Increase In Rheological Properties Research Articles

Development of a functional dulce de leche (milk jam) with prebiotic carbohydrates and Lacticaseibacillus rhamnosus GG

A functional dulce de leche (DL) was developed by incorporating prebiotic carbohydrates (inulin and maltodextrin) and probiotic Lacticaseibacillus rhamnosus ATCC 53103 (LGG) (either as free cells, or encapsulated in pectin beads with or without prebiotics). Encapsulation improved the viability of LGG cells in DL during refrigerated storage, and its survival under simulated gastrointestinal conditions. Final cell counts in all DL samples after 6 months were >106 CFU g−1. Incorporation of carbohydrates in DL and probiotic encapsulation state had no significant effect on colour (L∗a∗b∗), rheological and mechanical properties. Although encapsulation state caused a significant effect on acceptability of DL, all samples scored above the minimum acceptability level, with more than 80% of consumers acceptance. Storage time had a significant effect (only after 2–3 months) on DL properties (except b∗ and adhesiveness), causing an increase in rheological properties, a decrease in texture parameters, and a decrease in L∗ and a∗.

Rheological properties and workability of PVA fiber and nano-SiO2 modified cement-based materials

Nanoparticles and fibers are frequently applied to improve the mechanical properties and durability of cement-based materials (CBM). In this study, rheology, workability and compressive strength tests were carried out to investigate the effect of PVA fiber (PF) and nano-SiO2 (NS) on rheological properties, workability and mechanical properties of CBM. Also, the function relationships of PF/NS content with rheological and workability parameters, rheological parameters with compressive strength were established separately. In addition, the effect mechanism of PF and NS was explained in depth. Finally, the fuzzy matrix method was employed to make a comprehensive evaluation on CBM performance. The results indicated that PF had negative influence on both rheological properties and workability of CBM. Whereas, NS only exhibited an increase in rheological properties of CBM at 0.5% content and a slight improvement in workability at 1.0% content. The comprehensive performance of CBM reached the optimum with PF content of 0.6%.

Exploring the effect of block copolymer architecture and concentration on the microstructure, electrical conductivity and rheological properties of PP/PS blend nanocomposites

The interface between polymer matrices and nanofillers is critical for efficient interaction to achieve the desired final properties. In this work, block copolymers were utilized to control the interface and achieve optimum interfacial interaction. Specifically, we studied the compatibilizing effects of styrene-ethylene/butadiene-styrene (SEBS) and styrene-ethylene/propylene (SEP) block copolymers on the morphology, conductivity, and rheological properties of polypropylene-polystyrene (PP/PS) immiscible blend with 2 vol% multiwall carbon nanotube (MWCNT) at different blend compositions of PP/PS 80:20, 50:50 and 20:80.MWCNTs induced co-continuity in PP/PS blends and did not obstruct with the copolymer migration to the interface. Copolymers at the interface led to blend morphology refinement. Adding block copolymers at a relatively low concentration of 1 vol% to compatibilize the PP/PS 80:20 blend substantially increased the electrical conductivity from 5.15*10−7S/cm for the uncompatibilized blend to 1.07*10−2S/cm for the system with SEP and 1.51*10−3S/m for the SEBS system. These values for the compatibilized blends are about 4 orders of magnitude higher due to the interconnection of the droplet domains. For the PP/PS 50:50 blend, the SEBS copolymer resulted in a huge increase in conductivity at above 3 vol% concentration (conductivity increased to 3.49*10−3S/cm from 5.16*10−7S/cm). Both the conductivity and the storage modulus increased as the SEBS copolymer content was increased. For the PP/PS 20:80 blend, we observed an initial decrease in conductivity at lower copolymer concentrations (1–3 vol%) and then an increase in conductivity to values higher than the uncompatibilized system, but only at a higher copolymer concentration of 10 vol%. The triblock copolymer (SEBS), which had 60 wt% PS content, shows a more significant increase in rheological properties compared to the diblock copolymer (SEP). The morphology shows that the interaction between MWCNT and PS is stronger than the interaction between MWCNT and PP, hence there is selective localization of the nanofiller in the PS phase as predicted by Young’s equation and by molecular simulation.

Influence of Anaerobic Degradation of Organic Matter on the Rheological Properties of Cohesive Mud from Different European Ports

The presence of clay-organic flocs in cohesive mud results in a complex rheological behavior of mud, including viscoelasticity, shear-thinning, thixotropy and two-step yielding. In this study, the effect of microbial degradation of organic matter on the rheological properties of mud samples, collected from different ports, was examined. The mud samples were collected from five different European ports (Port of Antwerp (PoA), Port of Bremerhaven (PoB), Port of Emden (PoE), Port of Hamburg (PoH) and Port of Rotterdam (PoR)), displaying varying sediment properties. The rheological analysis of fresh and degraded mud samples was performed with the help of several tests, including stress ramp-up tests, amplitude sweep tests, frequency sweep tests, time-dependent tests and structural recovery tests. The results showed: (i) a significant decrease in yield stresses and complex modulus after organic matter degradation for mud samples from PoA, PoH and PoR, (ii) a negligible change in rheological properties (yield stresses, crossover amplitude and complex modulus) for mud samples from PoB, and (iii) a significant increase in rheological properties for mud samples from PoE. For time-dependent tests, mud samples from PoB showed a substantial increase in hysteresis (~50% mean value) as compared to the changes in yield stresses and crossover amplitude. The analysis of gas production during degradation of organic matter showed a (i) significant release of carbon per g dry matter for mud samples from PoA, PoH and PoR, (ii) lower carbon release per g dry matter for mud samples from PoB, and (iii) a negligible carbon release per g dry matter for mud samples from PoE, which corresponded well with the change in rheological properties.

Сomposite binders for 3d additive technologies

Introduction. In recent years, there has been an active development of 3D additive technologies. This trend could not but affect the construction industry. However, printing using plastics and other organic compounds differs significantly in its technological features from printing with building compounds. Concrete and mortars used in layer-by-layer printing must have a number of technological properties, such as sufficient viscosity for extrusion by an extruder, low mobility to maintain geometry after laying, high setting speed and strength after hardening. Currently, there are a number of compositions that meet these requirements, however, they, as a rule, are not distinguished by high strength and require a wide raw material base, which may not be available in field printing conditions. As a result, it is necessary to expand the range of building materials for 3D printing, suitable for the above criteria, as well as satisfying economic indicators.Materials and methods. Research has been carried out using physical and mechanical tests, X-ray phase analysis and electron microscopy on the effect of finely ground mineral additives on the microstructure and hardening processes of composite binders with various dosages of functional additives.Results. The results of studies on the production of composite binders for 3D additive technologies using Portland cement and man-made waste - waste of wet magnetic separation of the Stary Oskol electrometallurgical plant, modified with additives accelerators (Technonikol Master) and plasticizers (Polyplast PK-R) using mathematical planning and construction of mathematical models for composite binders with different hardening times are pesented.Conclusion. The efficiency of using the obtained composite binder has been proven, the use of which provides an increase in rheological properties, and also makes it possible to save expensive portland cement.

Effect of graphene oxide on rheology, hydration and strength development of cement paste

The aim of this paper is to investigate the effect of a well-dispersed graphene oxide (GO) on workability, rheological properties, hydration kinetics, density of hydration products, and compressive strength of cement paste. Paste mixtures were prepared with 0.42 water-to-cement ratio, and a well-dispersed GO was incorporated at contents of 0.04%, 0.15%, and 0.29%, by mass of cement. When coupled with sonication time of 48 to 56 min, the optimum active superplasticizer (SP) dosage was found to be four times that of the GO. Compared to paste made with 0.16% SP and no GO, the addition of 0.04% GO increased yield stress and viscosity coefficient values of paste, total heat of hydration at 70 h, density of hydration products at 28 d, and compressive strength at 1, 3, and 7 d. The increase in rheological properties can be caused by the reduction in free water due to water absorption by the GO, while the increase in total heat and compressive strength can be associated with the nucleation effect of the GO. However, increasing the GO content from 0 to 0.15% with the SP dosage fixed at a higher dosage of 0.6% showed no effect on hydration kinetics but reduced yield stress, viscosity coefficient, and 1-d compressive strength. This behavior was attributed to the high dosage of the SP needed for dispersing the high content of GO. The beneficial effect of using 0.15% GO was evident from the increase in compressive strength at 3 and 7 d. Overall, the addition of well-dispersed GO improved the rheological properties, hydration kinetics, density of hydrates, and compressive strength of cement paste. However, the improvement achieved with GO at early age (1 d) was hindered by the retarding effect of SP used to maintain proper dispersion.

Heat-Resistant Foam Concrete on the Basis of Two-Component Binder

The composition of dry mix on the basis of two-component cementing agent (aluminous cement and clay of the “Kustikha” field), mineral additives (a metakaolin, the RSAM sulfoaluminate modifier, waste of basalt fiber), Ufapore foamer and the accelerating and plasticizing “Citrate-T” additive is developed. When mixing “Citrate-T” additive with water at Water/Solid = 0.45–0.70, the subsequent mechanical binder and hardening of a foam mass heat-resistant foam concretes with a density of 300–650 kg/m3 are formed (depending on Water/Solid value). Foam concretes have strength on compression of 0.2–2.5 MPa before warming up when their initial strength depends on processes of hydration curing of aluminous cement that provides fixation of their porous structure. After annealing at 1000 °C foam concretes have final strength of 0.3–3.2 MPa due to processes of solid-phase agglomeration of clay with other components of dry mix at their heating. Foam concretes after annealing unlike foam concretes on the basis of a Portland cement and aluminous cement have big strength. Introduction of the accelerating and plasticizing “Citrate-T” additive into composition of the dry mix leads to an increase of rheological properties in expanded foam mass and time reduction of its drying and curing. It has been established that an essential role is played by the relation Water/Solid: at increase in the relation Water/Solid (with 0.45 to 0.70) occurs increase in volume of foam mass after a mechanical binder, and also heterogeneity of pores and their sizes increases that leads to reduction of density of foam concretes and strength on compression.

Effect of thermal aging and electrolyte on bentonite dispersions: Rheology and morphological properties

In this work, the effect of thermal aging and electrolyte on the rheological and morphological properties of bentonite dispersion was studied. Previous studies reported the effect of electrolyte concentration and thermal aging on bentonite rheological properties but detailed morphological studies of the effect of electrolyte and thermal aging of bentonite dispersion have never done before. Dynamic and steady shear rheological experiments were performed at 25 °C and data were fitted to two different models (Herschel-Bulkley and Cross models) to study the rheological behavior of thermally aged and electrolyte treated bentonite dispersions. The bentonite dispersion was thermally aged at 120 °C in the rolling oven for 24 h prior to rheological measurements. The electrolyte treated bentonite dispersion was formulated by mixing 0.1 M NaCl in bentonite dispersion with constant stirring for 24 h. It was noticed that electrolyte treated bentonite dispersions have low rheological properties (viscosity, yield stress, and gel strength) compared to the base bentonite dispersion. Thermal aging of bentonite dispersion resulted in the immense increase in rheological properties of bentonite dispersion compared to the base dispersion. XRF, XRD, and TGA were used to study the chemical composition and thermal stability of the bentonite. Scanning electron microscope (SEM) analysis and transmission electron microscope (TEM) analysis were performed to understand the effect of electrolyte and thermal aging on the morphology of bentonite dispersions. The d-spacing of bentonite platelets were calculated from XRD analysis and compared with the interlayer distance measured with TEM analysis. The morphology of electrolyte treated bentonite dispersion showed the aggregation of bentonite platelets while thermal aging resulted in flocculation of the bentonite platelets. This work will help to understand the effect of electrolyte and thermal aging on rheology and morphological properties of bentonite-based drilling fluids. The comparative study of the effect of electrolyte and thermal aging on bentonite morphological properties using SEM, XRD and TEM analysis has never studied before in the literature.

INVESTIGATION OF UNIFLOX REAGENT FOR DRILLING SIBERIAN SOLVENT SOLUTIONS

The physico-chemical properties of the Unifloc polymer sample provided by VNIIBT (Moscow) were studied. And also the influence of this powdered reagent on the basic properties of clay solutions used in the Noyabrsk oil and gas region of Western Siberia was studied. The preparation is prepared by polymerization and alkaline saponification of acrylic acid. The reagent is designed to reduce the filtration and stabilization of clay solutions for drilling wells, as well as for sedimentation of suspended particles in sedimentation tanks and water storage facilities. Reagent Uniflok 4 class, produced in the Republic of Uzbekistan. The investigated sample of Unifloc reagent results in an effective reduction of the filtration index, both artificially prepared from a benthic powder solution, and the one that was produced in the well directly when drilling a well in the November region. Acceptable concentrations of Unifloc reagent in clay solutions are in the range of 0.1-0.3 %. With a higher concentration of Unifloc reagent, clay solution thickens. When drilling a well for a conductor in the November region, the Unifloc polymer concentration can be increased to 0.3-0.5%. And to control the filtration properties of the drilling mud when drilling wells under the production column, it is sufficient to adhere to 0.1 % Unifloc. This Unifloc polymer is sensitive to salts of divalent and trivalent ions, so it is suitable for the treatment of fresh solutions alone. It should also be excluded from contact with a cement mortar containing Ca, Mg salts, since clay solution may be destroyed. The new sample of the Unifloc reagent differs from the earlier received reagent batches from Uzbekistan in the November region with higher quality. Thus, the filtration properties of drilling fluids decrease more efficiently with a lower increase in rheological properties.

Effect of carbon nanotube on PA6/ECO composites: Morphology development, rheological, and thermal properties

ABSTRACTThermoplastic elastomer (TPE) nanocomposites based on polyamide‐6 (PA6)/poly(epichlorohydrin‐co‐ethylene oxide) (ECO)/multiwall carbon nanotube (MWCNTs) were prepared by melt compounding process. Different weight ratios of ECO (20, 40, and 60 wt %) and two kinds of functionalized and non‐functionalized MWCNTs were employed to fabricate the nanocomposites. The morphological, rheological, and mechanical properties of MWCNTs‐filled PA6/ECO blends were studied. The scanning electron microscopy of PA6/ECO blends showed that the elastomer particles, ECO, are well‐dispersed within the PA6 matrix. The significant improvement in the dispersibility of the carboxylated carbon nanotubes (COOH‐MWCNTs) compared to that of non‐functionalized MWCNTs (non‐MWCNTs) was confirmed by transmission electron microscopy images. The tensile modulus of samples improved with the addition of both types of MWCNTs. However, the effect of COOH‐MWCNTs was much more pronounced in improving mechanical properties of PA6/ECO TPE nanocomposites. Crystallization results demonstrated that the MWCNTs act as a nucleation agent of the crystallization process resulted in increased crystallization temperature (Tc) in nanocomposites. Rheological characterization in the linear viscoelastic region showed that complex viscosity and a non‐terminal storage modulus significantly increased with incorporation of both types of MWCNTs particularly at low frequency region. The increase of rheological properties was more pronounced in the presence of carboxylic (COOH) functional groups, in the other words by addition of COOH‐MWCNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45977.

Influence of high mixing intensity on rheology, hydration, and microstructure of fresh state cement paste

From both the fundamental and applied points of view, there is a growing interest in characterizing the rheological properties of concentrated suspensions, such as cement paste. When a cement paste is sheared, its intrinsic network structure will respond to the shear induced stresses. The influence of mixing intensity on the rheological properties of fresh state cement paste is studied. The results showed that contrary to what is popularly believed, when subjected to a high mixing intensity, the rheological properties of cement paste can increase once a certain threshold mixing intensity is achieved. This increase in rheological properties was associated with changes in the chemical nature and physical nature of the cement pastes.

State diagrams of soy globulins

State transitions of 7S and 11S soy globulins were studied as a function of moisture by monitoring their rheological and calorimetric properties. Small-amplitude oscillatory rheometry and differential scanning calorimetry (DSC) were used to characterize their denaturation and complexing reactions within a temperature range of 40–200 °C and moisture contents of approximately 20%, 30%, and 40%. Major increases in rheological properties showed that the 7S and 11S fractions with 40% moisture underwent structure forming reactions above 70 and 100 °C, respectively, while they reacted at higher temperatures for lower moisture. DSC helped to identify the individual complexing behavior of each fraction. The above, along with the information from their glass transition, previously reported, allowed us to develop state diagrams for each protein, where glassy, rubbery, entangled polymer, reaction, and free-flow states were identified.

Gas loss during foam sheet formation

This article discusses the formation of extruded thermoplastic foam sheet due to expansion of supersaturated physical blowing agent while it exists from a high-pressure flow region into atmospheric surroundings. Swarms of tiny gas cavities of unstable nature are formed and gas diffusion virtually promotes expansion, the rate of which has a strong dependency upon degree of supersaturation. However, foam sheet cooling causes increase of rheological properties to prolong the sheet formation period, during which gas molecules close to the sheet surface tend to migrate onto the surface and evaporate away from the surface to reduce foaming efficiency. The viscoelastic “cell” growth model was modified to incorporate the gas loss from the sheet surface. Foaming efficiency appears to be dependent upon blowing agent/resin ratio, foam thickness, and nucleation density (#/cc). The simulation results predicted by the model show a good agreement with experimental data for polyethylene foam with low-percentage difluorochloromethane (HCFC-22) blowing agent. © 1996 John Wiley & Sons, Inc.

THE EFFECT OF HEAT AND SHEAR ON THE VISCOELASTIC PROPERTIES OF SOY FLOUR DOUGH

ABSTRACTThis paper is concerned with the effect of heat and shear on the rheological properties of defatted soy dispersions and doughs of 30 to 60% flour by weight. Capillary and rotary rheometers (Rheometrics Mechanical Spectrometer) were used to heat doughs up to 75° C and shear them simultaneously. In one series of experiments using a modified Instron capillary rheometer the doughs were heated to several different temperatures and then sheared. The linear viscoelastic properties of the dough which were determined by means of a plate‐plate rheometer were then compared to the fresh dough and those of a heated but nonsheared dough. In another experiment a cone‐and‐plate rheometer was used to heat and shear the dough. The linear viscoelastic response of the dough was used to monitor any changes as it was heated and sheared. It was observed that only in the higher moisture dispersions (i.e., moisture contents greater than 50%) were there any signs of an increase in rheological properties which might be associated with “cooking”. It was concluded that cooking of soy flour doughs most likely does not involve the formation of a permanent network formed by covalent chemical bonds. Hence, in extrusion cooking processes involving soy flour doughs, it may not be necessary to treat the rheological properties of the dough as a thermosetting system.