non-Newtonian Pseudoplastic Fluid Research Articles

Textural, Rheological and Sensory Properties and Oxidative Stability of Nut Spreads—A Review

Tree nuts are rich in macro and micronutrients, phytochemicals, tocopherols and phenolic compounds. The development of nut spreads would potentially increase the food uses of nuts and introduce consumers with a healthier, non-animal breakfast snack food. Nut spreads are spreadable products made from nuts that are ground into paste. Roasting and milling (particle size reduction) are two important stages for the production of nut spreads that affected the textural, rheological characteristic and overall quality of the nut spread. Textural, color, and flavor properties of nut spreads play a major role in consumer appeal, buying decisions and eventual consumption. Stability of nut spreads is influenced by its particle size. Proper combination of ingredients (nut paste, sweetener, vegetable oil and protein sources) is also required to ensure a stable nut spread product is produced. Most of the nut spreads behaved like a non-Newtonian pseudo-plastic fluid under yield stress which help the producers how to start pumping and stirring of the nut spreads. Similar to other high oil content products, nut spreads are susceptible to autoxidation. Their oxidation can be controlled by application of antioxidants, using processing techniques that minimize tocopherol and other natural antioxidant losses.

Influence of different synthesis processes on the rheology of PVAc–MMT–DOAB exfoliated nano-composite

It is very helpful to guide design production and processing conditions for polymer-based inorganic or organic nano-composites by investigating their rheology. In this study, an intercalated nano-composite of montmorillonite (MMT)-dioctadecyl dimethyl ammonium bromide (DOAB) was added and reacted with vinyl acetate (VAc) to form the exfoliated nano-composite of polyvinyl acetate (PVAc)–MMT–DOAB through five different synthesis processes. The MMT–DOAB was exfoliated into nano-particles of layers or sheets and dispersed randomly in PVAc matrix. The different synthesis processes affected the dispersion and apparent viscosity of PVAc and PVAc–MMT–DOAB. With the polymerization time shortening and the water decreasing, the dispersion got bad and the apparent viscosity increased. PVAc and PVAc–MMT–DOAB were pseudo-plastic non-Newtonian fluids and both possessed the normal stress effect (Weissenberg effect) that is also called the pole-climbing phenomenon. By the help of the apparent viscosity analyzed using the power-law function equation, Newtonian fluid flow equation and Cross-Williamson model viscous equation, the different synthesis processes and MMT–DOAB had a certain effect on the rheology of PVAc and PVAc–MMT–DOAB. With the change of different synthesis processes and the increase of MMT–DOAB content in the synthesis system, the estimated molecular weight of PVAc–MMT–DOAB was also increased accordingly.

Comparison between average shear rates in conventional bioreactor with Rushton and Elephant ear impellers

As an alternative to the Rushton turbine impeller (RT), the Elephant ear impeller (EE) has been indicated as suitable for the cultivation of shear-sensitive cells such as animal cells and filamentous fungi. In the present work the average shear rate (γɛav) was evaluated and compared in a conventional bench-scale stirred-tank bioreactor, using different impeller configurations such as the Rushton turbine and the Elephant ear turbine in the down-pumping (EEDP and up-pumping (EEUP) modes. Based on recent methodology, correlations to estimate the average shear rate (γɛav) were obtained for the different impellers according to the rotational impeller speed (N), specific air flow rate (φair), and rheological properties of non-Newtonian pseudoplastic fluids. Values of γɛav predicted by the proposed method were within the range of values calculated by the correlations found in the literature, indicating that the proposed method generates reliable values of γɛav. The γɛav values obtained for the RT and EEDP impellers increase with the increase of N and decrease with the increase of φair for all non-Newtonian fluids. In contrast, for the EEUP impeller γɛav values decrease with the increase of N and φair. The negative influence of φair in γɛav at constant agitation (N) for all impellers was attributed to the increase of the gas hold-up by the increase of φair. EE impellers generated values of γɛav lower than that observed in the system equipped with the RT impeller. EEUP was the impeller that combined good oxygen mass transfer and low shear, appropriate characteristics for its use in bioprocesses involving shear-sensitive microorganisms. The importance of the correlations developed in the present work is that they allow estimation and comparison of the shear conditions in cultures as a function of the operating conditions (N, φair), rheological properties of the fluid (K and n), and volumetric oxygen transfer coefficient (kLa) in conventional bioreactors equipped with different impeller configurations in turbulent flow regime.

Structural investigation of carboxymethyl cellulose biodeterioration by Bacillus subtilis subsp. subtilis NCIB 3610

Structural changes of carboxymethyl cellulose (CMC) during biodeterioration with Bacillus subtilis subsp. subtilis NCIB 3610 were studied with small-angle X-ray scattering (SAXS), size exclusion chromatography, and viscosity measurements. Cleavage of CMC polymers changed flow characteristics from those of non-Newtonian pseudoplastic fluid to those of Newtonian fluid. The viscosity decreased from 10 to 1.4 mPas and the concentration of reducing sugar increased by 18-fold. Upon biodeterioration the average radius of gyration decreased from 147 to 123 Å; cleaved polymer chains remained in close contact in unstirred medium as reflected by a relatively large apparent radius of gyration. However, such degraded CMC aggregates were easily dispersed with shear stress. The results suggest that biodeterioration mainly affects CMC structural features that are larger than 5 nm. Furthermore, the results also suggest that CMC metabolism and biodeterioration may be decoupled; B. subtilis subsp. subtilis NCIB 3610 produces cellulases that effectively cleave CMC but cannot efficiently utilize hydrolyzed products. There were no structural or rheological changes observed in the absence of B. subtilis subsp. subtilis NCIB 3610 growth.

Development of exfoliated nanocomposite prepared from vinyl acetate and montmorillonite

To improve the chemical, physical, mechanical and thermal properties of polyvinyl acetate (PVAc), montmorillonite (MMT) was added and polymerised with vinyl acetate to prepare an exfoliated nanocomposite of PVAc–MMT. Linear macromolecular chains of PVAc were formed between MMT layers and they exfoliated MMT into layers or sheets of nanoparticles. Both PVAc and PVAc–MMT were pseudoplastic non-Newtonian fluids, and possessed the normal stress effect (or Weissenberg effect) that was the pole climbing phenomenon. PVAc–MMT’s static tensile properties were better, and PVAc’s glass transition temperature was lowered by MMT. Both PVAc and PVAc–MMT possessed cold crystallisation, and their pyrolysis were similar, because MMT had no obvious effect on pyrolysis temperatures but mainly delayed thermal degradation processes.

Preparation and characterization of exfoliated nanocomposite prepared by vinyl acetate, montmorillonite and dioctadecyl dimethyl ammonium bromide

AbstractIn the paper, an exfoliated nano-composite was prepared by vinyl acetate (VAc), montmorillonite (MMT) and dioctadecyl dimethyl ammonium bromide (DOAB).Then it was mainly studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and static tension. Its rheology was also investigated by the power-law function equation and the Cross-Williamson model viscous equation. Results showed that the exfoliated nano-composite was obtained. Linear macromolecular chains of polyvinyl acetate (PVAc) were formed in the layers of MMT-DOAB. MMT-DOAB was exfoliated into layers or sheets of nano-particles, and randomly dispersed in the matrix of PVAc. The particle diameter of MMT-DOAB was from 25 nm to 75 nm, while PVAc’s was from 250 nm to 500 nm. They randomly dispersed together. The smaller MMT-DOAB particles were adsorbed around the bigger PVAc particles; they formed the “Strawberry” structure. In addition, PVAc and PVAc- MMT-DOAB were pseudo-plastic Non-Newtonian fluids, they all possessed the normal stress effect (or Weissenberg effect), that was the pole-climbing phenomenon. The reasonable addition of MMT-DOAB in polymerization was better but not more than 2.0 wt% of VAc.

Preparation and characterization of PVAc–NMA–MMT

To further improve and enhance the performances and properties of polyvinyl acetate (PVAc), montmorillonite (MMT) and N-hydroxymethyl acrylamide (NMA) were introduced together to polymerize with vinyl acetate (VAc). The exfoliated nanocomposite of PVAc–NMA–MMT was prepared through different synthesis precursors. Linear macromolecular chains of PVAc–NMA were formed in MMT layers. MMT was exfoliated into layers or sheets of nanoparticles and dispersed randomly in PVAc–NMA matrix. Both PVAc–NMA and MMT had small particles with a diameter of 50–100 nm. They dispersed together randomly. PVAc–NMA–MMT was a pseudo-plastic non-Newtonian fluid and possessed the normal stress effect (or Weissenberg effect from the pole-climbing phenomenon. With the change of different synthesis precursors and the increase of NMA content and MMT content in the synthesis system, the molecular weight of PVAc–NMA–MMT increased. PVAc–NMA–MMT had good dispersion, excellent storage stability and high static tensile at 6.47–6.85 MPa.

CARACTERIZACIÓN BROMATOLÓGICA, FISICOQUÍMICA MICROBIOLÓGICA Y REOLÓGICA DE LA PULPA DE BOROJÓ (Borojoa patinoi Cuatrec)

En este estudio se presenta la caracterización bromatológica, fisicoquímica, microbiológica y reológica de la pulpa fresca de borojó (Borojoa patinoi Cuatrec), que son de interés en el procesamiento industrial. Se analizaron muestras de la pulpa del fruto intacto de borojó, proveniente de la provincia de Los Ríos (Ecuador), el rendimiento de la pulpa fue del 82.3% respecto del total de la fruta. La pulpa presenta un bajo pH, y tiene niveles importantes de carbohidratos y calcio. La pulpa de borojó obtenida fue de óptima calidad microbiológica, con recuentos de microorganismos que están dentro de los rangos permitidos según la normativa. Se realizó la caracterización reológica mediante ensayos de flujo en estado estacionario y ensayos oscilatorios de la pulpa de borojó a diferentes temperaturas. La pulpa de borojó presentó un comportamiento no newtoniano de carácter pseudoplástico, con un comportamiento más elástico que viscoso similar a un gel. Los resultados de los ensayos de flujo y oscilatorios muestran que la temperatura influyó en el comportamiento reológico de la pulpa de borojó.

Emulsifying, rheological and physicochemical properties of exopolysaccharide produced by Bifidobacterium longum subsp. infantis CCUG 52486 and Bifidobacterium infantis NCIMB 702205

The rheological, emulsification and certain physicochemical properties of purified exopolysaccharides (EPS) of Bifidobacterium longum subsp. infantis CCUG 52486 and Bifidobacterium infantis NCIMB 702205 were studied and compared with those of guar gum and xanthan gum. The two strains were grown in skim milk supplemented with 1.5% (w/v) casein hydrolysate at 37°C for 24h; they both produced heteropolysaccharides with different molecular mass and composition. The carbohydrate content of both polymers was more than 92% and no protein was detected. The EPS of B. longum subsp. infantis CCUG 52486 showed highly branched entangled porous structure under scanning electron microscopy. Higher intrinsic viscosity was observed for the EPS of B. longum subsp. infantis CCUG 52486 compared to the EPS of B. infantis NCIMB 702205 and guar gum. Both polymers showed pseudoplastic non-Newtonian fluid behaviour in an aqueous solution. The EPS of B. infantis NCIMB 702205 and B. longum subsp. infantis CCUG 52486 produced more stable emulsions with orange oil, sunflower seed oil, coconut oil and xylene compared to guar and xanthan gum. The EPS of B. longum subsp. infantis CCUG 52486 is the most promising one for applications in the food industry, as it had higher intrinsic viscosity, higher apparent viscosity in aqueous solution, porous dense entangled structure and good emulsification activity.

Application of sago starch as a gelling agent in jam

The use of sago as an alternative gelling agent in the jam industry was investigated by incorporating mango fruit jam with sago starch. The physicochemical, rheological, and textural properties of mango jam with sago starch were evaluated as a function of sago starch concentration for fresh and freeze-thawed samples. The jam samples behaved as non-Newtonian pseudoplastic fluids with yield stress. The Herschel–Bulkley model described the steady-state shear rheological behavior adequately with high regression coefficients (R 2 > 0.9814). Increase in sago starch concentration was positively related to the apparent viscosity whilst temperature increase gave a reversing effect. The magnitude of storage (G′) and loss (G″) moduli increased with sago starch concentration but decreased with temperature. In terms of jam texture, the hardness and work of shear increased with sago starch concentration.

Prediction of terminal velocity of solid spheres falling through Newtonian and non-Newtonian pseudoplastic power law fluid using artificial neural network

Prediction of the terminal velocity of solid spheres falling through Newtonian and non-Newtonian fluids is required in several applications like mineral processing, oil well drilling, geothermal drilling and transportation of non-Newtonian slurries. An artificial neural network (ANN) is proposed which predicts directly the terminal velocity of solid spheres falling through Newtonian and non-Newtonian power law liquids from the knowledge of the properties of the spherical particle (density and diameter) and of the surrounding liquid (density and rheological parameters). With a combination of non-Newtonian data with Newtonian data taken from published data giving a database of 88 sets, an artificial neural network is designed. Analysis of the predictions shows that the artificial neural network could be used with good engineering accuracy to directly predict the terminal velocity of solid spheres falling through Newtonian and non-Newtonian power law liquids covering an extended range of power law values from 1.0 down to 0.06.

CFD simulation of mixing for high‐solids anaerobic digestion

A computational fluid dynamics (CFD) model that simulates mechanical mixing for high-solids anaerobic digestion was developed. Numerical simulations of mixing manure slurry which exhibits non-Newtonian pseudo-plastic fluid behavior were performed for six designs: (i) one helical ribbon impeller; (ii) one anchor impeller; (iii) one curtain-type impeller; (iv) three counterflow (CF-2) impellers; (v) two modified high solidity (MHS 3/39°) impellers; and (vi) two pitched blade turbine impellers. The CFD model was validated against measurements for mixing a Herschel-Bulkley fluid by ribbon and anchor impellers. Based on mixing time with respect to mixing energy level, three impeller types (ribbon, CF-2, and MHS 3/39°) stand out when agitating highly viscous fluids, of these mixing with two MHS 3/39° impellers requires the lowest power input to homogenize the manure slurry. A comparison of digestion material demonstrates that the mixing energy varies with manure type and total solids concentration to obtain a given mixing time. Moreover, an in-depth discussion about the CFD strategy, the influences of flow regime and impeller type on mixing characteristics, and the intrinsic relation between mixing and flow field is included.

Numerical Simulation for Heat Storage Study of the Microencapsulated Phase Change Material Slurry in a Horizontal Rectangular Enclosure

Two-dimensional numerical simulation of heat storage characteristics in a horizontal rectangular enclosure heated from below by natural convection has been investigated with the microencapsulated phase change material (PCM) slurry. Effects of PCM on heat storage and heat transfer are discussed, in which PCM slurry exhibits the pseudoplastic non-Newtonian fluid behavior and a peak value in the specific heat capacity with latent heat in phase temperature range. And their characteristics between the slurries with and without phase change of PCM are compared in the phase change temperature range. And vertical temperature distributions at the middle position are given. This paper shows streamlines and isotherms in the enclosure for phase change process.

Numerical Simulation for Heat Storage Study of the Microencapsulated Phase Change Material Slurry in a Horizontal Rectangular Enclosure

Two-dimensional numerical simulation of heat storage characteristics in a horizontal rectangular enclosure heated from below by natural convection has been investigated with the microencapsulated phase change material (PCM) slurry. Effects of PCM on heat storage and heat transfer are discussed, in which PCM slurry exhibits the pseudoplastic non-Newtonian fluid behavior and a peak value in the specific heat capacity with latent heat in phase temperature range. And their characteristics between the slurries with and without phase change of PCM are compared in the phase change temperature range. And vertical temperature distributions at the middle position are given. This paper shows streamlines and isotherms in the enclosure for phase change process.

Development of Novel Polymers prepared by vinyl acetate and N-hydroxymethyl acrylamide

To improve the chemical, physical, mechanical and thermal properties of polyvinyl acetate (PVAc), N-hydroxymethyl acrylamide (NMA) was used to polymerize with vinyl acetate (VAc). During the emulsion polymerization of VAc using polyvinyl alcohol as protective colloid and ammonium persulfate as initiator, PVAc-NMA was prepared under the conventional conditions in laboratory. In the polymers, larger PVAc-NMA particles and other smaller NMA-NMA particles randomly dispersed together. Their dispersion was good. PVAc-NMA was a pseudo-plastic non-Newtonian fluid, also possessed the normal stress effect (or Weissenberg effect), the pole-climbing phenomenon. With the change of different synthesis processes and the increase in NMA content in the synthesis system, the molecular weight of PVAc-NMA increased. NMA could lower the glass transition temperature of PVAc, and then improved PVAc’s low temperature resistance, so PVAc-NMA could be applied in more harsh or much lower temperature conditions. The static tensile of PVAc-NMA was better. PVAc and PVAc-NMA all had the cold crystallization. The pyrolysis of PVAc and PVAc-NMA was similar. It was found to consist of eight phases. NMA had no obvious effect on the pyrolysis temperature but mainly delayed the thermal degradation process.

Preparation and characterization of exfoliated nano-composite of polyvinyl acetate and montmorillonite

To improve the chemical, physical, and mechanical properties of polyvinyl acetate (PVAc), montmorillonite (MMT) was added in the synthesis of PVAc in conventional lab conditions. The final product was studied mainly by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), static tensile, and the rheology was also investigated by the power-law function equation and the Cross-Williamson model viscous equation. The exfoliated nano-composite of PVAc-MMT was obtained. Linear macromolecular chains of PVAc were formed in MMT layers. MMT was exfoliated into layers or sheets of nano-particles, and randomly dispersed in PVAc matrix. The particle diameter of MMT ranged from 50 to 100 nm, while PVAc’s ranged from 250 to 500 nm, the smaller MMT particles were adsorbed around the larger PVAc particles to form the “Strawberry” structure. In addition, PVAc and PVAc-MMT were pseudo-plastic Non-Newtonian fluids, they all possessed the normal stress effect (or Weissenberg effect), that was the pole-climbing phenomenon. Key words: Polyvinyl acetate (PVAc), montmorillonite (MMT), chemical structure, dispersion, particles, rheology, static tensile.

Numerical Simulation of Natural Convection Heat Transfer on Microencapsulated PCM Slurries

A numerical investigation on natural convection heat transfer in a 2-dimensional enclosure heated from below has been conducted with microencapsulated phase change material (PCM) slurries. The microencapsulated PCM slurry exhibits pseudoplastic non-Newtonian fluid behavior and has a peak value in the specific heat capacity. The viscosity of the slurry is assumed to follow the Ostwald-de Waele power law fluid model with the power-law index n and the consistency coefficient K. Both dynamic and heat transfer characteristics are discussed on Rayleigh-Bénard natural convection. Characteristics on natural convection heat transfer have been numerically investigated for different value of the width-height aspect ratio of the enclosure. According to the comparison of the two kinds of fluid with PCM and without PCM, the start of natural convection is earlier for the fluid with PCM.

Preparation and rheological studies on the solvent based acrylic pressure sensitive adhesives with different crosslinking density

On the basis of synthesis of a series of solvent based acrylic pressure sensitive adhesives (PSAs) with different crosslinking density, the thermal and rheological properties were characterized. T g values were increased after crosslinked with MDI, and the thermal stability was also improved. Rheological studies were performed via frequency sweep, amplitude sweep, temperature sweep patterns, respectively. The creep recovery properties were also researched. In this way, it was proved that the linear viscoelastic (LVE) range was elongated as the feeding MDI increased, the elastic modulus ( G′) of the acrylic PSAs was obviously increased after crosslinked with MDI whereas hardly making any change to the viscous modulus ( G″). In the frequency sweep pattern, the PSAs samples behave as pseudoplastic non-Newtonian fluid; and zero shear viscosity increased as the feeding MDI mass ratio was increased, after discussing the cross-over frequency (ƒ ⁎ ) and the relaxation time t R , it can be concluded that the addition of MDI would make for the improvement of the elasticity of the PSAs; in the temperature sweep pattern, it could be seen that the cross-over temperatures (where G″= G′) were 34 and 70 °C for the samples crosslinked with 0 wt% and 0.1 wt% MDI, respectively. When the mass ratio of MDI fed was higher than 0.1 wt%, even though the temperature increased to 120 °C, the samples remained elastic ( G′> G″). In the creep recovery test, it was noteworthy that as the feeding ratio of MDI was increased, the creep recovery properties of the acrylic PSAs were substantially improved. And for the same sample, as the applied constant stress increased from 200 to 1000 Pa, the recoverable proportion of the materials was principally not changed in that all the experiments were carried out within the linear viscoelastic range of the samples. And the sample crosslinked with 0.5 wt% MDI shows the highest 180° peel stress.

Phase split of nitrogen/non-Newtonian fluid two-phase flow at a micro-T-junction

An experimental investigation has been undertaken to understand the phase split of nitrogen gas/non-Newtonian liquid two-phase flow passing through a 0.5 mm T-junction that oriented horizontally. Four different liquids, including water and aqueous solutions of carboxymethyl cellulose (CMC) with different mass concentrations of 0.1, 0.2 and 0.3 wt%, were employed. Rheology experiments showed that different from water, CMC solutions in this study are pseudoplastic non-Newtonian fluid whose viscosity decreases with increasing the shear rate. The inlet flow patterns were observed to be slug flow, slug–annular flow and annular flow. The fraction of liquid taken off at the side arm for nitrogen gas/non-Newtonian liquid systems is found to be higher than that for nitrogen gas/Newtonian liquid systems in all inlet flow patterns. In addition, with increasing the pseudoplasticity of the liquid phase, the side arm liquid taken off increases, but the increasing degree varies with each flow pattern. For annular flow, the increasing degree is much greater than those for slug and slug–annular flows.

Characterization and Thermal Properties of the Microencapsulated PCM Slurry

The microencapsulated phase change material (PCM) slurry is a kind of mixture with the PCM microcapsule particles and water. The actual PCM in the microcapsule is composed of several kinds of paraffin waxes (mainly nonadecane), and the membrane is a type of melamine resin. This study is focused on preparation, characterization, and thermal properties of the microencapsulated (PCM) slurry. The microencapsulated PCM particles are prepared by in-situ polymerization method. Four different levels of mass concentration Cm of the PCM will be used such as Cm=10%, 20%, 30% and 40%, respectively. The diameter of the particles is distributed in the range of 0µm~4.5µm, and most (61%) of them occur in the range of 0.5µm~1.5µm. The average volumetric diameter of the PCM microcapsule particle is about 0.78µm. And the average membrane thickness is about 11nm.Thermal properties of the microencapsulated PCM slurry are determined using differential scanning calorimeter (DSC). From DSC analysis, the melting and freezing temperatures and the latent heats of Cm=30% are measured as 38°C and 25°C, and 37.9 kJ/kg, respectively. The rheological properties are measured by a rotating cylinder type of rheometer, which the slurry shows the pseudo plastic non-Newtonian fluid behavior with the power-law fluid index n.