Science topic

Rheology - Science topic

The study of the deformation and flow of matter, usually liquids or fluids, and of the plastic flow of solids. The concept covers consistency, dilatancy, liquefaction, resistance to flow, shearing, thixotrophy, and VISCOSITY.
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I have been using the ARG2 rheometer and conducting an Oscillatory amplitude using citrated whole blood. But I have never been able to get an LVR. Has anyone tried doing this and successfully had an LVR?
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Linear Viscoelastic Range in general corresponds to a low oscillation amplitude, when one is dealing with a frequency sweep rheological test. If you are working in controlled stress test, in which you specify the amplitude range of the stress amplitude, evolution of the dynamic rheological properties especially G' and G'' versus the stress amplitude allows you to determine the maximal amplitude stress under which the fluid shows a linear behavior. The range of the linear viscoelasticity corresponds to the stress amplitude range where G' and G'' remains constant. These later normaly should decrease beyond this maximal stress.
Good luck.
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In PIVLab a high resolution camera is needed to capture frames and send them to software to analyze and simulate the flow of fluids . but in cell culture it is not possible to organize a plan for online photography. and also optical microscopy is required in order to observe cells. therefore is it possible to record video or capture required frames separately by equipped optical microscope and import them later?
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Hello everyone, I'm sorry I don't have an answer (though, Mahshid, I can suggest looking into microPIV to see how the things are done there; the book called Particle image visualization by Adrian and Westerweel have a chapter on microPIV). Instead, since this thread is related to visualization, I would like to let you know that we've started a Flow visualization Stack exchange forum. That forum will also work for biologists (if, of course, biologists choose to participate on the forum). We are building a community currently. Once we have 60 people we will be allowed to proceed to a private beta version of the forum. Please join us if you are interested in flow vis and have questions to ask. Here's the link: https://area51.stackexchange.com/proposals/127312/flow-visualization?referrer=NTJlZjIyYzI3Zjk4N2I1NDZmMTJhZDUxMTViODcwMWUyNTM4OTI1YTU1OTYxN2ZkNDcwY2U2ZWI5NmU2OTY5OGhTtnNa4jEjFBFgB4o_K-u-LTdCqWX8yd8vul6HHcUb0
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I have a theoretical question about shear rheology: constant strain and frequency sweep. I can test this on a sample but I am trying to answer based on theory. If my geometry on the computer is set for cone but I use a parallel plate, how would my G' shift, will it shift up or down?
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Hi,
the two parameters that you measure are torque M and angular displacement θ. The shear stress σ and strain are given by the equations γ:
σ [Pa] =Kσ·M
γ [-] =Kγ·θ
where Kσ and Kγ are stress and strain related constants for a given geometry.
The shear modulus is then defined as:
G [Pa] = σ / γ = Kσ·M / (Kγ·θ)
For cone-plate, the constants are:
Kγ = 1/ β
Kσ = 3 / (2πR3)
β is the tip angle in radians, and R is the cone radius.
For plate-plate, the constants are:
Kγ = R / H
Kσ = 2 / (πR3)
H is the gap, and R is the plate radius.
If your cone and plate have the same radius, then the moduli readings match if
3β = 4H.
Remember that β is fixed, but H could be varied.
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Dear all!
recently i synthesized schiff base based hydrogel from gelatin-metal nanoparticle and oxidized CMC, and gelatin was stirred for 2d to stabilize the metal NP. prepared hydrogel, as i just mentioned in the last question, was tough at the begining( total consistency of hydrogel is 12%).But 2-3d later, this tough hydrogel started to be degraded showing the liquid comonent. and i tried this hydrogel with non-modified gelatin, it is stable without any shrink.Then gelatin-stirring step caused this weakness? lyophlized gelatin-metal NP particle is macroscopically weak than original gelatin, and dissolution is very quick compared with raw gelatin, even dissolvable at RT. So i suspect this difference made the result. But my hydrogel was based on the schiff base bond, not physical unfolding by heating. why is this covalent hydrogel unstable?
Second, my hydrogel had very nice adhesiveness like reported in literature, but unexpectedly, it became decreased as kept in tube at room temp. then, adhesiveness is dependent on the storage time and temp? here, adhesiveness test should be performed as soon as fabricated?
hope all genius let me understand clearly. Thanks
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Dear Sol Ju Pak, for the 1st Q you will find answer in this paper. The Schiff's base is unstable covalent bond depending on pH.
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I need to compare the gelling point of few samples using temperature ramp tests. The samples have different LVRs. That is, some have 0.1% of strain as LVR and some have less than 0.05% strain as LVR. Do I need to use the same strain to compare the gelling points of teh samples or can I use different strains (based on LVR)?
Thanks in advance.
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Hi, as long as you stay in LVR, the rheological properties are independent of the strain amplitude. This is not true once you exceed the LVR range and get into the large-amplitude oscillatory shear (LAOS). Beware that the LVR also changes with temperature. I recommend this paper:
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Hello,
Im having trouble understanding why I am seeing increases in viscosity at low frequency and high temperature for some neat polymers. Ive attached an example with neat LDPE. Temperatures 110C - 170C behave like you would expect for a polymer but a 190C and 210C, the visosity starts to increase as the frequency reduces.
We've seen this in some composites, and Ive always assumed it has to do with some rheological percolation. But here you can see we have a neat polymer with no filler material, which shouldnt have any percolation effects.
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Dear Matthew Eaton, this is attributed to the branching length and density. Please have a look at the attached file. My Regards
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Hi people I am attaching a File Please help me how do I explain this rheology Trend? What does it say?
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In the observed frequency window your molecules do not interact much and the material behaves more viscous. If you go to higher frequencies, G' and G'' approach and if you go to even higher frequencies, they'll probabely cross (G'>G''). This is related to your molecules entangling. If they are entangled, they can't react to deformation at higher frequencies as a liquid any more. The entanglements are a kind of physical crosslink at high frequencies, while at low frequencies the molecules can slide past each other.
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Acoustic Doppler Velocimetry (ADV) has been widely applied for velocity measurements for lab-scaled experiments in in-door laboratories.
It facilitated the measurement of the turbulent flows in high frequency and the three-dimensional flow velocities in broad ranges.
However, the ADVs for laboratory experiments have been discontinued by many manufacturers, such as microADV(Sontek) and Vectrino(Nortek).
The alternative types of equipment for velocity measurements could be Particle image velocimetry (PIV), Laser Doppler Velocimetry(LDV), electro-magnetic velocimetry(EMV), and propeller velocimetry(PV).
Optical velocimetry like PIV and LDV are generally expensive and difficult to maintain but provide detailed measurement results.
Other conventional velocimetry like EMV and PV need to contact the observation point in the flows, and it would provide inaccurate results compared to ADVs. It could also not be applicable for the measurement of turbulent quantities.
In current situations, I wonder what kind of velocimeters other researchers prefer for the hydraulic experiment in the lab.
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Hi we currently use UVP - Metflow Ultrasonic velocimeter profiler. They work with particles best. And works very well indeed. I do recommend. if you uses pure water (you can add a "dust" in the water or very fine particles, so the device read velocity to you).
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and how to control the time-dependency?
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Hi,
I hope someone will help me with my question.
I am working on the oscillating pendant drop method. I would like to know if the dilational elastic modulus E' and the loss modulus E" can be assimilated to the storage modulus G' and the shear loss modulus G"?
If yes, how is the conversion from mN/m to pascal made? Should I divide E' by the radius of the drop to assimilate as G' ? Are there any other size characteristics that can be used?
Are there any publications where I can find useful information on this topic?
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Thanks a lot!
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I'm currently looking at the rheological properties of the polymer Xanthan Gum. focusing on its dynamic viscosity to be more specific. I'm assessing the effects of pH (ranging from 3.6 to 5.6, 0.4 increment, total of 6 pH's) on the dynamic viscosity of xanthan gum solution (dissolving xanthan gum powder into acetic buffer with equal ionic strength, concentration is kept at 0.04%).
Firstly, my viscosity data collected shows that, as pH increases from 3.6 to 4.0 then 4.4, the viscosity increases; but as I bring up the pH from 4.4 to 4.8, 4.8 to 5.2, then lastly 5.2 to 5.6, the increasing viscosity trend plateaus and the increase in viscosity is less significant compared to the 3.6-4.4 jump. At this range, does pH has an effect on the viscosity of xanthan gum based on its molecular configuration? Though some sources states that xanthan gum's viscosity remains stable and unchanged within the range of pH 3-12 at a high concentration like 1% not 0.04%, yet some suggest pH still plays an effect, though I'm not sure how on the chemical and molecular aspect.
A possible conjecture I can think of is the xanthan gum's order-disorder and helix-coil transition is affected by protonation. In figure 2, it demonstrates how electrolytes affect the structure of the polymer; in figure 3, it shows how at a state of a helical rod and no longer a random coil, it is capable to hydrogen bonds among each other. Hence, I'm wondering of pH plays an effect on it's structural transition, such that the increased intermolecular forces at the form of a helical rod would make it more viscous in solution.
Here are the resources I have used so far:
Brunchi, CE., Bercea, M., Morariu, S. et al. Some properties of xanthan gum in aqueous solutions: effect of temperature and pH. J Polym Res 23, 123 (2016). https://doi.org/10.1007/s10965-016-1015-4
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Dear Ryan Lo, you may find various stufies on this topic. Please have a look at the following free access RG fille. My Regards
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I have a protein gel that is fibrous and I was hoping to use the angular frequency dependence to determine the gel point but that doesn't work very well as it doesn't obey a power law dependence which is a bit weird but I think makes sense due to the lack of fractal character.
Using just the tan(delta) is also problematic because despite using 0.5 C/min my gel takes longer to melt then expected so it shifted the tan(delta) point over by at least a couple degrees. ?I have confirmed transition points using other techniques and even a Tm using DSC.
When I use onset analysis I get results that look close to what I expected but I'm unsure if there's any good theoretical grounding beyond "inversion of the tangent point" which feels kind of week.
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I have not worked with fiber gel, but I think that it is fibers that prevent the use of the theory of two states in thermodynamics of small systems. I used it for the water/water phase transition in micellar surfactant solutions and determined the critical concentration of surfactant micellization. The analogy is that the curves must be S-shaped. Check out the article
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Hi,
I'm studying a styrene acrylic polymer latex with Trilon C (chelating agent DTPA Diethylenetriaminepentaacetic acid) in the formula but I am observing unexpectd effects.
When I remove Trilon C from my formula with tap water, I get a viscosity below 3000 cP, which is logical given divalent cations lower the viscosity. When I use Trilon C I usually get a viscosity around 6000 cP.
I then thought of doing an experiment with ultrapure water :
- without Trilon C I get a viscosity around 6000, which is what I want
- with Trilon C (still with ultrapure water), I get unexpectedly high viscosities
My question is thus does anyone know what can happen in that last case ? Theoritically there is (almost) nothing to chelate.
Thanks in advance, I'll take any bit of thought you can have!
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Trilon C- The active ingredient contained in the Trilon® C types is diethylenetriaminepentaacetic acid (DTPA or DTPA-H )- (a aminocarboxylic acid with 5 functional groups) or its salts. Complex formation is the most important property of trilon C types. Their ability to form water-soluble complexes with polyvalent ions (i.e calcium, magnesium, lead, copper, cadmium, zinc mercury, manganese, iron aluminum) over a wide range of pH 1 to 13.5 may explain the variation in the viscosity. Depending on types of ions are present in your system, different complexes will be formed. I think these soluble complexes will have considerable effect on viscosity. Please look in to what type of complexes are formed and how they influence the rheology of solutions. Thanks,
Dr. B R Gupta, Retd, Prof., I I T Kharagpur, India
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Is it possible to approximate/calculate the molecular weight of entanglement of a polymer experimentally by samples of M lower than Me? The usual methods include plateau modulus that requires having samples of M>Me at hand.
Thanks.
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By using the samples of lower molecular weight which is below Me it is not possible to estimate Me experimentally. However Mc values for different linear polymers can be obtained from literature and then using (Me ~ Mc/2) will give Me. However please note that Mc / Me may be higher than 2 depending on polymer.
Dr.B R Gupta
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It is my opinion that linear rheology oscillatory measurements performed with AFM may not be suitable for all viscoelastic materials/solids... whereas, different is the 'story' when performing stress-relaxation measurements with AFM... such as those reported in the following two articles:
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In this case,one ought to fix,keep constant,the distance between the filement tip of the AFM
and the surface of the viscoelastic sample in order to detect the attraction/ repulsion of the force field due to not only the applied stress and the corresponding strain but also the relaxation of the surface.
Again the above suggestion might not be suitable for all viscoelastic materials,especially if the filement tip of the AFM touches the dynamic surface during the examination
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I am looking for research articles that explain the behavior of fine particles under shear rates? Any contribution in this regard will be highly appreciated.
Thanks.
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Dear all,
I would like to know if anyone can help me on how to Calculate Phan-Thien-Tanner (PTT) constitutive model parameters from rheology experimental data. I need those parameter for an ANSYS polyflow simulation of die swell. I have experimental viscosity curve for PLA at 200C.
Thanks
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Many thanks for your kind answers!
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I need the density and viscosity of a molecular fluid under relatively high pressures, I expect something around 500 MPa. This kind of measurement is way outside my field, and I can find only very few groups who appear to be capable of it, all of which refused for technical reasons so far. Does anyone know a collaborator for high pressure rheology and/or densitometry?
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Philippe Vergne , I have contacted you directly regarding the high pressure viscosity measurement - we now have density mesurements, so only viscosity is missing.
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I am trying to do oscillatory rheology of concentrated polymer suspensions (glass microspheres with mean diameter of 6.1 micron) and slip is observed at higher frequencies above 100 rad/s. I've tried using a smaller strain of 0.3% in stead of 3% that is within the LVR of the unfilled polymer. I've seen in the literature that sandpaper can be used on a parallel plate geometry, but I am wondering how to pick an appropriate grit of sandpaper.
Should the sandpaper grit be larger than the particle filler, smaller, or as close as possible?
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Hello Derek,
These are great questions!
One answer is that the surface roughness of the geometries should be of sufficient depth (volume) to accommodate the quantity of continuous phase material that separates from the body of the sample. This then allows the geometry to grip the body of the sample and not only the slip layer.
In some materials there is a stress induced phase separation, as for instance with tomato ketchup, where the tomato fibers bend to release more juice when the test starts. These materials need very rough surfaces or even the use of a small vane tool in a large cup to test the bulk of the sample. However in other regular dispersions, such as the one you describe, the issue may be boundary concentration depletion (as described by Barnes et al, ) and the surface roughness probably only needs to be more than the particle size at a minimum to prevent slip.
One last thought is that the artifacts you are observing may not only be wall slip if you are seeing them at higher oscillatory frequencies. These tests can be challenging for the best of us, with the possibility of exceeding the Schrag "gap loading limit" of the sample in the test conditions and introducing a lot of geometry/motor inertia (which will ideally be corrected if everything is well calibrated). I attach a document that may help consider these other issues as well.
Best regards,
Phil
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I'm trying to explain a decrease in shear thinning for an anode slurry using lithiated poly(acrylic acid) and styrene butadiene rubber (SBR) as binders. Does anyone know some good literature that I could get started with?
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Hello Robert,
I don't have a list of references but it's common that such slurries age with time due to normal physical processes including:
  • Absorption of the continuous phase into the mineral or metal ion particles (would probably take up to 7 days or so depending on the viscosity, porosity and particle size)
  • Loss of volatiles over time (depending on the continuous phase and storage conditions)
  • Sedimentation - this may be unlikely if the slurry is higher in viscosity / yield stress, but possible if thinner. Would be evident from a sedimentary layer forming at the base of the container
  • Loose agglomeration of the finely dispersed particles into larger clusters (with less free surface area). This could also be syneresis if a binder is present. It looks similar to sedimentation, but there is no sedimentary layer at the bottom, and there's a clear supernatent layer on the surface of the sample.
Obviously there may be other chemical reactions occurring such as oxidation, and these could be confirmed by making DSC measurements on the sample.
I hope this helps!
Best regards,
Phil
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  • Anyone ever scaled up from Brabender twin screw extruder to a Buhler one?
  • What are the scaling constants to consider?
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About several parameters that may possibly influence extrusion of ceramic pastes, you may check answers to another question at this forum ̶ «What are the most important parameters controlling the extrusion of pastes?»: https://www.researchgate.net/post/What_are_the_most_important_parameters_controlling_the_extrusion_of_pastes
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The paste is designed to be dispensed from a syringe with a small nozzle. The paste is composed of highly viscous fluidic phase, and several types of solid spheres with different densities. The fluid phase, should evaporate as a function of temperature, or at least change its viscosity as a function of temperature (first option is preferred).
Please find attached pictures of the paste.
I was wondering if I should use Smooth-particle hydrodynamics (SPH) method?
The goal of the simulation is to simulate slump phenomena as a function of paste composition, pressure distribution, deformation analysis, non-Newtonian analysis, # of printed layers, etc..
Thanks,
Gilad
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You may want to check answers to a somewhat related question at this forum for its possible interest: «What are the most important parameters controlling the extrusion of pastes?»; https://www.researchgate.net/post/What_are_the_most_important_parameters_controlling_the_extrusion_of_pastes
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I am struggling to explain rheology data if someone could help me, I will really appreciate it.
A rotational rheometer (TA Instruments, ARES-G2) was used by a third-party institution to measure the rheology. The sample size is 2ml and it is a ceramic suspension in a solvent free polymer mixture.
The data behaves like a cross-model from 2.81/s until the power-law region and then does not go into the Newtonian state after it, rather it plunges down reaching values of 0.008 Pa-s at 281/s and further approaches to 0.0006 Pa.s at 900/s.
I have been trying to find a reason for the sudden decrease in viscosity and shear stress but I couldn't find it. Is there a viscosity model like this? Has the flow just broke down?
Furthermore, the data show negative values for viscosity and shear stress at low shear rates (0.1-0.5/s). I have discarded those values however, after these negative values till 2.8 1/s the viscosity is all over the place but seems to show overall shear thickening behavior. And after 2.8 1/s it shows Newtonian followed by power-law. I am unable to find any model to explain this behavior which includes shear thickening, Newtonian and shear-thinning region. Should I discard the values before 2.81/s for model fitting?
If someone could help me explain it, I'll really appreciate it. I can share the raw data privately.
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Hello Waqas,
The problem that you're seeing is very common with polymer flow testing and is probably that the sample is coming out of the test gap. The sample that you're measuring is then effectively air with a small amount of sample, hence the viscosity is so low.
To resolve this problem, scientists usually conduct an oscillatory frequency sweep test instead of a viscometry flow curve, as for most polymers (unless highly filled), the Cox-Merz rule holds. This Cox- Merz rule is an empirical relationship, but if applicable for your materials, is that the Shear Viscosity (complex component) in oscillation is the same as the Shear Viscosity from a viscometry test, when the angular frequency (rad/s) is the same as the shear rate (1/s) respectively.
Therefore instead of running a table of shear rates, you would run an oscillation Frequency Sweep at the needed angular velocities, (in the linear viscoelastic region of strain). You can then plot Shear viscosity complex comonent vs angular frequency to get your flow curve.
Secondly, the reason that the data is negative at the start of the test is probably residual stress in the sample from when you loaded and trimmed it. eg, if you trim the sample in a same direction that the plate rotates, the sample will be pulling forward at the very start of the test and so to achieve the lower shear rates that your test requests, it needs to push the opposite way on the geometry. This artifact should be eliminated with a thermal equilibration/relaxation step at the start or by applying a slightly negative shear (say 0.02 1/s for 5 seconds) which will amount to 10% strain which should be in the LVR of the sample.
Hope this helps,
Regards
Phil
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I have measured the rheology of my ink but mistakenly entered the plate diameter 50 cm in software while in actual it was 40 cm. So the software calculated the viscosity keeping the plate diameter 50 cm. So, how I can correct the measured data ???
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Hello Sandeep,
to correct the data for viscometry, you’d need to back calculate to the correct torque and angular velocity by dividing the stress and shear rate by the stress and strain constants that you used.
shear stress = torque x c1 [the stress constant of the tool]
shear rate = angular velocity x c2 [the strain constant of the tool]
After this you’d Calculate the true stress and strain using the right C1 and C2 factors. And then lastly calculate the viscosity from stress divided by strain.
If you were making oscillation measurements it could be difficult to calculate this true stress and strain if there was significant inertia. But theoretically it would be similar using the constitutive equations.
G’=(|stress| / |strain|) X cos phase angle
G”=(|stress| / |strain|) X sin phase angle
G*=|stress| / |strain|.
Eta*=|stress| / (|strain| x angular frequency)
hope this helps!
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Asphalt binder rheology field.
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And what about other solvents, such as 5-methyl furfural or 2-MeTHF or 2,5-dimethyl furan? Is there any literature on this?
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In Asphalt Rheology, to study the behavior of material(Bitumen) Stress relaxation tests can be conducted. On what basis the input shear strain(%) can be fixed.
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Generally the Linear Viscoelastic Region is higher for higher temperatures, but the test results should be technically the same as long as you are within the LVE region. A higher strain, that is outside the LVE would be an issue. As Johannes mentioned that he tested at 0.01, 0.1 and 1%, he got the same results and they all fall within the LVE region. You of course have to consider the limitation of your device as well. You can find the LVE for your particular material by running a simple amplitude sweep and the point where your shear modulus reduces by 95% would be the highest strain you could arrive at. So for testing, reduce this limit by 15-20% to ensure LVE region.
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Does anyone know where i can find the article "letter to the editor. The mystery of the mechanism of sharkskin - Author's response" from Journal of rheology vol 43 no 1 pp.247-52 (1999)?
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I think this is the link for your article.
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dear researchers,
I wonder if the pelofsky equation is applicable to organic and inorganic solutions can explain the relation between the viscosity and surface tension of polymeric solutions or not, if I have polystyrene dissolved in DMF can I use this equation to explain the relation between these two parameters?
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Dear Ahmed Amer Flayeh,
I have atached one article which the pelofsky equation was used for polyethylene solution. In general, it is possible to use some equation of solution for polymer solution at low concentration.
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Mine is a non-Newtonian fluid (Herschel-Bulkley rheology) and magnetic microparticles are dispersed into it. Out of the three multiphase models- Mixture, VOF and Eulerian, which is the most suitable for the flow simulations in a constricted geometry?
I am using the same inlet for both the phases and specifying microparticles as an injection in DPM module. It is a pressure inlet. Kindly suggest.
Thanking in anticipation
Aashna
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For your case, if you can safely represent your slurry as a single-phase non-Newtonian fluid and have all the relevant properties in hand, then VOF will work well for you. The two fluids will be the slurry and the other Newtonian liquid.
If you had to independently study the slurry flow, I would have suggested you to go for Mixture model in fluent. I have read one paper in which they have done so but, it was not NPs.
Regards
Aashna
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Hi all,
I'm testing the viscoelasticity of some gels with oscillatory tests (oscillation with strain sweep and frequency sweep). I am wondering what the normal force (the force that's compressing the gel, in the direction perpendicular to the oscillation) should be? Thank you!
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assuming you use a parallel plates measuring geometry, the aim of setting a normal force is to have ideal contact between sample and measuring geometry.
Therefore, it highly depends on sample properties. Both higher stiffness and slippery surface, e.g. oily or greasy, require higher normal force to maintain good contact.
However, a too high normal force will (1) squeeze the sample out of the measuring gap (will require trimming, if possible) and/or (2) will lead to an unrelaxed state of the sample, and this might also modify your measuring results.
As David Sturm mentioned, the values are typically something between 1 and 5 N (depends of course also on the plate diameter).
By the way, if your sample contains polymeric components you will observe an increase of the normal force during e.g. the frequency sweep, which is perfectly fine as it reflects the relaxation behavior of the unrelaxed sample state when measured (even if you measure within the LVE range).
Best wishes
Christopher
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dear researchers,
I prepared solutions of Polystyrene/ with different ratios of MWCNT
I dissolved ps with DMF and then added MWCNT to the solution using ultrasonication then I measured the viscosity at the constant shear rate for all the prepared solutions using Brookfield cone-plate viscometer the results showed that when increasing the MWCNT concentration will lower the solution viscosity at a constant shear rate ... I need the reasons for this behavior of MWCNT
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It work as labricant so that reduces the viscosity.
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Experimental measurements using the Planar Laser-Induced Fluorescence (PLIF) technique can provide only the concentration data from the greyscale images. However, its been stated in literature that the using the Scalar Imaging Velocimetry (SIV) technique can be used to obtain the velocity of the turbulent flow from the PLIF/LIF image. This question seeks to welcome explanations on how the to get velocity field data from scalar (Grey Value) image in fluid flow using SIV. Thank you.
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Exactly my question Cengiz Camci
I am new using this technique and would want to know how to come about with the velocity data results.
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for all the rheology researchers, my question is, how relevant is a mini slump cone (smaller than a standard 50 cent rheometer).
currently based on testing, the thickness of slumped material is roughly 3-10mm. diameters are in the range between 100-200 mm. the yield stress (measured with rheometer is in between 5-40Pa).
i am just wondering if it's worth to actually calculate yield stress based on the slump height, since the value is already small and human error will dominate for sure.
open to discussion, especially if you have had experience with mini slump cones.
thanks in advance.
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The nice thing about the mini-slump test is that it is simple, rapid, and low cost. If the sample preparation and timing are well controlled, you can obtain reproducible results and you can estimate yield stress reasonably well. You may find this study interesting:
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I have been used fly ash reinforced sisal fiber polypropylene hybrid composite and rheology results were unexpected?
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Frankly, I would expect fly ash (being mostly various oxides) to act as a granular filler - increasing surface hardness and possiblity stiffness of the polymer - rather than as a plasticizer, as it should not be able to interact in a meaningful way (e.g. produce strong hydrogen bonds) with PP.
If anything, perhaps the addition of fly ash somewhat mitigates the stiffening caused by the sizal fibres, by affecting their distribution in the polymer, but this would be just speculation.
Can you perhaps provide further information about your system and achieved results?
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How to calculate "POWER LAW" in rheology from a GRAPH of shear rate vs viscosity for cellulose nanofibrils suspensions?
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Following
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How to calculate various constants like consistency index and flow behavior index, used in the Herschel Bulky model from exp data (shear stress vs shear rate) in Origin or excel?
If I need to calculate constants and other values used in Casson fluid model, how can I calculate them using Origin or Excel?
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The excel-Solver plugin can be used to fit experimentally observed shear stress-shear rate data in any Generalised Newtonian Fluid equations (i.e. Power-law, Bingham, Cross, Carreau, Carreau-Yasuda, Meter etc.) including the Herschel–Bulkley equation.
The details of how to fit any non-linear equation using Excel-solver to obtain equations parameters can be found here.
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It's something I've seen as trial and error, but to make it a little more technical I haven't seen a route for this process. Does anyone have ideas for this route?
I'm talking about the case of rotational reometers.
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Dear Juan Fernando Hernandez, what is this unseen before finding? You forgot to mention that. My Regards
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Hi friends,
Can any one please provide some technical points on how to set up pre-stress vs time rheology analysis for hydrogels using rheometer?
I have arg2 rheometer, if any can suggest some technical parameters that I can use to set up the experiment will be useful
Thanks,
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Dear Ankit Rochani, to screen the different parameters you should first find the class to which the gel under investigation belongs. The stress-time behavior is function of concentration, pH, rotating speed, temperature,... Please check the following documents. My Regards
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I am planning to find out the rheology using cross model. But, firstly, I should generate a flow curve of polymers with the mentioned parameters and without any help of instruments (rheometer, viscometer etc) . The whole process is done through extrusion. Any help would be appreciable. Thankyou in advance
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I would use theoretical methods such as Density functional theory (DFT) or any similar techniques. For more information you may refer to the following paper:
DFT-based theoretical prediction of intrinsic viscosity of polymer solutions
DOI: 10.1080/1062936X.2018.1539035
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I have done an amplitude sweep of cell suspensions ranging from 0.01-100% strain by an Anton par interfacial rheometer. At lower strain, I am getting lower elastic modulus less than 0.001 Pa. at around 50-300% strain I am getting the higher elastic modulus than loss modulus. After 300% elastic modulus starts decreasing. Please help me to find out the physical significance of the experimental result.
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You crossed the boundary between the linear and non-linear viscoelastic region, so the value of G 'started to decrease. This is a typical situation for non-linear behavior. Interpreting the data in this area, however, is definitely more difficult than in the linear one, but presumably application of LAOS, instead of SAOS will be required for your material.
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I want to fit the creep and recovery plot for Silicon elastomer. I am not sure which model should work the best. The objective is to find recovery % and time for the sample after creep.
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It depends on what we want to achieve. If we only want to archive the data, it is enough to use two functions: one increasing and one decreasing, without inflection points meeting the boundary conditions. It will be completely different when we want to take into account the physical meaning of both phenomena. Then it's best to use mechanical models. In the extreme situation, when the number of Maxwell or Kelvin-Voigt elements tends to infinity, we get two integral equations. Solving them, and, inter alia, determining the spectra of characteristic times (ill-posed inverse problem) requires the use of an algorithm based on the Tikhonov regularization parameter.
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Hello!
I am following a reaction with cellulose during which we assume the viscosity changes. The reaction is done at 50 oC and for that we also need very good mixing. What we want to do is to have the viscosity at different times during the reaction. some issues that we have is that we can not do the rheology measurement at different temperatures since our mixture changes its rheology so fast (this is at least what we have seen so far!) also we should not have any evaporation and also to solve the mixture well we need good stirring. Do you have any suggestions on what to do? And if we want to take some offline samples will that work and what types of viscosity measurements we shall do? Thanks in advance!
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What viscosity? Hard to say. Perhaps a flow curve test will suffice, and perhaps oscillatory tests will be necessary.
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I'm trying to dissolve HA in PBS or cell media, 20 mg/ml, but gets inconsistent viscosity on my solutions. Some samples are very viscous while others are very liquid. The HA functionalized with a non-polar group. Planing to look at different parameters that might affect the result.
Can anyone share how they dissolve HA and still achieve consistent viscosity?
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Dear Philip Lifwergren
Thank you for the specifications. Mw around 150 kDa is quite low and should dissolve reasonably well.
If the problems were between batches, then I presume it was due to differences in the individual reactions. Even when repeating the same protocol, you can have slightly different results in the substitution pattern, which can translate to larger viscosity variations. Your identification of aggregation as the cause seems plausible, since aggregation properties can be very sensitive to the substitution. Did the process you describe at the end of your post (removing of aggregates) eliminate the viscosity differences?
And regarding NMR, if you use just D2O as the solvent it should be fine, but we observed problems with substitution degrees from NMR for insoluble derivatives requiring mixed deuterated solvents, as described in: https://doi.org/10.1039/C6AY03067J
Regards
Josef
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aa
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Also to consider, what do you want the PhD for? Are you wanting a career in academia or industry? What is your interest like regarding computational work? Or are you more interested in experimental work? Or a mix? A masters is obviously a shorter investment than a PhD. A Masters with no thesis is about 1 year, a MS with thesis is about 2 years. I spent time with two internships, the master's thesis and took about 3 years. Later the PhD in a different school on a different topic.
One advice I would offer is be flexible. I can say that plans never seem to work out the way you think they will. If you want the PhD then there is no guarantee it will work out as you imagine (that is not necessarily a bad thing). I once planned on getting my degree and schooling done, get a job, get married, have kids. I ended up getting married then kids, then finished my degree, and then a job. You never know what life will bring and how your research will go.
As for your topics, this is not my thesis topic, but I do like more options 3-7. However, some of the froth flotation topics could combine and work in a larger study that could come together for a PhD so if I only stuck to 3-7 I could miss a chance to work on topics that compliment and that would make a potentially more cohesive study. I did some early work with flotation so don't ignore that work as I did not call the number. If there's something you have a passion about, it might be worth trying to work that into your decision. "If you love what you do, you never work a day in your life." Having passion for whatever you choose will help you along the way because not all days will go well and sometimes you may have doubts.
Also, back to a career path, would you in the end want an industrial career or an academic one? Picking areas of research you want to grow your knowledge and expand takes time. At the same time my advisor did some work in nuclear isotopes and later worked in the pulp and paper areas of research. He did not stay in just one area but found things he was interested in and made those areas of study. If you have the foundation of how to use the scientific method you can ideally work in any field you want. Figure out your problem statement, collect information, develop models and later test them. Then come to some conclusions on that work in the end. Good luck on the start of your graduate studies. There is more than one right answer so don't go crazy over making a decision.
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I have been doing rheological studies on micellar gels. I am unable to understand the interactions that are relevant in the structure formation of such gels in the presence of a polysaccharide.
Can anybody enlighten me with what actually is going on? Also, please suggest some literature on the mechanism of structure formation in such systems.
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First what polysaccharides (there are many of them with extremely different properties, e.g. towards the formation of gels), and then at what concentration. In addition, for rheology studies, it may be necessary to use LAOS instead of SAOS. From the rheological point of view, they are soft matter systems.
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I want to change some properties of WBM like pH, salinity, density, source of water etc for a little experiment to make 5/6 mud samples so that i can recalculate the rheology , fluid model and stand pipe pressure and also want to compare with a real gas well field data for its effect analysis.
Now, how can i make these WBM samples for gas well drilling?
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Hello
Thank you for your question.
If you want to change some fluid or solid properties for certain simulation you need to:
1- define the properties you need carefully
2- write a code using any programming language
(see the fluent UDF manual for corresponding question)
3- Interpret or compile the code on fluent ansys software and setup the properties
4- Run the simulation and post-processing the results.
5- Validate the output result for more accuracy.
with my kind regards
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For example ATF (Automatic Transmission Fluid).
I have noticed in my readings that they are only limited to measuring viscosity, but I cannot find studies of its viscoelastic properties.
To my understanding an ATF this working conditions is subjected to different levels of shear rate ans temperature.
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Hi all.
I did some rheological measurements to determine the viscoelastic properties of a commercial ATF (attachments).
I see that the ATF is Newtonian up to a shear rate 10^3 s-1 (equipment limit), also, the values of the storage modulus are low.
The service conditions of an ATF are much more extreme, shear rate> 10^3 s-1 and the starting temperature can be between -30°C to 20°C and in service between 80°C to 120°C on average.
Is the limitation of measuring equipment the little interest in the viscoelastic properties of ATFs?
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Dear Researchers,
Could you recommend any program to calculate fitting between experimental data and the related model or equation? for example for rheological properties.
Regards,
Akram
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the best is sigmaplot
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For a non-isothermal compressible flow (highly viscous fluid) through a channel, I am getting spatial temperature values almost up to 10% elevated from the maximum value of temperature which has been set in the domain at the initial stage as boundary condition. Is this because of viscous dissipation which adds to the temperature or is this simply a wrong result? I am not using Boussinesq approximation in the code.
#Convection
#Thermal_Convection
#Heat_Transfer
#Viscous_Disspation
#Numerical_Methods
#Computational Fluid Dynamics
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Ahmad K. Sleiti yes the grid part is well resolved and it is independent of grid setup!
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I would like to know how to measure the Mixing index of two different types of fluids if I analyzing the whole set up under the Micro-Particle Image Velocimetry system (Micro-PIV).
1 Is it possible to analyze the image captured by the CCD camera attached to the Micro PIV system and then process the image by using the MATLAB program?
2. Is there any other possible way?
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I plan to used a Bourne reaction system or similar to study reactive mixing. I wish to vary the viscosity of the system between experiments to understand how the viscosity influences the reactive mixing. This could normally be done using different concentrations of CMC or other additive. However during the Bourne reaction systems a neutralization reaction occurs resulting in change in pH which affects many additives and alters the viscosity.
Does anyone know a compound which can be used to increase the viscosity of an aqueous solution such that the viscosity is stable over a range of pHs?
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Dear Michel, you could employ HPMC as an additive in the reactions for increasing the viscosity of the system, I'm attaching a technical brochure of one of the HPMC brand names where you could find various grades of different molecular weights. In general, HPMC is nonionic and the viscosities of their solutions are stable over a wide range of pH, in my experience pH 2-12 will not affect the solution viscosity, thus there may be a gradual loss of viscosity at higher temperatures or after long periods of standing, especially with high-viscosity solutions.
On the other hand, the hydration time of HPMC will be higher under pH less than 7, so you will have to design your experimental work to obtain the desired viscosity before running the reaction you need to perform.
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YP/PV is considered as the best indicator for mud rheology. Most of the researchers find YP/PV to report rheology and they propose if the value lies in 0.75-1 lb/ft2/cp range , their mud is good. Is there any real significance of YP/PV value as I know it is used as a cutting transportation index but is there any logical reasoning behind the proposed range?
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YP/PV values has been studied by several researchers and exact range is quite debatable however while deciding a desirable range following works are considered:
Works of Chilingarian (1983) shows, lower YP/PV ratio indicates stabilization of mud whereas, standard text of Caenn(2011) mentions higher YP/PV ratio is desirable for better hole-cleaning.
Therefore, in order to obtain an optimum value of YP/PV, a mutually conflicting decision needs to be taken as both stability in terms of deflocculated condition and hole cleaning ability is essential for mud.
Several authors have studied ideal range of YP/PV of which studies of Okrajni (1986) suggest a range of 0 - 2. Gautam et al., (2020) 1 - 2.
For further studies you can refer:
Composition and Properties of Drilling and Completion Fluids, Composition and Properties of Drilling and Completion Fluids , Caenn(2011)
The Effects of Mud Rheology on Annular Hole Cleaning in Directional Wells. Okrajni 1986
Drilling Fluid Evaluation Using Yield Point-Plastic Viscosity Correlation - Chilingarian , 1983
Optimal Synthesis, Characterization, and Performance Evaluation of High-Pressure High-Temperature Polymer-Based Drilling Fluid: The Effect of Viscoelasticity on Cutting Transport, Filtration Loss, and Lubricity , Gautam (2020)
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Hello,
I want to be able to study the droplets in oil in water and water in oil emulsions. I am setting up a small scale cosmetic lab for my learning purpose.
Can anyone suggest what magnification is required for a microscope to be able do so?
Also, is 3000rpm enough to test stability or 4000 rpm is better?
Appreciate your advice.
Thank you and looking forward
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This depends on the size of your droplets:
If u are making the droplets around 100um,100 magnification is the most suitable for u.
If the droplets are around 10 um,40 or 60 magnification is the most suitable.
While if the droplets are around 1um,u need a magnification over 1000 for sure,probably 1500 is the good. Because one of my colleague is making the droplets around 1 um,and 1000 magnification is close to the limit for a clear observation.
Best regards
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Dear all,
I am wondering if someone uses a single point or double point method to determine the intrinsic viscosity of their proteins.
These methods are usually developed for polymers and does not fit for proteins.
Could you share with me your experimence on this.
Best,
Sébastien
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I am calculating the relaxation time of a concentrated polymer solution. Based on my steady shear measurement, I used curve fitting that is based on Carreau model to obtain an estimated relaxation time. Ultimately, I am going to use the estimated relaxation time to calculate Weissenberg number. I just want to know whether my polymer flow is more elastic-dominant or inertial-dominant at a particular shear rate.
Thank you.
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You should try transient tests such creep behaviour or stress relaxation in order to get accurate values of relaxation time or its spectrum.
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Please suggest suitable rheology test method for moisture curing adhesives and silane terminated pre-polymers.
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I understand not your question
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Is anybody interested to collaborate a chapter with me entitled 'Rheology and Rheological Measurements' in an Encyclopedia of Chemical Technology? We do need to complete within a month. We can share the load by formulating the outlines. Literature is not a problem. The best person should be Chemical technology/engineering/Food Engineering background, preferably, PhD candidate or with a PhD. Please contact me with your interest and background. Please write to me only if you have already worked on rheology.
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Thanks all of you for the overwhelming responses. I find the right researcher for the chapter.
I am also revising my book on rheology 2nd edition. You can see the link, however, it is too late for the book contribution.
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I am working on a project on rheology of concrete and need to provide natural kaolinite clay and calcined kaolinite clay (metakaolin). I am looking forward to hearing more from anyone who has information and I am open to more discussions.
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Hi
You can find this kind of kaolin in Zanze company in tabriz,Iran
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If a problem in a molded product occurs, is it possible to correlate the (rotational) rheological data of that specific sample with the data obtained from the virgin granules of the materials?
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If a defect occurs in an injection molded product, it is most likely to come from either the improper properties of the selected raw material or the incorrect flow properties during the processing of the raw material. If it is a processing issue, then studying the flow properties through a capillary rheometer or using a rotational rheometer under high shear rates under identical conditions to those used for the injection molding will help in developing a correlation between the rheological properties and the defects. On the other hand, if the issue is with the properties of the selected raw material then gathering rheological data in the low shear rate range with a rotational rheometer will aid in seeing the correlation between the raw material properties and the molded product defect. A better understanding can be got through the following books:
  1. A. V. Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker Inc., New York (1996).
  2. Charles P. MacDermott and Aroon V. Shenoy, Selecting Thermoplastics for Engineering Applications, Marcel Dekker Inc., New York (1997).
In case, fillers or reinforcing fibers have been added to the raw material then the following book may help in showing how the rheology is affected by their presence.
3. Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999).
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I noticed that if I change the shearing time per point, I can get different viscosity vs. shear rate curves for the same shear thickening fluid. Why does this happen? Is it because short shearing time gives insufficient time for the fluid to respond to the shear stress? This is a rheology mystery..
In the attached image, the duration is set constant for each shear rate and the shearing time per point is 120s for the curve in grey and green, and 10s for the curve in pink. Other measurement conditions are identical.
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When the shearing occurs for a short time period at each shearing rate, the measurement is occurring in the transitional zone and not at a steady-state for each point. The short shearing time gives insufficient time for the fluid to respond. That is the reason why the data at 10s in pink is different from the data at 120s (which is 12 times longer) in grey/green.
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Dear all,
Recently i ran an oscillation test using gelatin mixed with transglutaminase (conditions were 40 degree celsius, 1 Hz oscillation frequency and 1% oscillation strain) and i realized that its storage modulus were all greater than its loss modulus throughout the 30 min run. At around 1000s however the two curves crossed but after that the storage modulus remained higher than loss modulus. What is the implication or meaning of this observation? Thanks for your kind responses :)
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Dear Justin, Yes this is possible when your material contains a type of yield stress. When the stress that you apply in your oscillatory measurement is below the yield stress you are measuring properties of the network and you will find that the storage modulus is larger than the loss, hence the material is behaving close to a solid. When the stress you apply is above the yield stress you will see a cross over and a loss modulus larger than the storage modulus, indicating a more liquid behaviour. Note that it is probably easier to determine yield stress by constant stress rotational method.
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I wonder if I can measure a single viscosity value for different solution conditions using a rotational rheometer.
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If the different solution conditions that you impose all result in solutions having Newtonian characteristics, then you can certainly measure a single viscosity for each of them. On the other hand, if the different solution conditions give solutions with non-Newtonian characteristics, then it would be difficult to stick with one single viscosity value and compare the behaviors of the various solutions. Hence, you will have to run at least one or two representative solutions over a range of shear rates at a fixed temperature to establish whether the solutions are going to be Newtonian or non-Newtonian. It is only then that you can take the decision of whether to use one single viscosity value for comparison or you need the entire rheogram. Single-point viscosity measurements are not uncommon, for example, melt-flow index is used in the polymer industry for quality control and quality assurance purposes. More details about it can be found in the book
A. V.Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker, New York (1996).
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I am using the solvatochromic shift method to calculate the ground and excited state dipole moment of a nematic liquid crystal using various solvents. The main problem is the neither the difference nor the summation of absorption and emission frequencies fall into a straight line when plotted against the solvent polarity function which consist of mainly solvent dielectric constant and refractive index. In my experiments, I have use both non-polar and polar solvents. Polar solvents amongst themselves also show no definite corelation. My question i is there any specific reason why this unusual behaviour appears?? Or will it be some experimental artifect?
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The intermolecular interaction of a molecule with a solvent can be physical (depends on the dipole moment) and chemical (hydrogen bonding, donor-acceptor interaction). Therefore, you have received inappropriate behavior. Only with physical intermolecular behavior will you get adequate behavior.
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I have synthesized my polymer, which is a 30 mer. It's in powder state after purification, and it is soluble in DMSO (tried THF, Acetonitrile, etc., it seems only DMSO with sonicating works).
My final goal is to identify if my polymer has entanglements. Based on what I've read small angle oscillatory shear could give me the necessary information I need to identify entanglements at this molecular weight of my polymer. However, I'm really short on resources, is there any book or paper you would like to recommend that explains some hands on approach on how to start? I've gathered some info on geometry and type of rheometer I want to use, however, I'm confused on sample prep., like how to turn the powder into a melt?
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So it is a polypeptide. Here is a good reference to read. Good Luck
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I am working with α -Alumina (50 vol%) + water system for extrusion. For proper dispersion, I am adding a dispersant. To increase the viscosity I am adding non-ionic polymer and in the end, I am adding salt for coagulation. But the problem is that the system is behaving as shear thickening which is unsuitable for extrusion.
Please help me to find why shear thickening is happening, is mixing playing some crucial role because I am not using the high shear mixture right now.
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The shear thickening behavior is manifested because the conditions have been made favorable for agglomeration by addition of a coagulant. With application of shear stress, agglomerating suspensions have a natural tendency to increase the size of existing agglomerates resulting in higher viscosity which is unsuitable for extrusion. You are essentially dealing with a two-phase system in which there is a dispersed phase that lives inside a suspending medium which acts as a continuous phase. Spatial arrangement and distribution, agglomeration and de-agglomeration during shear are responsible for shear-thickening and shear-thinning behavior. The basic knowledge on such type of systems can be got from the book Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999).
There is a chapter on constitutive theories and equations of suspensions where the effects of shape, concentration, dimensions, and size distributions of the particles have been discussed. When it comes to controlling the rheology of two-phase systems, mixing plays a critical role in getting the system to the desired level of viscosity and non-Newtonian flow behavior. The entire Chapter 5 in the book is dedicated to the Preparation of filled polymer systems.
In section 5.4, there is a detailed discussion on the compounding /mixing variables that affect the quality of the mix. Variables affecting compounding operations could be machine variables (mixer type, rotor geometry) or operating variables (mixing time, rotor speed, ram pressure, chamber loading, mixing temperature, order of ingredient addition). Some variables are more sensitive to changes than others. It is important to study and identify these variables and understand their sensitivity so that the compounding /mixing can be carried out under optimum conditions. The effect of each of these variables for the specific alumina filler – matrix combination needs to be understood to find the optimum conditions to achieve the proper level of dispersion and distribution of alumina in the polymer solution. The necessary hints on how to go about this can be got by reading Chapter 5 of the book.
The best way to prevent agglomeration of filler particles is by surface-modification of the filler particles. In the Table 1.12 of the book Aroon V. Shenoy, Rheology of Filled Polymer Systems, Kluwer Academic Publishers, Netherlands (1999), there are several suggested surface modifiers that could work. These would be from the categories of silanes, and titanates and their full forms are given in Table 1.8. Which one would be most effective for Al2O3 can only be worked out by some mixing experiments, which are discussed in the book. Particularly for Alumina, one could think of the zircoaluminate (CAVCO MOD APG) surface modifier as it might turn out to be very effective.
Since the interest is specifically for Extrusion, the following book may help: A. V. Shenoy and D. R. Saini, Thermoplastic Melt Rheology and Processing, Marcel Dekker Inc., New York (1996). The other papers that would be relevant to this study would be
  1. M. D. Sacks, C. S. Khadilkar, G. W. Scheiffele, A. V. Shenoy, J. H. Dow and R. S. Sheu, Dispersion and rheology in ceramic processing, Advances in Ceramics, Vol. 21, p. 495 (1987).
  2. J. H. Dow, M. D. Sacks and A. V. Shenoy, Dispersion of ceramic particles in polymer melts, Cer. Trans. (Cer. Powd. Sci. IIA), Vol.1, p. 380 (1988).
  3. J. H. Dow, M. D. Sacks and A. V. Shenoy, Dispersion of alumina particles in polyethylene melts, Cer.Trans. (Cer.Powd.SciIII.), Vol. 12, p. 431 (1990).
  4. A. V. Shenoy and D. R. Saini, Prediction of pressure losses through typical die shapes based on a simple novel approach, Polym. Plastics Tech. Eng., Vol. 23, p. 169 (1984).
  5. A. V. Shenoy, Estimation of compounding conditions and grade selections in the preparation of thermoplastic melt blends, Polym. Plastics Tech. Eng., Vol. 24, p. 27 (1985).
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I have varied the shear rate from 1s-1 to 500 s-1 and wish to study the change in Reynold's number for a juice with 18% solid concentration. How to calculate the velocity term? or can it be replaced with shear rate?
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@ Robert and Yogesh: Thank you for your inputs.
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Our edited book ‘Advances in Food Rheology and Its Applications’ (Woodhead Publishing/Elsevier) 1st Edition has well received by academicians and industries. We, the editors (Jasim Ahmed, Pawel Ptaszek, Santanu Basu), are going to revise the book for its 2nd edition. We are inviting interested researchers/academicians who are working in Advances in Food Rheology or the latest trends in Food rheology to contact me (jahmed2k@yahoo.com) with a concrete plan so we can include the new chapter/s in the revised book. Please do not contact for the basics of rheology and topics covered most of the available books in the market.
You can find the current chapters covered in the book by clicking the following link:
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Jasim,
Congratulations on taking the initiative. Fyi, if you're still looking for submissions, I would recommend adding a posting on WikiCFP (www.wikicfp.com/cfp/). It's a platform for posting/browsing academic proposals. A number of the authors I've worked with have used the site successfully to recruit prospective authors.
Lastly, if your team needs help with copyediting/proofreading prior to publication, my company would be honored to support. I’m the proud Founder and Managing Director for JournalEdit, a premium editing service. JournalEdit has been helping researchers worldwide with professional scientific editing since 2012. We have a global network of 300+ experienced scholars (PhD, MD) with expertise across medical, science, and engineering fields. All our editors are exclusively native English speakers and based in the US, UK, Canada, or Australia.
Best wishes for a smooth and successful publication journey!
Best regards,
Hamed Bazaz | Founder, Managing Director | www.journaledit.com
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Why the velocity of the spray droplets are not matching based on two diagnostics techniques (Particle image velocimetry (PIV) and Phase Doppler particle analyzer?
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PIV gives average results based on the interrogation window. PDPA gives the instantaneous velocity at a particular point. One can argue about the definition of the point mentioned here. I would say the interrogation window used for PDPA is very small compared to PIV. Moreover, PIV predicts the velocity based on successive frames which sometimes may lead to false values due to several reasons (Choice of the plane, Laser pulse width, the accuracy of cross-correlation program). IF I have to choose one, I would go for PDPA, it is far more reliable and accurate than other methods, provided the lasers are properly aligned and the experiments are performed correctly.
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This material is commonly used as rheology modifier and has wide usage in the cosmetic industry.
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Liponite is manufactured by BYK Chemicals.
They have their office in India.
BYK India Pvt Ltd
701 Vikas Center Dr. Choitram Gidwani Marg Chembur Mumbai 400 074 India
Phone +91 22 2520-4765 Fax +91 22 2520-4706
Pune Office
147, Mumbai-Pune Road Pimpri Pune 411 018 India
Phone + 91 20 6719-0719 Fax + 91 20 6719-0718
Hope this helps!!
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Nylon 6 Oligomers are not soluble in most common solvents such as THF, methanol or water. Solvents such as m-cresol and Hexafluoroisopropanol are costly and requires separate columns.HPLC-MS requires the compound to be dissolved in methanol, Acetonitrile, diluted formic acid.So, it's neither dissolved in these solvents. Rheology might be an option, but can it be used for oligomers? Suggest a method with references.
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Small angle (not so small) scattering techniques (neutrons, X-ray) are probably the more appropriate. You need to dissolve your sample in one of the solvent you mentioned but this will use much less solvent quantity than chromatography.
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I have a silicone material with the rheology data as shown in the attached image, that was performed using temperature sweep program from 45°C to 160°C.
I would like to understand why does the graph exhibits a double tan delta peak of the same material. What does a double tan delta peak mean from general materials point of view? Anybody has any hypothesis?
*repeated measurements also yield the same result.