Anomalous Rheological Behavior Research Articles

Temperature and shear dependence of rheological behavior for thermoplastic polyurethane nanocomposites with carbon nanofillers

Multi-wall carbon nanotubes (MWCNTs), graphene nanoplates (GNPs), and hybrid fillers (MWCNTs/GNPs) filled thermoplastic polyurethane (TPU) nanocomposites are prepared via melt mixing. The effects of the fillers (contents of 1, 2, and 3 wt%), shear rate, and temperature are investigated on the rheological behavior of the TPU nanocomposites. The results demonstrate that the TPU/MWCNT nanocomposites exhibit stronger polymer-filler and filler-filler interactions than the TPU/GNP and TPU/GNP/MWCNT nanocomposites, and the interactions are destroyed at higher shear rates. Anomalous rheological behavior is found in the nanocomposites with 2 and 3 wt% MWCNTs (2CNT and 3CNT) and 3 wt% MWCNTs/GNPs (3Hybrid). Specifically, as rising the temperature at higher temperatures (180–190 °C), the melt complex viscosities in the low frequency region (<0.4 rad/s) are slightly increased for the 2CNT and 3Hybrid samples, and are more increased over a broader frequency region (<10 rad/s) for the 3CNT sample. The Fourier transform infrared spectroscopy spectra demonstrate that the anomalous rheological behavior is not caused by hydrogen bonding in the TPU nanocomposites. The anomalous rheological behavior is revealed to be attributed to the fact that stronger polymer-filler and filler-filler interactions exist in the 2CNT, 3Hybrid and especially 3CNT samples, and the interactions are strengthened with rising temperature at higher temperatures. • Effect of different fillers on rheological behavior of TPU nanocomposites was investigated. • Anomalous viscosity increase with rising temperature for TPU nanocomposites was observed. • Mechanism behind anomalous rheological behavior was explored. • Stronger polymer-filler and filler-filler interactions resulted in anomalous rheological behavior.

Understanding the Mechanistic Behavior of Highly Charged Cellulose Nanofibers in Aqueous Systems

Mechanistic behavior and flow properties of cellulose nanofibers (CNFs) in aqueous systems can be described by the crowding factor and the concept of contact points, which are functions of the aspect ratio and concentration of CNF in the suspension. In this study, CNFs with a range of aspect ratio and surface charge density (380–1360 μmol/g) were used to demonstrate this methodology. It was shown that the critical networking point of the CNF suspension, determined by rheological measurements, was consistent with the gel crowding factor, which was 16. Correlated to the crowding factor, both viscosity and modulus of the systems were found to decrease by increasing the charge density of CNF, which also affected the flocculation behavior. Interestingly, an anomalous rheological behavior was observed near the overlap concentration (0.05 wt %) of CNF, at which the crowding factor was below the gel crowding factor, and the storage modulus (G′) decreased dramatically at a given frequency threshold. This behavior ...

Anomalous rheological behavior of long glass fiber reinforced polypropylene

Dynamic rheological properties of PP-based long glass fiber-reinforced thermoplastics (LFT) were investigated. Weight fractions of the glass fibers investigated in the present study ranged from 0.15 to 0.5, which are higher than those of previous studies. We observed very abnormal rheological behavior. Complex viscosity (η*) of the LFT increased with the glass fiber content up to 40 wt. %. However, the η* with a weight fraction of 0.5 is observed to be lower than that of LFT with a weight fraction of 0.4 in spite of higher glass fiber content. From various experiments, we found that this abnormal behavior is analogous to the rheological behavior of a lyotropic liquid crystalline polymer solution and concluded that the abnormal rheological behavior for the LFT is attributed to the formation of a liquid crystal- like structure at high concentrations of long glass fibers.

Anomalous rheological behavior in chemically modified TiO2 colloidal pastes prepared for flexible dye-sensitized solar cells

Binder-free titania pastes with high viscosity were developed for the preparation of electrodes for dye-sensitized solar cells on plastic substrates. The rheological behaviour of the ethanol-based titania pastes with the addition of ammonia, hydrochloric acid and water was investigated. The change in the viscosity could be correlated with the measured zeta-potential of the colloidal titania pastes. A newly developed nano-scratch test was used to evaluate the mechanical strength or the inter-particle connectivity of the titania films prepared under different conditions. Improved inter-particle connectivity and solar cell performance were found for the pastes containing acid or water, but no such improvements were seen for the pastes containing ammonia. A maximum light-to-electrical energy conversion efficiency of 4.9% (under one sun – 100 mW cm−2) was obtained for the plastic-based dye-sensitized solar cells fabricated by the modified titania pastes.

Anomalous rheological behavior of poly(1‐vinyl‐2‐pyrrolidone) and CuCl2 in solution and their interactions in solid composites

AbstractBACKGROUND: The aggregation structure of polymers in solution is an important aspect of their behavior. The interactions between metal ions and water‐soluble polymers have a significant influence on the conformation behavior of biological macromolecules, and on the ionic selectivity of cells, etc.RESULTS: The rheological behavior of poly(1‐vinyl‐2‐pyrrolidone) (PVP) and CuCl2 dispersed in N,N‐dimethylformamide was investigated using rheological techniques. Concentrated solutions containing CuCl2 exhibited a rheological behavior different from those containing other metal chlorides (LiCl, CaCl2 and CoCl2). This indicated that the variation in the aggregation state of the PVP chains with concentration of CuCl2 was different from those of PVP solutions containing Li+, Ca2+ or Co2+ ions.CONCLUSION: The interactions between PVP and CuCl2 inhibit the crystallization of CuCl2 and induce the formation of microphase separation in the system. Copyright © 2009 Society of Chemical Industry

Anomalous rheological behavior of polyethylene melts in the gross melt fracture regime in the capillary extrusion: Effect of long‐chain branching

AbstractDuring a capillary extrusion with several different polyethylenes, we observe an abnormal rheological behavior. The nominal viscosity of some polyethylene melt in the gross melt fracture regime does not change with the temperature. Several metallocene‐catalyzed linear low density polyethylene are investigated. Among them, polyethylenes, which have long‐chain branches in their main chain, show this abnormal rheological behavior. By capillary extrusion experiments with various dies of different L/D ratios, it is inferred that the abnormal rheological behavior is originated in the die land, not die entrance nor die exit. From various experiments, we notice that this abnormal phenomenon may be used to detect long‐chain branch of PE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Anomalous rheological response for binary blends of linear polyethylene and long‐chain branched polyethylene

AbstractThe rheological properties are studied for binary blends composed of a low‐density polyethylene (LDPE) and a linear polyethylene. It is found that some blends exhibit higher oscillatory shear moduli and drawdown force than the individual pure components, demonstrating that relaxation mechanism with longer characteristic time appears in the blend. The anomalous rheological behavior is detected more clearly for the blends with autoclave‐LDPE than those with tubular‐LDPE. Furthermore, the number of short‐chain branches in a linear polyethylene has no influence on the rheological properties of the blends, suggesting that the phase separation will not be responsible for the anomalous behavior. It is also found that blends of autoclave‐LDPE and tubular‐LDPE show no synergetic effect. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 26:173–181, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20100

Anomalous Rheological Behaviour of Gelatin-Carrageenan-Water System Induced by Ionizing Radiation

ABSTRACT Polysaccharide biodegradable hydrogels had been developed to be used for the controlled delivery of pharmaceutically active protein. Also, food hydrogels having biodegradability are used to prepare new materials required for packaging by the food industry. In this paper two common food hydrogels were submitted to ionizing radiation. Gelatin and carrageenan solutions alone as well as ternary water-gelatin-carrageenan systems (97.5:1.0:1.5) were 60Co-irradiated with different radiation doses (0–20 kGy). The comparison of viscosity versus dose patterns of previous and irradiated resulting systems showed an anomalous rheological behavior produced by radiation suggesting the formation of a protein–polysaccharide complex.

Anomalous rheological behavior of polyethylene melts in the gross melt fracture regime in the capillary extrusion

During the capillary extrusion with several different polyethylenes, we observe an abnormal rheological behavior. The nominal viscosity of polyethylene melt in the gross melt fracture regime does not change with a temperature. All polyethylenes tested show same behaviors. More interestingly, the nominal viscosity in the gross melt fracture regime shows even no molecular weight dependency when PEs have similar molecular structures (degree of branching and co-monomer content). From various experiments, we conclude that this abnormal phenomenon is relevant to the structural change with the melt temperature.

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

The rheological behavior of polyvinyl acetate (PVAc) in N,N′=dimethylformamide (DMF), methyl ethyl ketone (MEK), 1,2-dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), polystyrene (PS) in DMF, MEK, DCE, THF and cyclohexane (CYH), and random ethylene-vinyl acetate (EVA) copolymer in DCE, TOL, CYH with and without surfactant of Span80 and in the DCE/CYH solvent mixtures with surfactant of Span80 was examined at high dilution. It was shown that the extent and type of the upsweep or downsweep (anomalous rheological behavior) of the reduced viscosity-concentration curves of these different polymers at high dilution are markedly dependent on the dielectric constant of the solvent and the polarity of the polymer used. The experimental results indicated that the anomalous rheological behavior of EVA copolymer, widely used as a flow improver, is related to its efficiency in reducing viscosity and depressing pour point of crude oil and waxy solvents.

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

INFLUENCE OF SOLVENT AND POLYMER SORT ON ANOMALOUS RHEOLOGICAL BEHAVIOR OF POLYMER SOLUTION AT HIGH DILUTION

The rheological behavior of polyvinyl acetate (PVAc) in N,N'\|dimethylformamide (DMF), methyl ethyl ketone (MEK), 1,2\|dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), polystyrene (PS) in DMF, MEK, DCE, THF and cyclohexane (CYH), and random ethylene\|vinyl acetate (EVA) copolymer in DCE, TOL, CYH with and without surfactant of Span80 and in the DCE/CYH solvent mixtures with surfactant of Span80 was examined at high dilution. It was shown that the extent and type of the upsweep or downsweep (anomalous rheological behavior) of the reduced viscosity\|concentration curves of these different polymers at high dilution are markedly dependent on the dielectric constant of the solvent and the polarity of the polymer used. The experimental results indicated that the anomalous rheological behavior of EVA copolymer, widely used as a flow improver, is related to its efficiency in reducing viscosity and depressing pour point of crude oil and waxy solvents.

Rheological behavior of solutions of amphiphilic acrylic copolymers in mixed solvents

A descriptive model was developed, using viscometry and light scattering, that explains the anomalous rheological behavior of solutions of amphiphilic acrylic copolymers upon the addition of water. The rheological behavior can be explained by considering the relative magnitudes of three interactions : the intra- and intermolecular electrostatic interactions between the ionizable acid groups in the copolymer, the intramolecular hydrophobic interactions, and the intermolecular hydrophobic interactions. The initial addition of water enhances the ionization of the acid groups, causing the electrostatic interactions between the acid groups to dominate the other two interactions. This leads to expansion of the polymer molecules and, consequently, to a relatively constant viscosity during dilution with water. Upon attaining the maximum ionization of the acid groups on the chain, the intramolecular hydrophobic interactions dominate the electrostatic repulsion, and the chains start to contract. Further addition of water leads to aggregation of the polymer chains into large polymolecular domains, resulting in a sharp decrease in the viscosity. Intermolecular hydrophobic interactions dominate the rheological behavior in this stage of water dilution.

F49. Can the anomalous rheological behavior of human blood be exploited to evaluate biologically important materials?

F49. Can the anomalous rheological behavior of human blood be exploited to evaluate biologically important materials?

Anomalous rheological behavior of ordered phases of block copolymers. 2

Anomalous rheological behavior of ordered phases of block copolymers. 2

Anomalous rheological behavior of ordered phases of block copolymers. 1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnomalous rheological behavior of ordered phases of block copolymers. 1Takao Ohta, Yoshihisa Enomoto, James L. Harden, and Masao DoiCite this: Macromolecules 1993, 26, 18, 4928–4934Publication Date (Print):August 1, 1993Publication History Published online1 May 2002Published inissue 1 August 1993https://doi.org/10.1021/ma00070a029RIGHTS & PERMISSIONSArticle Views333Altmetric-Citations82LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (816 KB) Get e-Alerts Get e-Alerts

Dynamics and rheology of diblock copolymers quenched into microphase-separated states.

We propose a theoretical interpretation of observed anomalous rheological behavior of diblock copolymers quenched into microphase-separated states having locally lamellar morphology with disorder. The proposed mechanism of the anomaly is associated with the second-sound modes occurring in a locally lamellar structure that are overdamped in a wide wave-vector region due to large shear viscosity. The resulting complex shear modulus is proportional to (i\ensuremath{\omega}${)}^{1/2}$, which contains no adjustable parameter and is consistent with the experimental result by Bates et al. [J. Chem. Phys. 92, 6255 (1990)].

Influence of shearing history on the rheological properties and processability of branched polymers. IV. Capillary flow and die swell of low‐density polyethylene

AbstractLow‐density polyethylene (LDPE) melts show anomalous rheological behavior; their viscoelastic properties vary with their shearing histories although their molecular structural parameters do not change. Capillary flow and die swell behavior were dependent not only on the experimental conditions such as temperature or shear stress but also on the processing index (PI), which was introduced in a preceding article in order to quantify the anomalous rheological behavior of LDPE melts. In addition, it was found that the flow activation energy at constant shear stress also varied with the shearing histories. The experimental findings are discussed in terms of the rheological flow units of LDPE melts.

Clinical implications of blood rheology studies.

Blood viscosity is dependent on the shear rate at which it is measured. Reversible red cell aggregation is largely a function of fibrinogen-red cell interaction at normal hematocrits. Red cell aggregation is the basis for the anomalous rheological behavior of blood, since a considerable fraction of the shear stress applied to blood flowing at low shear rates is required to break up the aggregates accounting for the greater shear stress required to produce a given shear rate of low magnitude. Erythrocyte sedimentation rate is also a measure of red cell aggregation and has been used as an indicator of the "suspension stability" of blood. The tendency for red cell aggregation is greatest during periods of low flow states and is maximum when the blood is standing still. At such times, a certain shear stress, the yield stress, must be applied to overcome the reversible red cell-fibrinogen bond, causing the blood to "yield" or begin to flow. Manipulation of blood viscosity and yield shear stress, by hemodilution or fibrinogen dilution are readily accomplished, and experimental studies indicate that these rheological alterations have circulatory and metabolic significance.

Anomalous rheological behavior of muscle proteins

Anomalous rheological behavior of muscle proteins