Fluidity Index Research Articles

Study of PMMA Transition Interphase by Ring-Shear Method

Abstract Polymer materials are widely used in human activities from industrial application as machine parts all the way to home appliance and in food industry. It is desirable to understand the performance of these materials in terms of mechanical properties, and this has been the focus on many research works. However, most investigations are undertaken in solid state of the polymers. This paper ventures into the unraveling of the properties of polymers in their transition from a rigid state to a rubbery pasty state. Here standard polymers were studied for selected fluidity index. The results are presented in terms of shear modulus, the conservative and dissipative modulus as a function of the temperatures. It was observed that the shear modulus had a maximum around 120-130C then decreased, whereas the conservative and dissipative modulus decreased almost linearly

BACKGROUND OF MODERN TECHNIQUES FOR LABORATORY DETERMINATION OF THE ELASTICITY MODULUS OF COHESIVE SOILS AND THEIR DESIGN CHARACTERISTICS IN THE ROAD STRUCTURE (Part 1)

According to the results of laboratory stamping tests, samples (d = 150mm; H=180mm) of bulk with soil compaction having a water saturation factor Sr≥0,85 in the range of values of fluidity index – 0,5≤lℓ≤0,25 , it is concluded that it is possible to determine practically every sample, their modulus of deformability (Епр; Ед), the calculated critical resistance – Ro of soil and its maximum relative deformation λmax. The loading of the samples is carried out by a step load with a proportional (1.3 times) increased pressure, such as at each stage. During the test, the sample is not unloaded but is subject to conditional destruction, that is, a disproportionate increase in the deposits of the die. The duration of each load is three minutes. The graphs of parabolic functions of the type λ=aσb are plotted in logarithmic coordinates in the form of two segments straight on both sides of the fracture. The parameter of the degree of parabola “b” serves for preliminary estimation of the index of deformability: for the modulus of elasticity – b≈1,0 ± 0,2; for the modulus of deformation – b≈2,0 ± 0,5; for the yield modulus – b≥3.0. The work gives a comparison with similar indicators of deformability of other building and structural materials. The elastic modulus (Епр) has only a soil that meets the conditions of the standard seal ρdmax>ρdωρ і ωo<ωρ; the modulus of deformation (Ед) has a soil when 0<lℓ<0,5, and the modulus of fluidity (Ет) has only a soil lℓ≥0,5. Natural structured soils are characterized by a modulus of structural strength (Est) in the range 0<lℓ< 0, which is determined by compression tests. In order to reduce soil consumption and increase productivity, it is proposed to consider the task of determining soil deformability indices for the calculation of road clothing as a contact and therefore reduce the height of soil samples from 180 mm to 40 mm Keywords: soil, soil engineering structure, compacted soil, design condition, elastic modulus, critical design resistance, maximum relative deformation.

Airborne Survival of Escherichia coli under Different Culture Conditions in Synthetic Wastewater.

Bioaerosol generated in wastewater treatment plants has potential to harm human health. Survival of bacteria in bioaerosol during suspension is one of the major factors that affect its biological risk. It is hypothesized that bacteria grown in different wastewater have different physiology and lead to variation in airborne survival. This study investigated the relationship between the cultured conditions and the bioaerosol survival. Synthetic wastewater was used as the culture medium to simulate the water quality of wastewater. Escherichia coli BW25113 were cultured in different conditions, including growth salinity, growth temperature, growth pH, and presence of pesticide. The fatty acid composition and the reduction in airborne survival of the E. coli cultured under these conditions were determined and compared. Results showed that increasing growth salinity and temperature led to a lower reduction in airborne survival of E. coli. E. coli cultured at pH 6 had a higher reduction in airborne survival than those cultured at pH 7 and 8. Moreover, a correlation was observed between the membrane fluidity (fluidity index) and the reduction airborne survival for both aerosolization and airborne suspension. A link between culture conditions, bacterial membrane fluidity, and airborne survival was established. Culture conditions (wastewater quality) that lead to a low membrane fluidity of bacteria increase the airborne survival of bioaerosol, and vice versa. This provides a new aspect to evaluate bioaerosol survival and improve assessment on biological risk of bioaerosols.

Motor adjustments during time-constrained sit-to-walk in people with Parkinson's disease

Sit-to-walk (STW) is a sequential task and a merge of sit-to-stand (STS) and gait initiation that are impaired in people with Parkinson's disease (PD). Performing sequential task under time constraint (e.g., stand up and walk to answer an urgent call) might influence people with PD due to their deficits on internal regulation of continuous, rhythmic and fast movements. It is known the PD behavior during STS and gait initiation tasks are impaired, however, little is known regarding PD behavior on STW. Thus, the aim of this study was to assess the motor behavior of people with PD and healthy older adults during the STW task under time constraint. Fourteen people with idiopathic PD and 14 healthy older adults (OA) participated in this study. They performed the STW task under a time constraint. STW performance (STW total duration, duration of each of the 4 phases of the STW, and the drop in the center of mass (COM) momentum, identified as Fluidity Index - FI), kinematics and kinetics outcomes were assessed throughout the task. The PD group showed increased STW total time and lower FI, longer seat-off (Phase 1) time and first step (Phase 4) when compared to the OA group. Furthermore, the PD group showed more motor impairments (kinematics and kinetics) than the OA group throughout the task from seat-off until heel-off. Also, people with PD exhibited larger mediolateral COM displacement in the standing phase (Phase 2) and greater ground reaction force (GRF) in Phases 1 and 3. We observed that people with PD exhibited more restrictions when compared with healthy older adults on their STW performance, COM and GRF parameters during the STW under time constraint. Some clinical impairments usually observed in people with PD might explain their STW performance such as, motor planning deficits, less automatic motor control and mediolateral balance impairments.

Rheological study on influence of hydroxypropyl derivatives of guar gum, cellulose, and chitosan on the properties of natural hydraulic lime pastes

Viscosity enhancing admixtures are widely used to improve properties of concrete and ready-mix mortars. Guar gum derivatives and chitosan ethers are reported to have water-retaining effect, which is beneficial for the adhesion of the mixture as well as for the hydratation of hydraulic particles in the binder phase of concrete or natural hydraulic lime (NHL) mortars. Influence of addition of admixtures in doses of 1, 5, and 10‰ of the binder weight has been studied on NHL based pastes with constant water:binder ratio. The measurements were carried out on the Discovery HR-1 rheometer with DIN concentric cylinders geometry. The flow properties and viscoelastic properties were studied on the specified mixtures. Pastes expressed shear-thinning behaviour with thixotropic character of flow curves. Admixture addition caused increase of yield stress, fluidity index and consistency coefficient varying on the amount and type of the admixture. Differences in the effectivity of admixtures were observed, the dosage-dependency of the admixtures varied.

Study of thermal and rheological properties of PLA loaded with carbon and halloysite nanotubes for additive manufacturing

Purpose This paper aims to propose using polylactic acid (PLA) as an alternative to nanocomposites in additive manufacturing processes in fusion deposition modelling (FDM) systems and describe its thermal and rheological conditions with multi-wall carbon nanotube (PLA/MWCNT) and halloysite nanotube (PLA/HNT) composites for possible applications in additive manufacturing processes. Design/methodology/approach PLA/MWCNTs and PLA/HNTs were obtained through fusion in a co-rotating twin-screw extruder. PLA was mixed with different percentages of MWCNTs and HNTs at concentrations of 0.5 Wt.%, 0.75 Wt.% and 1 Wt.%. Differential scanning calorimetry (DSC) and capillary rheometry were used to characterise these products, together with an analysis of the melt flow index (MFI). Findings The DSC data revealed that the nanocomposites had a glass transition temperature Tg = 65 ± 2°C and a melting temperature Tm = 169 ± 1°C. The crystallisation temperature of PLA/MWCNTs and PLA/HNTs was between 107 ± 2°C and 129°C, respectively. The viscosity data of PLA/MWCNTs and PLA/HNTs obtained by capillary rheometry indicated that the viscosity of the materials is the same as that of neat PLA. These results were confirmed by the higher fluidity index in the MFI analysis. Originality/value This paper presents an alternative for the applications of nanocomposites in additive manufacturing processes in FDM systems.

Mechanical and rheological properties of wood plastic composites based on polypropylene and birch plywood sanding dust

Article summarizes investigation results of thermal, mechanical and rheological properties of industrially prepared two new wood plastic composites, based on a virgin polypropylene (PP) and birch plywood production residues-plywood sanding dust (PSD). The studies revealed that the tensile strength of composites increased about 25-30% and the modulus for 4.0-4.5 times, but the lightness, the whiteness degree and the common colour changes are smaller in comparison with previously investigated similar composites [5,6].The softening temperatures by VIKA of approbated composites are 154.4 and 158.6°C. The starting temperatures of thermal oxidation are 250.5 and 253.5°C and the thermal expansion of samples at 90°C is only 3%. The rheological experiments showed the decrease of composite melts viscosity with the increase of temperature and the shear rate, but the fluidity index is smaller than 1, that is typical phenomenon for pseudoplastic polymer liquids. The SEM pictures of the fractured surface replicas confirmed that the composites failure has mixed character: partially fracture the polymer matrix and the border surface of polymer matrix and wood fibre.

Effect of gangue composition on iron nugget production from iron ore–coal composite pellet

The rotary hearth furnace iron nugget process has advantages of short reaction time, high-quality reduced product and wide adaptability of raw materials and meets the trend in ecofriendly development of iron and steel industry. Although the rotary hearth furnace iron nugget process cannot replace blast furnace process, which is affected by production scale, thermal efficiency and technical maturity, it is still a feasible technology for iron production. In order to realize the efficient utilization of high Al2O3 iron ore resources, preparation of iron nuggets with high Al2O3 iron ore was studied. Using iron concentrate as raw material, the effects of slag basicity, Al2O3 and MgO on melting separation of iron ore–coal composite pellets, such as the melting separation temperature, the melting separation time, the morphology of melting separated product, and the recovery rate of iron nugget, were studied. The results showed that relatively low or high liquidus temperature of slag had a negative effect on reduction and melting separation of iron ore–coal composite pellets. The increase in fluidity index of slag resulted in a decline in the melting separation temperature and time of iron ore–coal composite pellets. Optimum basicity to produce iron nuggets using iron ore–coal composite pellets was 0.8–1.0, 0.4 and 0.8 for iron concentrate containing 2, 4 and 6–10 wt.% Al2O3, respectively. Corresponding liquidus temperature and fluidity index of slag were 1300–1475 °C and above 4.5, respectively. Under this condition, the lowest melting separation temperature and the shortest melting separation time of iron ore–coal composite pellets were 1375 °C and 7 min, respectively. The recovery rate of metallic iron in the form of iron nugget could reach about 94%.

Rheological characteristics of aerial lime-based pastes with addition of biopolymers

Viscosity enhancing admixtures are widely used to improve the properties of concrete and ready-mix mortars. This study focuses on the influence of biopolymer (sodium salt of alginic acid, carrageenan, diutan gum, gellan gum, and xanthan gum) in doses of 1, 5, and 10 ‰ on the rheological properties of aerial lime-based pastes. The measurements were carried out on the Discover HR-1 hybrid rheometer with DIN concentric cylinders geometry. On the pastes the flow properties as yield stress, fluidity index and consistency coefficient as well as the viscoelastic properties (complex modulus, loss tangent, critical and flow strain) were studied. All pastes studied expressed shear-thinning behaviour and the flow curves indicated rheopectic character of samples. The significant differences in effectivity of admixtures used were observed. Xanthan and gellan gums were found less effective than the three others in influencing the rheology of aerial lime-based paste while diutan gum was so effective, that the future research with lower doses of the admixture are recommended to better explain its impact on the rheological properties.

Influence of Cellulose Ethers on Fresh State Properties of Lime Mortars

Cellulose ethers (CEs) are widely used as viscosity enhancing, water retaining additives in cement based mortars. Nevertheless, studies about the effect of cellulose ethers on the properties of aerial lime-based mortars are very lack. The use of water retaining additives in lime mortars can influence not only their fresh state properties but also the pore structure and strength of hardened mortars. In this work, four different commercial cellulose ethers were added to lime mortars in order to test their influence on properties of mortars in the fresh state. Mortar rheological parameters (relative yield stress, consistency coefficient and fluidity index) were correlated with flow table tests, relative density measurements, water retention and air content in the mortars. It was found that CEs reduce the spread of lime mortars and increase air content in the mortars. The CEs are not so effective in water retention compared with other types of water retention agents. Most dosages of CEs change the behaviour of mortars from pseudoplastic to dilatant. In contrast to the effect of CEs in cement-based materials, their viscosity enhancing behavior in lime mortars is denied, due to the presence of large amounts of calcium hydroxide. From this point of view, the CEs are not so suitable to use as viscosity enhancing admixtures in lime mortars like derivatives of chitosan or guar gum.

Rheological Properties of Alkali-Activated Brick Powder Based Pastes: Effect of Alkali Activator and Silicate Modulus

The rheological behaviour of alkali-activated materials prepared by activation of a brick powder by alkaline solution (alkali + water glass) is described. The influence of the composition of activation solution (NaOH vs. KOH, varied silicate modulus) on the flow properties (yield stress, consistency coefficient, fluidity index) and the evolution of the elastic modulus (G ́) and the viscous modulus (G ́ ́) over time were studied. The rheological characterization was completed by frequency sweep tests with the aim of investigating the material behaviour more in detail. The results show that the pastes are thixotropic suspensions with very low yield stress. The potassium activator decreases the yield stress and viscosity of the pastes and retards the polymerization kinetic. The brick pastes become more rigid and more viscous with increasing silicate modulus. This also leads to an acceleration of gel formation in brick pastes.

OLEORRESINA DE COPAIBA COMO MATERIA PRIMA PARA LA PRODUCCIÓN DE BIODIÉSEL

On this research, the potential of oleoresin extracted from the tree Copaifera reticulata was analyzed for the production of biofuel starting from the transesterification process. Properties like viscosity, acid, moisture, flash point and melt fluidity index were determined for both the raw and the chemically modified oleoresin. Its behavior on low temperatures and its oxidative stability were included on the characterization. It was determined that the route used for the production of biodiesel is not suitable because it generates a high loss of oleoresin, since the overall performance in biofuel production was approximately 10 %. Still, refining processes and transesterification had a positive effect on the oxidative stability of oleoresin. With respect to raw oleoresin, the stability of refined oleoresin and copaiba biodiesel increased to 46 and 47 oC, respectively. According to the fluidity points, in all cases the behavior on cold fluidity significantly exceeds the established ranges. Copaiba biodiesel showed a fluidity point below –39 oC. According to the values of viscosity and density, the use of oleoresin in its raw or modified forms, although directly conditioned, could be considered in mixtures with gasoil or other biofuels to improve their low temperature properties. Further studies are needed to establish efficient routes for the chemical modification of oleoresin.

EFFECT OF WATER-CEMENT RATIO ON RHEOLOGICAL PROPERTIES OF FOAM CONCRETE MADE OF LOCAL RAW MATERIALS

Abstract. Objectives The purpose of this work is to study the dependency of the fluidity of foam concrete mixtures on the water-cement ratio when using various local aggregates and wastes from the Republic of Dagestan and comparing the fluidity characteristics of mixtures for the same watercement ratios. During the experimental work, the following materials were used: M500 cement, siliceous filler (quartz sand from the deposit in the Kumtorkalinsky district of the Republic of Dagestan with a low modulus of grain size, various synthetic foaming agents), perlite sand, ground expanded clay sand (Kizilyurt, Republic of Dagestan), stone crushing screenings (Kizilyurt, Republic of Dagestan). Methods During the production of foam concrete, a method was used in which foam was prepared in the foam generator, then a solution was prepared from the cement, siliceous component (filler), and water. Then the foam was mixed with the solution in the foam concrete mixer up to the set of the appropriate multiplicity. (The multiplicity in this case was defined as ratio of the volume of the solution of the foam concrete mixture after mixing to the volume of the solution before mixing. During the studies, the water-cement mixture ratio for all three kinds of filler (expanded clay sand, quartz sand from the deposit of the Kumtorkalinsky region, and perlite) was determined. The fluidity index of the foam concrete mixture was determined using a Suttard's viscometer. Results The results of the research indicated that with an increase in the water-cement ratio for all three types of filler (expanded clay sand, quartz sand from the Kumtorkalinsky region and perlite), the foam concrete mixture fluidity index will increase. Conclusion With the same fluidity index values, the mixture with perlite filler has the lowest fluidity, which in turn affects the further structure formation of the foam concrete, allowing the optimal composition with the specified properties to be selected.

The effect of intertidal habitat on seasonal lipid composition changes in blue mussels,Mytilus edulisL., from the White Sea

ABSTRACTThe lipid composition of blue musselsMytilus edulisL. living under different environmental conditions (in the intertidal zone and in aquaculture) was studied to detect origin-related differences in seasonal modifications of lipids, and their fatty acid composition in gills and digestive glands. In early May, the gills and digestive glands of intertidal mussels contained higher amounts of total lipids, chiefly phospholipids and sterols, which appear to perform a protective function as maintenance of membrane integrity. Seasonal modifications in lipid composition of both intertidal and aquaculture mussels were related to environmental factors (mainly low temperature), reproductive processes and food availability. We show that seasonal changes in membrane lipid composition of both intertidal and aquaculture mussels reflect the process of membrane lipid remodelling (namely changes in phosphatidylethanolamine proportion and in the fatty acid composition of phospholipids) required for homeoviscous adaptation in low-temperature conditions. In particular, the unsaturation index and chain fluidity index of phospholipids increased in gills and digestive glands of mussels collected in early May and in November. Similar seasonal changes in the triacylglycerol levels and its fatty acid composition were observed in gills and digestive glands of both intertidal and aquaculture mussels collected in late May and August.

Influence of membrane fatty acid composition and fluidity on airborne survival of Escherichia coli.

Finding ways to predict and control the survival of bacterial aerosols can contribute to the development of ways to alleviate a number of crucial microbiological problems. Significant damage in the membrane integrity of Escherichia coli during aerosolization and airborne suspension has been revealed which has prompted the question of how the membrane fatty acid composition and fluidity influence the survival of airborne bacteria. Two approaches of using isogenic mutants and different growth temperatures were selected to manipulate the membrane fatty acid composition of E. coli before challenging the bacteria with different relative humidity (RH) levels in an aerosol chamber. Among the mutants (fabR - , cfa. fadA - ), fabR - had the lowest membrane fluidity index (FI) and generally showed a higher survival than the parental strain. Surprisingly, its resistance to airborne stress was so strong that its viability was fully maintained even after airborne suspension at 40% RH, a harsh RH level to bacterial survival. Moreover, E. coli cultured at 20°C with a higher FI than that at 30 and 37°C generally had a lower survival after aerosolization and airborne suspension. Unlike FI, individual fatty acid and cyclopropane fatty acid composition did not relate to the bacterial survival. Lipid peroxidation of the membrane was undetected in all the bacteria. Membrane fluidity plays a stronger role in determining the bacteria survival during airborne suspension than during aerosolization. Certain relationships between FI and bacteria survival were identified, which could help predict the transmission of bacteria under different conditions.

Rheological Properties of Wood-Plastic Composites Based on Polypropylene and Birch Wood Plywood Production Residues

Article summarizes investigation results of rheological and thermal stability properties of industrially prepared wood plastic composites, based on virgin polypropylene and birch wood plywood production residues-plywood sanding dust (PSD). WPCs PP+40 wt. % PSD contain different modifiers, such as lubricant Struktol TWP (blend of an aliphatic carboxylic acid salts and mono and diamides), sterically hindered phenolic antioxidant 1010, thermal stabilizer 168 (hydrolytically stable phosphite), UV stabilizer 770-low molecular weight hindered amine light stabilizer (HALS) and pigments based on LDPE. According to our studies, we could conclude that rheological properties studied by capillary rheometer method, strongly depends on WPCs composition. MFI values fluctuate in limits from 0.212 up to 0.724 g/10min. that is changes 3.4 times. Thermal and antioxidant stabilizers promote increase of thermal stability of WPCs noted by TGA. Curves of fluidity indicates character of typical pseudo-plastic liquids for which viscosity not only depends on temperature and shear stress and deformation rate, but also decrease with increase of shear rate. That confirms fluidity index n values which are smaller than 1.

Rheological Properties of Lime Mortars with Guar Gum Derivatives

In this paper, the behaviour of fresh lime mortars modified by etherified derivatives of guar (hydroxypropyl guar (HPG), carboxymethyl hydroxypropyl guar (CMHPG) and native guar gum (GG)) is assessed with the purpose of exploring a new application of such derivatives as lime mortar admixtures. The rheological parameters (relative yield stress, consistency coefficient and fluidity index) and viscoelastic properties were correlated with flow table tests, relative density measurements, water retention abilities of mortars and air content in mortars. Results were seen to be strongly dependent on substituents of the guar. Non-ionic derivative (HPG) exhibited the biggest impact on the yield stress and elastic properties of the mortars. The ionic CMHPG showed the thickening effect. GG had low impact on water retention, while HPG and CMHPG displayed high water retention capability.

Numerical analysis of temperature field in the high speed rotary dry-milling process

For the effect of the temperature field in the ceramic dry granulation. Based on the Euler-Euler mathematical model, at the same time, made ceramic dry granulation experiment equipment more simplify and established physical model, the temperature of the dry granulation process was simulated with the granulation time. The relationship between the granulation temperature and granulation effect in dry granulation process was analyzed, at the same time, the correctness of numerical simulation was verified by measuring the fluidity index of ceramic bodies. Numerical simulation and experimental results showed that when granulation time was 4min, 5min, 6min, maximum temperature inside the granulation chamber was: 70°C, 85°C, 95°C. And the equilibrium of the temperature in the granulation chamber was weakened, the fluidity index of the billet particles was: 56.4. 89.7. 81.6. Results of the research showed that when granulation time was 5min, the granulation effect was best. When the granulation chamber temperature was more than 85°C, the fluidity index and the effective particles quantity of the billet particles were reduced.

Effects of Carboxylic Acids on Osmotic Resistance in Rat and Guinea Pig Red Blood Cells in vitro: The Relationship between Partition Coefficient and Changes in Osmotic Fragility

The osmotic fragility (OF) of isolated Red Blood cells (RBCs) in guinea pigs and rats was examined by monocarboxylic, dicarboxylic and their partition coefficients. A phosphate–NaCl buffer solution that comprises each carboxylic acid at the concentration ranging from 0 to 100 mM was used to incubate dense-packed RBCs at 37°C for 60 minutes. The RBC suspensions were moved into OF test tubes containing NaCl from 0.1 to 0.8%. The hemoglobin concentration was determined and was observed that NaCl concentration induced 50% hemolysis as the OF value. The OF was was increased by dose dependently the exposure to some monocarboxylic acids that possessed hydrocarbon chains of more than 4 carbons in length in case of rats but no increase was observed in guinea pig RBCs. A positive correlation was obtained between the partition coefficients and the degree of change in OF for monocarboxylic acids in the rat, but not in guinea pig RBCs. On the other hand, dicarboxylic acids are corresponding to the monocarboxylic acids had either no effect or decreased OF in rat and guinea pig RBCs. There was no correlation between the partition coefficients and change in OF for monocarboxylic acids in only guinea pig RBCs but for dicarboxylic acids in both rat and guinea pig RBCs. The partition coefficients of the monocarboxylic acids were higher comparatively the corresponding dicarboxylic acids. Whereas monocarboxylic acids are thought to act on the hydrophobic acyl-chain of phospholipids in the deeper regions of the RBC membrane, dicarboxylic acids act on the hydrophilic interface and shallower areas of the RBC membrane. The fluidity index based on fatty acid composition was observed higher in the rat than the guinea pig RBC membrane. The difference in fatty acid composition was speculated to be one of the causes of different OF response to monocarboxylic acids between rat and guinea pig RBCs.

Effect of chitosan ethers on fresh state properties of lime mortars

The fresh state properties of mortars are eminently important since determine the material workability and also have a great influence on its hardened state characteristics. In this paper, the behaviour of fresh lime mortars modified by etherified derivatives of chitosan (hydroxypropylchitosan (HPCH) and carboxymethylchitosan (CMCH)) is assessed with the purpose of exploring a new application of such derivatives as lime mortar admixtures. The rheological parameters (relative yield stress, consistency coefficient and fluidity index) and viscoelastic properties were correlated with flow table tests, relative density measurements, water retention abilities of mortars and air content in mortars. Results were seen to be strongly dependent on substituents of the chitosan. Non-ionic derivative (HPCH) had a plasticizing influence on the mortars; the ionic CMCH showed the thickening effect. The effect of chitosan ethers was found to be dosage-dependent. CMCH had low impact on water retention, while HPCH displayed high water retention capability. It was concluded, that the ionic derivative (CMCH) is very similar by its viscosity enhancing effect to starch ether.