the rheological behavior of the developed system. The viscoelastic properties, creep and recovery were evaluated by dynamic oscillatory tests. The antiarthritic activity of the nanoemulsion was evaluated by the zymozan-induced arthritis model, at three different doses (25, 50 and 125 mg/kg/day). P. pubescens oil nanoemulsion has been shown to decrease cell recruitment to a joint cavity and increased cartilaginous regeneration at the end of treatment of the dose of 50 mg/kg. The evaluation of the behaviour of deformation allowed to observe that the P. pubescens nanoemulsion presents predominantly elastic characteristic. These findings demonstrate the potential of P. pubescens and nanotechnology in the development of new antiarthritic drugs.

scholarly journals Micromechanical Prediction Model of Viscoelastic Properties for Asphalt Mastic Based on Morphologically Representative Pattern Approach

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Zhichen Wang ◽  
Naisheng Guo ◽  
Xu Yang ◽  
Shuang Wang
Keyword(s):  
Shear Modulus ◽  
Prediction Model ◽  
Viscoelastic Properties ◽  
Volume Fraction ◽  
Complex Modulus ◽  
Homogenization Theory ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Low Frequencies ◽  
Asphalt Mastic

This paper is devoted to the introduction of physicochemical, filler size, and distribution effect in micromechanical predictions of the overall viscoelastic properties of asphalt mastic. In order to account for the three effects, the morphologically representative pattern (MRP) approach was employed. The MRP model was improved due to the arduous practical use of equivalent modulus formula solution. Then, a homogeneous morphologically representative model (H-MRP) with the explicit solution was established based on the homogenization theory. Asphalt mastic is regarded as a composite material consisting of filler particles coated structural asphalt and free asphalt considering the physicochemical effect. An additional interphase surrounding particles was introduced in the H-MRP model. Thus, a modified H-MRP model was established. Using the proposed model, a viscoelastic equation was derived to predict the complex modulus and subsequently the dynamic modulus of asphalt mastic based on the elastic-viscoelastic correspondence principle. The dynamic shear rheological tests were conducted to verify the prediction model. The results show that the predicted modulus presents an acceptable precision for asphalt mastic mixed with 10% and 20% fillers volume fraction, as compared to the measured ones. The predicted modulus agrees reasonably well with the measured ones at high frequencies for asphalt mastic mixed with 30% and 40% fillers volume fraction. However, it exhibits underestimated modulus at low frequencies. The reasons for the discrepancy between predicted and measured dynamic shear modulus and the factors affecting the dynamic shear modulus were also explored in the paper.

Enabling Applications of Covalent Adaptable Networks

2019 ◽  
Vol 10 (1) ◽  
pp. 175-198 ◽  
Author(s):  
Matthew K. McBride ◽  
Brady T. Worrell ◽  
Tobin Brown ◽  
Lewis M. Cox ◽  
Nancy Sowan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Rheological Behavior ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Shape Memory Polymers ◽  
Dynamic Reaction ◽  
Chemical Stimuli ◽  
Applied Fields ◽  
Covalent Crosslinks

The ability to behave in a fluidlike manner fundamentally separates thermoset and thermoplastic polymers. Bridging this divide, covalent adaptable networks (CANs) structurally resemble thermosets with permanent covalent crosslinks but are able to flow in a manner that resembles thermoplastic behavior only when a dynamic chemical reaction is active. As a consequence, the rheological behavior of CANs becomes intrinsically tied to the dynamic reaction kinetics and the stimuli that are used to trigger those, including temperature, light, and chemical stimuli, providing unprecedented control over viscoelastic properties. CANs represent a highly capable material that serves as a powerful tool to improve mechanical properties and processing in a wide variety of polymer applications, including composites, hydrogels, and shape-memory polymers. This review aims to highlight the enabling material properties of CANs and the applied fields where the CAN concept has been embraced.

scholarly journals Revisiting Hartert’s 1962 Calculation of the Physical Constants of Thrombelastography

2015 ◽  
Vol 23 (3) ◽  
pp. 201-210 ◽  
Author(s):  
Gerald Hochleitner ◽  
Ken Sutor ◽  
Caroline Levett ◽  
Harald Leyser ◽  
Christoph J. Schlimp ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Strain Amplitude ◽  
Viscoelastic Properties ◽  
Blood Clot ◽  
Assessment Tools ◽  
Normal Blood ◽  
Clot Strength ◽  
Physical Constants ◽  
Additional Value

Thrombelastography (TEG)/thromboelastometry (ROTEM) devices measure viscoelastic clot strength as clot amplitude (A). Transformation of clot amplitude into clot elasticity (E with TEG; CE with ROTEM) is sometimes necessary (eg, when calculating platelet component of the clot). With TEG, clot amplitude is commonly transformed into shear modulus (G; expressed in Pa or dyn/cm2) as follows: G = (5000 × A)/(100 – A). Use of the constant “5000” stems from Hartert's 50-year-old calculation of G for a normal blood clot. We question the value of calculating G as follows: (1) It may be questioned whether TEG/ROTEM analysis enable measurement of elasticity because viscosity may also contribute to clot amplitude. (2) It has been suggested that absolute properties of a blood clot cannot be measured with TEG/ROTEM analysis because the strain amplitude applied by the device is uncontrolled and changes during the course of coagulation. (3) A review of the calculation of G using Hartert's methods and some updated assumptions suggests that the value of 5000 is unreliable. (4) Recalculation of G for the ROTEM device yields a different value from that with Hartert TEG, indicating a degree of inaccuracy with the calculations. (5) Shear modulus is simply a multiple of E/CE and, because of the unreliability of G in absolute terms, it provides no additional value versus E/CE. The TEG and ROTEM are valuable coagulation assessment tools that provide an evaluation of the viscoelastic properties of a clot, not through measuring absolute viscoelastic forces but through continuous reading of the clot amplitude relative to an arbitrary, preset scale.

Rheology of Ceramic Suspensions with Biopolymeric Gelling Additives

2006 ◽  
Vol 45 ◽  
pp. 462-470 ◽  
Author(s):  
Eva Gregorová ◽  
W. Pabst ◽  
Jiri Štĕtina
Keyword(s):  
Shear Rate ◽  
Rheological Behavior ◽  
Viscoelastic Properties ◽  
State Of The Art ◽  
Loss Modulus ◽  
Water Systems ◽  
Gel Casting ◽  
Rotational Viscometry ◽  
Ceramic Suspensions ◽  
Starch Consolidation

An overview is given of the rheological behavior of biopolymers in aqueous suspensions and of their role in new ceramic shaping processes (starch consolidation casting and carrageenan gel casting). In particular, we give a state-of-the-art account of the viscometric behavior, measured via rotational viscometry (apparent viscosity, including its shear-rate and concentration dependence), and the viscoelastic properties characterized via oscillatory shear rheometry (storage modulus, loss modulus and phase angle, including their temperature dependence), of starch-water systems, starchcontaining alumina suspensions, carrageenan-water systems and carrageenan-containing zirconia suspensions.

Micromechanical-Rheology Model for Predicting the Complex Shear Modulus of Asphalt Mastic

2010 ◽  
Vol 168-170 ◽  
pp. 523-527 ◽  
Author(s):  
Jiu Peng Zhang ◽  
Jian Zhong Pei ◽  
Bing Gang Wang
Keyword(s):  
Shear Modulus ◽  
Viscoelastic Properties ◽  
Interactive Effect ◽  
Packing Fraction ◽  
Complex Shear Modulus ◽  
Asphalt Mastic ◽  
Complex Shear ◽  
Asphalt Mastics ◽  
Einstein Coefficient ◽  
Rheology Model

The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanical-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. The Einstein coefficient is 3.761, and the maximum volumetric packing fraction is 0.562 for the measured asphalt mastic. The predicted G* of asphalt mastics is very close to the actual value, and the relative error is not exceeding 10%. The micromechanical-rheology model can predict the complex shear modulus of the asphalt mastic from the viscoelastic property of neat asphalt, the volumetric filler effect and an interactive effect between the filler and the asphalt.

Viscoelastic Characterization of Microwave Drying Nature Rubber

2011 ◽  
Vol 291-294 ◽  
pp. 1344-1350
Author(s):  
Fu Quan Zhang ◽  
Yong Zhou Wang ◽  
Mei Chen ◽  
Mao Fang Huang
Keyword(s):  
Rheological Behavior ◽  
Viscoelastic Properties ◽  
Microwave Drying ◽  
Hot Air Drying ◽  
Air Drying ◽  
Hot Air ◽  
Drying Technology

Nature rubber (NR) is neither completely viscous nor elastic in nature, but viscoelastic in their properties. In the experiment, we used two types of equipments named rubber process analyzer (RPA) 2000 and mooney viscometer to characterize the viscoelastic properties of NR dried by microwave and hot-air, respectively. In present research, RPA tests on uncured NR dried by different methods were carried out using frequency and strain sweeps, and Mooney viscometer was detected using the big rotor at 100°C. The results showed that microwave drying has not influenced the viscoelastic properties of NR greatly, without changing the profiles of its rheological behavior. Compared with hot-air drying, the properties of NR dried by microwave improved significantly. As a new application, microwave drying technology offered an alternative way to the drying of NR.

scholarly journals Changes of Viscoelastic Properties of Aptamer-Based Sensing Layers Following Interaction with Listeria innocua

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5585
Author(s):  
Marek Tatarko ◽  
Sandro Spagnolo ◽  
Veronika Oravczová ◽  
Judit Süle ◽  
Milan Hun ◽  
...  
Keyword(s):  
Protein Structure ◽  
Shear Modulus ◽  
Resonant Frequency ◽  
Penetration Depth ◽  
Quartz Crystal Microbalance ◽  
Viscoelastic Properties ◽  
Quartz Crystal ◽  
Viscosity Coefficient ◽  
Listeria Innocua ◽  
E Coli

A multiharmonic quartz crystal microbalance (QCM) has been applied to study the viscoelastic properties of the aptamer-based sensing layers at the surface of a QCM transducer covered by neutravidin following interaction with bacteria Listeria innocua. Addition of bacteria in the concentration range 5 × 103–106 CFU/mL resulted in a decrease of resonant frequency and in an increase of dissipation. The frequency decrease has been lower than one would expect considering the dimension of the bacteria. This can be caused by lower penetration depth of the acoustics wave (approximately 120 nm) in comparison with the thickness of the bacterial layer (approximately 500 nm). Addition of E. coli at the surface of neutravidin as well as aptamer layers did not result in significant changes in frequency and dissipation. Using the Kelvin–Voight model the analysis of the viscoelastic properties of the sensing layers was performed and several parameters such as penetration depth, Γ, viscosity coefficient, η, and shear modulus, μ, were determined following various modifications of QCM transducer. The penetration depth decreased following adsorption of the neutravidin layer, which is evidence of the formation of a rigid protein structure. This value did not change significantly following adsorption of aptamers and Listeria innocua. Viscosity coefficient was higher for the neutravidin layer in comparison with the naked QCM transducer in a buffer. However, a further increase of viscosity coefficient took place following attachment of aptamers suggesting their softer structure. The interaction of Listeria innocua with the aptamer layer resulted in slight decrease of viscosity coefficient. The shearing modulus increased for the neutravidin layer and decreased following aptamer adsorption, while a slight increase of µ was observed after the addition of Listeria innocua.

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