1:30 pm – 6:00 pm:
(Moderators: Manojkumar Chellamuthu, Tieqi Li)-Room S320A
1:30 pm – 2:00 pm:
KEYNOTE: The Rheological Intricacies of Soft Matter
Soft matter (SM) is a common term for many viscoelastic liquids and solids such as polymers, emulsions, paints, gels, and soft glasses. SM combines viscous and elastic properties in intriguing ways. Common features are a low modulus (low complex modulus for liquid SM) and slow relaxation of stress. The internal structure typically is out of equilibrium. Most SM is very fragile. This results from SM’s low modulus, where a low stress already causes large strain and internal rupturing (yielding). Quite often, it is hard to decide whether a specific SM is a liquid or solid. This shared rheological behavior makes all kinds of SM similar in appearance, however, individual relaxation patterns and viscoelasticity in general can be vastly different between one SM and another. This is where rheology becomes interesting. Time-resolved rheological methods for SM will be introduced and an attempt will be made to classify SM in terms of their characteristic relaxation patterns. Experiments demonstrate the diversity of relaxation time spectra (relaxation patterns) in SM. Which viscoelastic material functions are most sensitive to distinguish between these classes of SM? What limitations need to be considered? Is there some in-between behavior? This will be shown with chemical gels, physical gels, colloidal glasses, molecular glass formers, and drying waterborne paint.
2:00 pm – 2:30 pm:
Effect of Salt Addition on Dynamic Mechanical Properties for Poly (Methyl Methacrylate)
Masayuki Yamaguchi, Japan Advanced Institute of Science and Technology
The effect of the addition of a metal salt compound with low molecular weight on the glass transition temperature Tg was investigated using poly(methyl methacrylate) (PMMA). Lithium trifluoromethanesulfonate was found to be miscible with PMMA and thus the blends show excellent transparency. Furthermore, the Tg shift to high temperature as well as the modulus enhancement in the glassy region were detected by the addition of the salt. The electrostatic interaction between PMMA and the salt is responsible for the phenomenon. Furthermore, it was found from the oscillatory shear modulus measurements beyond Tg that rheological terminal region is clearly detected in the blend without a secondary plateau.
2:30 pm – 3:00 pm:
Synergistic Absorption of Microwave Radiation in PVDF Hybrid Nanocomposites Containing Multi-wall Carbon Nanotubes and Ferrite Particles
Uttandaraman Sundararaj, University of Calgary
This study presents absorption driven attenuation of microwave radiation in polyvinylidene fluoride (PVDF) nanocomposites facilitated by conducting multiwall carbon nanotubes (MWNTs) and ferrite particles. Electromagnetic interference (EMI) shielding was achieved via a large dielectric loss arising from electrical conductivity (associated with networks of MWNTs) and magnetic loss stemming from ferrite particles. Two different types of ferrites (i.e., nickel ferrite and cobalt ferrite) were synthesized and employed for absorption of microwave radiation. When ferrite particles along with MWNTs were incorporated in PVDF matrix, cobalt ferrites depicted the highest shielding effectiveness. Moreover, the effect of network formation of fillers in PVDF matrix was analyzed by rheology and the correlation of rheological properties with microwave attenuation was studied. The underlying mechanism of microwave absorption in these nanocomposites was systematically assessed with the help of complex permittivity and permeability in X-band frequency, as the X-band frequency range is essential for major commercial applications.
3:00 pm – 3:30 pm:
DMA – the Other Side of Rheology
Kevin Menard, Mettler-Toledo
While dynamic testing in torsional rheometers is a well known method, the use of axial or solid state DMA is often considered more of a thermal rather than a rheological technique. DMAs like the Mettler DMA 1+ allow the testing of materials from the solid state into the melt and from the uncured liquid state to a solid. This allows a fuller range of temperatures to be covered in one scan using the shear fixtures. Examples and applications will be discussed.
3:30 pm – 4:00 pm:
Rheology as a Tool to Understand Ant-Drip Properties in Properties in Flame Retardant Polycarbonate Rheology as a Tool to Understand Anti-Drip Properties in Flame Retardant Polycarbonate Resins
Manojkumar Chellamuthu, SABIC
We have investigated the flame retardant (anti-dripping properties) of a polycarbonate resin by using a dynamic mechanical analysis. A UV curable polycarbonate resin showed a strong rubbery plateau as a function of UV dosage and the amount of UV active end group. The average storage modulus is defined in the rubbery plateau region from 160 to 190°C with average storage modulus of 9 MPa being a threshold value to achieve optimum flame rating.
4:00 pm – 4:30 pm:
Nonlinear Viscoelastic Fluid Models with Fractal Time Derivative
Donggang Yao, Georgia Institute of Technology
In this paper, we present a viscoelastic fluid formulation containing fractal time derivative. We demonstrate that the inclusion of fractality allows one to model multiscale effects of typical viscoelastic fluids, overcoming undesired stationary predictions and reducing or even eliminating multiple modes in data fitting. The linear version of the fractal model is scaled up to large deformation by incorporation of objective rotation in the constitutive formulation. The resulting model having five model parameters (one for degree of fractality, two for linear viscoelasticity, one for straining, and the last one for rotation) is able to fit startup shear viscosity of a high molecular weight polystyrene solution in high accuracy, and yet using only a single mode.
4:30 pm – 5:00 pm:
Molecular Weight Distribution Prediction of Rheology against Gel Permeation Chromatography for Film Grade Polypropylene
Hoda Bayazian, Ph.D Employee, Faculty of Mechanical Engineering, Paderborn University, Germany
General purpose isotactic polypropylene (iPP) grades are not very suitable for processing operations subjected to sever elongation flow field due to their tension thinning behavior and low melt strength of their essentially linear nature. Yet, by some modification in their structure, or even changing the shaping process design, they may be readily be used in processes such as blow molding, fiber spinning, BOPP processing, etc. In this work, suitability and molecular structure requirement of two commercial PP homo-polymer film grades for slit-die extrusion were investigated. Molecular weight distribution (MWD), as the main parameter to describe the molecular structure of a linear polymer, of these resins were evaluated through measurements of GPC and rheology. From their dynamic shear data the relaxation spectra, h(τ), were calculated from which MWD was estimated using molecular viscoelastic theories and then compared with the GPC results. Generally good agreement, but with narrower MWD rheology curves was found. Exception was observed for the grade for which rheological data predicted bimodal distribution curve comprising a small shoulder of high MW, not seen in the corresponding GPC curve. A higher value of the generalized mixing parameter than that of the double reptation model which was found for this bimodal grade was attributed to an increase in the number of entanglements and better network connectivity.
5:00 pm – 5:30 pm:
Effect of Molecular Weight on Dynamics of Linear Isotactic Polypropylene Melt at Very High Shear Rates
Martin Zatloukal, Tomas Bata University in Zlin
In this work, three isotactic linear polypropylenes, with weight average molecular weights between 56 250 – 75 850 g/mol, have been characterized at 230oC over a very wide shear rate range. A low shear rate primary Newtonian plateau, a pseudoplastic region and a well developed secondary Newtonian plateau were identified for all the polypropylene melts. Flow activation energy at low (E0) and high (Einfin) shear rates was found to be 56.590 kJ/mol and 25.204 kJ/mol, respectively. For the first time, it has been discovered that the secondary Newtonian viscosity, EtaInfin, depends linearly on the weight average molecular weight, Mw, in log-log scale as EtaInfin=1.19*10^(-6)*Mw^(1.084). The observed slope close to 1 between Einfin and Mw suggests that polymer chains in the melt are disentangled at the secondary Newtonian plateau region. This conclusion is supported by the experimental observation that the high shear rate flow activation energy Einfin for given PP melts is comparable with the flow activation energy of PP like oligomer (squalane, C30H62; 2,6,10,15,19,23-hexamethyltetracosane).
5:30 pm – 6:00 pm:
Influence of Oscillating Surfaces on the Rheological Behavior of Thermoplastic Melt
Julius Geis, TU Ilmenau
This paper deals with the behavior of thermoplastic melt, which is excited by oscillations via piezoelectric actuators. The experimental setup is designed to transmit vibrations directly into the melt. The result of this procedure is a reduced viscosity for two different thermoplastic resins of up to 23 %. Amplitude and melt temperature have little to no effect on viscosity reduction during oscillation.