Melt processing behaviour and structure development in recycled PP blends with recycled PET

Because of potential reduced cost and improved retained conductivity, high viscosity friction reducers (HVFRs) are becoming increasingly popular in hydraulic fracturing stages where linear or crosslinked guar gels are traditionally used. However, concerns remain regarding the proppant transport capability of HVFRs relative to that of traditional linear gels. To address these concerns, the proppant transport capability of a polyacrylamide-based HVFR is compared with that of linear guar at cost-parity concentrations. Correlation between the proppant transport capability and rheological properties of the fluids, including viscosity and elasticity, is also discussed. A slot flow device was used to visualize the proppant transport performance of each fluid. The fluid concentrations ranged from 2.25 to 4.5 gpt (gallons per thousand gallons) for the HVFRs and 15# to 30# (pounds per thousand gallons) for guar, which were matched to achieve cost-parity between the two classes of fluids. The proppants used were 30/50, 20/40, and 12/20 mesh sand at 2 ppg (pounds per gallon) loading. Comprehensive rheological properties of the carrier fluids were characterized under steady-state and oscillatory shear and correlated with the observed proppant transport behavior. At least two sand transport mechanisms were observable in the slot flow tests. Small sand particles remained suspended in the fluid and were transported by convection. Large sand particles settled quickly, but top layers of the settled particles crept forward at a slower speed. The HVFR showed significantly better sand transport efficiency than guar at cost-parity concentrations despite the fact that the HVFR had a lower viscosity at high shear rates. The improved sand transport performance may be attributed to two factors: first, sand particles were suspended for a longer time in the HVFR because of its elevated viscosity at lower shear rates in the center of the slot; second, the HVFR's increased elasticity in the high shear regime near the wall further enhanced sand suspension by providing an elastic lifting force to hinder sand settling. The elastic effect on sand settling is estimated to be much larger than the viscous effect for the HVFR investigated herein but is neglibile in guar. Field results validated the capability of the HVFR to carry proppants, including 20/40 mesh coarse sand, in situations where traditional slickwater FRs and linear guar gel failed. This study demonstrated that the HVFR has superior proppant transport capability, relative to guar, at cost-parity concentrations despite having lower viscosity at high shear rates. The results indicate that the proppant transport performance of fracturing fluids correlates better with their elasticity and low shear viscosity than the high shear viscosity. Additionally, the findings provide much needed proppant transport data for field engineers to make rational choices for the selection of fracturing fluids.

Melt rheological properties of the blend of isotactic polypropylene (PP) and ethylene propylene diene rubber (EPDM) at varying ratios and of the glass fiber (GF) filled PP and PP/EPDM blend by varying both GF loading and blending ratio of the polyblend matrix are studied. Rheological measurements at 220°C in shear rate range 101−104s−1 were made on a capillary rheometer. Scanning electron micrographs of the extrudates are presented to show the morphology and the alignment of the glass fibers with respect to the flow direction. Variations of pseudoplasticity index, melt viscosity, and melt elasticity with EPDM content in PP/EPDM blend, and with varying GF content at any given composition of the matrix in PP/EPDM/GF ternary system, in the studied range are presented and discussed. Resultes on melt viscosity and melt elasticity show (i) reduced effect of GF at high shear rates on these properties and (ii) upward deviation of melt viscosity versus shear rate curve at low shear rates. A change in flow behavior in presence of GF is observed around a critical shear rate 2 × 103 s−1 and is attributed to the difference of interaction of GF and the dispersed rubber droplets at high and low shear rates. Elastic recovery showed nonequilibrium behavior at low shear rates.

The sensory perceptions of sweetened, flavoured and thickened solutions prepared from xanthan, dextran, sucrose and banana flavour were evaluated and correlated to rheological parameters. The primary aim of this research was to evaluate the relevance of viscosity measured at low shear or at high shear for predicting sensory perceptions. Additionally considered were extensional viscosity estimated from filament thinning experiments and complex shear viscosity. The design of experiments included two groups of 5 samples matched at low shear rate and high shear rate, respectively. Mouthfeel perceptions were well correlated to low shear viscosity, however, including high shear viscosity or extensional viscosity as an additional model parameter improved the predictive quality of the models for thickness, stickiness and mouth coating. Stickiness and mouth coating were better correlated to extensional viscosity than low shear viscosity, although a model including both parameters predicted stickiness and mouth coating best. The complex viscosity at 100 rad/s was also highly correlated to the perception of thickness. Since correlations were not improved over steady shear parameters, complex viscosity was not considered in models based on more than one rheological parameter. Flavour was also scored during sensory evaluation and sweetness and overall flavour were highly correlated. The results of this study have highlighted that there is no single rheological parameter that will ultimately correlate to a range of mouthfeel perceptions. For certain mouth feel perceptions a model comprising shear and extensional rheological parameters will have higher predictive power than a model solely based on shear rheological parameters.

Segmental blood flow and rheological determinants in diabetic patients with peripheral occlusive arterial disease

Enhancement of flocculant-aided filtration performance of coal tailings under alternating low and high shear rates

Relationship between melt shear viscosity and molecular parameters based on high impact polystyrenes in capillary extrusion

Whole blood viscosity in microvascular angina and coronary artery disease: Significance and utility

The phase behavior of two partially miscible polymer blends in simple shear flow was monitored on-line by Raman spectroscopy and subsequently with optical light microscopy on the resulting extrudate. Emphasis was placed on investigating the phase behavior in two polymer blend systems of high and low shear viscosity as they flow through a custom built flow cell with slit conduit. Shear flows initiated from one- and two-phase temperatures were monitored in the higher viscosity blend system of poly(α-methyl styrene–co-acrylonitrile) (PαMSAN) and poly(methyl methacrylate) (PMMA). For the second lower viscosity blend of poly(styrene–co-acrylonitrile) (PSAN) and PMMA90, shear flow was conducted at one-phase temperature and various shear stresses. These blends exhibit a lower critical solution temperature (LCST). The chosen blend composition used for PαMSAN/PMMA had the widest miscibility window in view of the high viscosity of the neat polymers, while for PSAN/PMMA90 blend, a composition very close to the LCST was investigated for the shear flow effects. We observed that for a blend composition of PαMSAN/PMMA system, at small temperature gap from the quiescent cloud point curve, the morphological effects due to shear heating overrides other effects. For a lower melt viscosity blend composition of PSAN/PMMA90, shear induced demixing initially occurs at low shear rates, shear-induced mixing regime follows with increasing shear flow prior to the onset of shear heating effects that brings the material to two phase region resulting in creation of locally optically observable demixed regions where the temperature rise due to shear heating across the extrudate are at maximum.

The variation of viscosity of various polymer melts under constant shear rate conditions has been investigated using a biconical viscometer, a cone-plate viscometer, and a capillary rheometer. The validity of the biconical viscometer edge-zone correction was investigated. Comparisons between the three types of viscometer showed that sample fracture at the material boundary contributed to the decrease of viscosity with time of shearing occuring in the cone-plate viscometer. Polymer melts are subjected to hydrostatic pressure within the biconical viscometer and fracture appears to be prevented. Shear stress–shear rate–time relationships were obtained for the materials studied with the biconical viscometer at shear rates up to a few reciprocal seconds. There was good agreement with capillary data at high shear rates and cone-plate data at low shear rates. A recoverable decrease of viscosity with time of shearing was found to occur. Both the fractional decrease in viscosity and the time taken to recover the original viscosity become smaller as the temperature is increased.

The current investigations are related to presenting the characteristics of flow at very high and low shear rates along with the melting process over the geometry of Riga plate. Carreau nanofluid is most appropriate mathematical viscosity model that can deal with low and high shear rates. Transportation of energy is discussed through melting conditions, thermal radiation and viscous dissipation. In this study, electromagnetic hydrodynamic aspect of nanofluid is discussed by using electromagnetic surface (Riga plate) and this system generates Lorentz force parallel to wall that keeps its effect on velocity of nanofluid. Partial differential equations (PDEs) are moved in ordinary differential equations and numerical approach named Keller Box and Shooting scheme are exercised to fetch the numerical solution of the system. An augmentation in Q leads to an enrichment in an external magnetic field. The velocity as well as momentum boundary layer booms by the virtue of an improvement in an external magnetic field. The viscosity of the nanofluid increases by the virtue of a magnification in β. Nanofluid becomes more radiated and absorbs more heat as a result of magnification in Nr, which escalates the heat transfer rate.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Edward J. Stancik, Anne L. Hawkinson, Jan Vermant, Gerald G. Fuller; Dynamic transitions and oscillatory melting of a two-dimensional crystal subjected to shear flow. Journal of Rheology 1 January 2004; 48 (1): 159–173. https://doi.org/10.1122/1.1631425 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Society of RheologyJournal of Rheology Search Advanced Search |Citation Search

The spatial organization of particles in a colloidal gel controls the macroscopic properties, such as the rheological ones or the macroscopic gel stability. However, the suspension microstructure depends in a non-trivial manner on the colloidal interactions, the concentration and the flow history. Especially the effect of the latter is so far ill-understood and difficult to study in bulk suspensions. In the present work, well-characterized two dimensional suspensions are used to study the flow-induced structure in colloidal gels. Both a parallel band apparatus and a four roll mill are used to generate surface flows and the resulting steady state structures are analyzed using video microscopy. Because of the 2D nature of the suspensions, a high temporal and spatial resolution can be obtained, rendering the visualization for a wide range of surface coverages and flow rates possible. In this wide parameter space, two different regimes can be distinguished. At low surface coverages or high shear rates, only isolated flocs exist, whereas at high surface coverages or low shear rates, a transient network structure is encountered. In the two micro structural regimes the evolution of the characteristic length scales, the dominant orientation and anisotropy and the local aggregate or cluster densities is investigated. For individual aggregates, a simple analysis of hydrodynamic forces on the aggregates is used to evaluate the shear rate dependence of the aggregate size and aggregate density.

Influence of the first normal stress differences on model hydrophobically modified ethoxylated urethane-thickened waterborne paints brush drag

Objective This article investigates the relationship of fractional flow reserve (FFR) with whole blood viscosity (WBV) in patients who were diagnosed with chronic coronary syndrome and significant stenosis in the major coronary arteries and underwent the measurement of FFR. Material and Method In the FFR measurements performed to evaluate the severity of coronary artery stenosis, 160 patients were included in the study and divided into two groups as follows: 80 with significant stenosis and 80 with nonsignificant stenosis. WBVs at low shear rate (LSR) and high shear rate (HSR) were compared between the patients in the significant and nonsignificant coronary artery stenosis groups. Results In the group with FFR < 0.80 and significant coronary artery stenosis, WBV was significantly higher compared with the group with nonsignificant coronary artery stenosis in terms of both HSR (19.33 ± 0.84) and LSR (81.19 ± 14.20) ( p < 0.001). In the multivariate logistic regression analysis, HSR and LSR were independent predictors of significant coronary artery stenosis (HSR: odds ratio: 1.67, 95% confidence interval: 1.17-2.64; LSR: odds ratio: 2.46, 95% confidence interval: 2.19-2.78). In the receiver operating characteristic (ROC) curve analysis, when the cutoff value of WBV at LSR was taken as 79.23, it had 58.42% sensitivity and 62.13% specificity for the prediction of significant coronary artery stenosis (area under the ROC curve: 0.628, p < 0.001). Conclusion WBV, an inexpensive biomarker that can be easily calculated prior to coronary angiography, was higher in patients with functionally severe coronary artery stenosis, and thus could be a useful marker in predicting the hemodynamic severity of coronary artery stenosis in patients with chronic coronary syndrome.

Zeolites and precipitated calcium carbonate (PCC) were applied together with a vinyl acetate ethylene (VAE) emulsion to identify an alternative pigment for silica to improve runnability and develop the application technology for the VAE emulsion. The low shear and high shear viscosity of the coating color were decreased when zeolites were mixed with PCC. The coating color exhibited lower shear and higher shear viscosity when the emulsion contained VAE than when it containing poly(vinyl) alcohol. Silica with a large specific surface area and pore volume exhibited a small surface contact angle, and the coating color also showed a smaller contact angle with zeolites having a porous structure than with PCC. Silica with a large specific surface area and pore volume showed high print density. For each type of pigment, the print density of coated paper was higher when using zeolites than when using PCC. When the VAE emulsion binder was applied, the ink density decreased.