			Home About us Contact

Viscosity Increase (viscosity + increase)

Distribution by Scientific Domains

Polymers and Materials Science	50%
Earth and Environmental Science	20%

Selected Abstracts

Influence of filling fat type on praline products with nougat filling

EUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 12 2007
Biljana Pajin
Abstract The aim of this research was to examine the composition and functional characteristics of three samples of commercial filling fat intended for the making of nougat fillings for confectionary products. The crystallization rate of the fats was measured under static conditions using the NMR technique and under dynamic conditions as well as using a rotational rheometer. The functional characteristics of the fats were estimated by means of sensory values of the prepared praline product. Under the static conditions, all investigated filling fats showed a fast crystallization rate (,2,4%/min). The sample with the highest lauric acid contents started to crystallize immediately (no induction period). The longest induction period was found for the sample with the lowest saturated fatty acid and trans fatty acid contents. During the crystallization under dynamic conditions, all investigated samples started to crystallize more rapidly (rapid viscosity increase) at practically the same temperature (,17,°C). Measuring solid fat content and viscosity are two approaches of determining the suitability of a filling fat to be used in pralines. Both measurements provide valuable information, and particularly viscosity build-up is very important from the view of production on factory scale. [source]

Measurement of electrical conductivity, differential scanning calorimetry and viscosity of starch and flour suspensions during gelatinisation process

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2001
Saiwarun Chaiwanichsiri
Abstract Electrical conductivity measurements were applied to analyse the gelatinisation process of 12 starch or flour suspensions. The electrical conductivity of starch suspensions was found to increase upon gelatinisation because of the release of ions from starch granules. The initiation temperature of ion release, Ti, correlated well with the onset temperature in the DSC thermogram (R,=,0.868), while the completion temperature of ion release, Tf, correlated with the temperature at the start of viscosity increase (R,=,0.865). Thus Ti and Tf corresponded to the beginning and ending temperatures of gelatinisation respectively. The electrical conductivity measurement will be used as an on-line technique to monitor the whole process of starch gelatinisation. © 2001 Society of Chemical Industry [source]

A Novel Process for Ultrasound-Induced Radical Polymerization in CO2 -Expanded Fluids

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 4 2005
Maartje F. Kemmere
Abstract Summary: A strong viscosity increase upon polymerization hinders cavitation and subsequent radical formation during an ultrasound-induced bulk polymerization. In this work, ultrasound-induced radical polymerizations of methyl methacrylate (MMA) have been performed in CO2 -expanded MMA in order to reduce the viscosity of the reaction mixture. For this purpose, the phase behavior of CO2/MMA systems has been determined. With temperature oscillation calorimetry, the influence of CO2 on the viscosity and on the reaction kinetics of ultrasound-induced polymerizations of MMA has been studied. In contrast to polymerizations in bulk, this technique shows that a low viscosity is maintained during polymerization reactions in CO2 -expanded MMA. As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO2 is applied. Moreover, the ultrasound-induced polymer scission in CO2 -expanded MMA is demonstrated, which appears to be a highly controlled process. Finally, a preliminary sustainable process design is presented for the production of 10 kg/h pure PMMA (specialty product) in CO2 -expanded MMA by ultrasound-induced initiation. Process flow diagram of the ultrasound-induced polymerization of MMA in CO2 -expanded MMA. [source]

Copolymerization of 2-Acrylamido-2-methyl-1-propanesulfonic Acid and 1-Vinylimidazole in Inverse Miniemulsion

MACROMOLECULAR REACTION ENGINEERING, Issue 2 2008
Susann Wiechers
Abstract The copolymerization behavior of the acidic monomer 2-acrylamido-2-methyl-1-propanesulfonic acid (APSA) and 1-vinylimidazole in inverse miniemulsion was studied under various conditions. Initially, different surfactants and surfactant concentrations were investigated. After determining a suitable composition of the miniemulsion, changes in the reaction behavior under different pH values and monomer feed compositions were studied. The highest polymerization rates could be produced under neutral conditions over all monomer feed ratios. The addition of acid or base to change the pH value of the monomer mixture also has influence on the polymers obtained. The thermal stability, rheological stiffness and intrinsic viscosity increase when Na-APSA is incorporated. [source]

The recovery of the shear viscosity of thermally aged bulk and ribbon glassy Pd40Cu30Ni10P20 by rapid quenching from the supercooled liquid state

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 2-3 2009
V. A. Khonik
Abstract Isochronal (= linear heating) measurements of the shear viscosity below the glass transition of bulk and ribbon glassy Pd40Cu30Ni10P20 samples differing ,104 -fold in the production quenching rates have been performed. It has been found that heating up into the supercooled liquid region followed by slow cooling leads to a significant structural relaxation-induced viscosity increase upon subsequent testing. This increase, however, is not truly irreversible and the viscosity can be fully recovered (= decreased) by fast quenching from the supercooled liquid state. The effect is nearly independent of whether ribbon or bulk samples are used despite the fact that those latter are notably denser. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Extension rheology of liquid-crystalline solution/layered silicate hybrids

POLYMER ENGINEERING & SCIENCE, Issue 4 2010
Gleb B. Vasilyev
The extension rheology of polymer/layered silicate composites based on liquid-crystalline (LC) solution of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycole (PEG) was studied. The HPC concentration was 60 wt%. Extension experiments have been carried out for materials in the different phase states. Compositions containing Na-montmorillonite (MMT) were prepared by a two-stage method. Final systems may be attributed to solutions of HPC in PEG, which intercalates into MMT galleries. The ordered domain structure of the LC matrix as well as hydrogen-bonded network between HPC and PEG molecules significantly reduce deformation at break and provide a strong nonlinear viscoelastic behavior at extension. Appearance of isotropic phase in solutions leads to a sharp drop of the elongation viscosity. The introduction of clay into LC solution only slightly affects the viscosity value but significantly suppresses the strain-hardening scale. In contrast, loading in biphasic state of HPC-PEG solution with even small amount (1 wt%) of MMT leads to the drastic viscosity increase that does not change in further growth of the filler concentration. Elastic properties of the systems under study demonstrate the similar behavior. This effect likely is caused by the interrelationship between deformability of the LC domain structure and the network strength formed by the clay particles. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source]

Micro- and macrorheological properties of polypropylene-polyoxymethylene-copolyamide mixture melts

POLYMER ENGINEERING & SCIENCE, Issue 6 2001
M. V. Tsebrenko
The influence of polyoxymethylene (POM) additives on micro- and macrorheological properties of polypropylene-copolyamide (PP/CPA) mixture melts with the PP/CPA ratios of 40/60 and 20/80 wt% was investigated. We have shown that the microrheological processes such as deformation of dispersed polymer droplets and formation of liquid polymer streams, coalescence of these streams along the longitudinal direction, migration, and fracture of the liquid streams into droplets can be controlled by addition of a third component that may interact with CPA in a specific manner. The ternary mixture melt viscosity was greater than that of the binary mixture melt viscosity. The degree of viscosity increase depended upon the composition of the binary mixture, the value of shear stress, and POM content. This dependence may be explained by formation of hydrogen bonds between POM and CPA macromolecules. The addition of POM improved the specific PP fiber formation in the matrix of CPA. The latter is valid even for a composition (PP/CPA ratio is 40/60) close to phase inversion. POM migration toward the walls of the forming die occurred in the flow of the ternary polymer mixture melts. For the purpose of realizing the specific fiber formation during the processing of the above mentioned mixtures we recommend an addition of 5% to 10% of POM. [source]

Consequences of hyperconcentrated flow for process-based soil erosion modelling on the Chinese Loess Plateau

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2006
Rudi Hessel
Abstract High sediment concentrations in runoff are a characteristic feature of the Chinese Loess Plateau, and are probably caused by factors such as the occurrence of erodible materials on steep slopes, the characteristics of the loess and the harsh climate that results in low plant cover. When sediment concentration increases, fluid density increases, viscosity increases and settling velocity decreases. These effects become increasingly important with increasing concentration and can result in flow behaviour that is quite different from that of clear water flow. Although the net effect of these changes on the flow is not always apparent, erosion models that deal with high sediment concentrations should consider such effects and could include corrections for some of these effects. A case study in a small catchment on the Loess Plateau indicated that sediment concentrations were considerable, and literature data suggested that for such sediment concentrations, corrections for settling velocity, fluid density and viscosity are needed. Furthermore, a number of corrections are necessary to be able to compare field measurements with results of soil erosion models: sediment volume should be subtracted from runoff volume and a density correction is needed to use data from a pressure transducer. For flumes that were used to measure discharge from smaller areas inside the catchment, the measured water level should be corrected by subtracting the sediment level in the flume from the water level, while the sediment volume should also be subtracted from the discharge. Finally, measured concentration should be corrected to give concentration expressed as grams per litre of clear water, since soil erosion models express sediment concentration in this way. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Subducted slabs and lateral viscosity variations: effects on the long-wavelength geoid

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009
Nicola Tosi
SUMMARY The characteristic broad local maxima exhibited by the long-wavelength geoid over subduction zones are investigated with a numerical model of mantle flow. In a spherical axisymmetric geometry, a synthetic model of buoyancy driven subduction is used to test the effects on the geoid caused by the depth of penetration of the lithosphere into the mantle, by the viscosity stratification and by lateral viscosity variations (LVV) in the lithosphere, upper and lower mantle. The presence of anomalous slab density in the lower mantle guarantees geoid amplitudes comparable with the observations, favouring the picture of slabs that penetrate the transition zone and sink into the deep mantle. The viscosity of the lower mantle controls the long-wavelength geoid to the first order, ensuring a clear positive signal when it is at least 30-times greater than the upper-mantle viscosity. The presence of LVV in the lithosphere, in the form of weak plate margins, helps to increase the contribution of the surface topography, causing a pronounced reduction of the geoid. Localized LVV associated with the cold slab play a secondary role if they are in the upper mantle. On the other hand, highly viscous slabs in the lower mantle exert a large influence on the geoid. They cause its amplitude to increase dramatically, way beyond the values typically observed over subduction zones. Long-wavelength flow becomes less vigorous as the slab viscosity increases. Deformation in the upper mantle becomes more localized and power is transferred to short wavelengths, causing the long-wavelength surface topography to diminish and the total geoid to increase. Slabs may be then weakened in the lower mantle or retain their high viscosity while other mechanisms act to lower the geoid. It is shown that a phase change from perovskite to post-perovskite above the core,mantle boundary can cause the geoid to reduce significantly, thereby helping to reconcile models and observations. [source]

Rheological behavior of highly filled ethylene propylene diene rubber compounds

POLYMER ENGINEERING & SCIENCE, Issue 5 2000
M. G. Markovic
The rheological behavior of highly filled ethylene propylene diene rubber (EPDM) compounds was studied with respect to the effect of curative system, grafted rubber, shear rate, temperature and die swell using a Monsanto Processability Tester (MPT) to gain an understanding of the molecular parameters that control the surface finish. All systems show pseudoplastic behavior. At a particular shear rate, shear viscosity increases with blend ratio. The dependence of flow behavior on extrusion velocity indicates a surface effect. The extrudate die swell and maximum recoverable deformation are related by a linear relationship, which is independent of sulfur/accelerator ratio, extrusion temperature and shear rates and blend ratio. The principal normal stress difference increases nonlinearly with shear stress. Activation energy decreases with shear rate in most cases. The faster relaxing system produces extrudate of better surface quality. [source]