Search Results (31)

Background: Knee osteoarthritis (KOA) is a degenerative joint disorder marked by cartilage degradation, synovial inflammation, and altered synovial fluid (SF) rheology, resulting in pain and impaired joint function. Intra-articular hyaluronic acid (IA-HA) injections aim to restore SF viscoelasticity and improve lubrication; however, their efficacy may be potentiated when combined with physiotherapy (PT). This monocentric observational study evaluated whether the addition of a multimodal PT program to IA-HA therapy enhances SF rheologic properties compared to IA-HA alone. Methods: A total of 52 patients (aged 47–61) with radiographically confirmed moderate KOA (Kellgren–Lawrence grade 2) were enrolled. Patients were assigned to a pilot group (PG; n = 37) receiving IA-HA (Kombihylan^®, 3 MDa) combined with a multimodal PT protocol, or a control group (CG; n = 15) receiving IA-HA alone. The PT program included ten sessions of transcutaneous electrical nerve stimulation, low-level laser therapy, therapeutic ultrasound, progressive exercise, and cryotherapy. SF samples were collected immediately after the first injection and again at six weeks, then analyzed rheologically using the Kinexus Pro+ rheometer. Viscosity parameters were assessed via steady and oscillatory shear tests. Results: At baseline, both groups demonstrated comparable SF viscosity profiles. After six weeks, the PG exhibited significantly higher shear viscosity values across all measured percentiles and reduced variability in rheological parameters, suggesting a more stable intra-articular milieu. Rheometric analysis indicated enhanced SF viscoelasticity, potentially mediated by reduced inflammation and stimulation of endogenous HA synthesis. In contrast, the CG showed inconsistent viscosity changes, reflecting variable responses to IA-HA monotherapy. Conclusions: Combining IA-HA with multimodal PT significantly improves SF rheological properties in moderate KOA patients compared to IA-HA alone. These findings support the role of mechanical stimulation in enhancing joint lubrication and homeostasis, offering a more consistent and effective approach to viscosupplementation. Full article

Currently, the shear-extrusion behavior of solid propellants (SPs), which comprise a significant volume fraction of micro-/nanoscale solid particles (e.g., octogen/HMX), nitroglycerin as a plasticizer/solvent, nitrocellulose as a binder, and other functional additives, is still insufficiently understood. While the rheology of highly filled polymers has been extensively documented, the rheological behavior of SPs within the practical processing temperature range of 80–95 °C remains poorly understood. This study investigated, in particular, the pressure dependence of the viscosity of SPs melts during steady-state shear flow. Steady-state shear measurements were conducted using a twin-bore capillary rheometer with capillary dies of varying diameters and lengths to explore the viscosity dependence of SPs. The results reveal that interface defects between octogen particles and the polymer matrix generate a melt pressure range of 3–30 MPa in the long capillary die, underscoring the non-negligible impact of pressure on the measured viscosity (η). At constant temperature and shear rate, the measured viscosity of SPs exhibits strong pressure dependence, showing notable deviations in pressure sensitivity (β), which was found to be greatly relevant to the contents of solvent and solid particles. Such discrepancies are attributed to the compressibility of particle–particle and particle–polymer networks during capillary flow. The findings emphasize the critical role of pressure effect on the rheological properties of SPs, which is essential for optimizing manufacturing processes and ensuring consistent propellant performance. Full article

The quality and stability of honeys are strongly influenced by their chemical composition and physicochemical properties, which vary with botanical origin. This study examined the physicochemical and compositional properties of cotton, heather, orange, thyme, Christ’s thorn, and chestnut monofloral honey samples, as well as the kinetics of the creaming–crystallization process by monitoring rheological and color parameters. All samples had moisture content lower than the legislation limit (<20%) and a_w ≤ 0.60. Chestnut and heather honeys exhibited the highest electrical conductivity and darkest color. Fructose was the predominant sugar in all samples, with thyme having the highest content. Viscosity decreased exponentially with increasing moisture, with thyme honey being the most viscous. Principal component analysis showed distinct clustering of samples based on their compositional–physicochemical characteristics. Calorimetry revealed the water’s plasticization effect on honey solids, lowering their glass transition temperature, with the data fitting well to the Gordon–Taylor model. Rheometry indicated a Newtonian-like behavior for liquid honeys, evolving towards a pseudoplastic response upon creaming–crystallization. Cotton honey crystallized rapidly, thyme honey showed moderate crystallization propensity, while samples of heather honey gave a diverse response depending on composition. Overall, high glucose content and/or low fructose/glucose ratio promoted honey crystallization, leading to the formation of highly viscous-creamed honey preparations. Full article

Background/Objective: Little information is available on the stability and quality controls of compounded 40% dextrose gel required to ensure its safe use in the treatment and prevention of neonatal hypoglycemia. Whether its efficacy relies on buccal absorption also remains uncertain. This study investigates the stability, microbiological safety, rheological properties and dextrose diffusion of a compounded 40% oral dextrose gel, ensuring it can be widely compounded and stored for clinical use. Methods: A 40% dextrose gel compounded with anhydrous dextrose, carboxymethylcellulose, citric acid, sorbic acid and sterile water was subjected to quality control measures including a dextrose content assay, degradation product analysis, microbiological testing and preservative efficacy. Stability studies were conducted at refrigerated (4–8 °C) and ambient temperatures for 7 days and 3 months, respectively. Rheological properties were assessed, and dextrose permeation was measured through an artificial membrane model that mimics a biological membrane. Results: The compounded gel demonstrated stability for up to 7 days at ambient temperature and 90 days when refrigerated. The dextrose content remained within the acceptable range (90–110%) and microbiological tests confirmed compliance with safety standards. The gel exhibited the consistent rheological properties and shear-thinning behavior appropriate for oral mucosal administration. In vitro permeation studies showed no evidence of dextrose diffusion with a long lag time followed by a low steady-state permeation flux. Conclusions: This study validates the compounding process of a stable 40% oral dextrose gel formulation for neonatal hypoglycemia management, which meets quality control criteria and can be safely administered in clinical practice, offering a cost-effective and safe alternative for neonatal care. Full article

The paper presents the results of research on the rheological properties and stability of oil-in-water emulsions containing cellulose derivatives: methylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose. The continuous phase of the emulsion was a 70% ethanol (EtOH) solution by volume. The dispersed phase consisted of mineral, linseed, and canola oils (20% by volume). Rheological measurements were performed in both steady and oscillatory flow. Emulsion stability was assessed on visual observation and changes in droplet diameter over a period of 5 months after preparation. Relatively stable emulsions were obtained without the addition of low-molecular-weight surfactants, exhibiting viscoelastic properties. The presence of ethanol in the continuous phase significantly slowed down the processes of emulsion sedimentation or creaming, as well as droplet coalescence. The reasons for the slow phase separation were linked to changes in density and zero-shear viscosity of the continuous phase caused by the addition of EtOH. All emulsions were highly polydisperse, and the addition of methylcellulose and hydroxypropylmethylcellulose further led to the formation of strongly flocculated emulsions. Droplet flocculation resulted in highly viscoelastic fluids. In particular, for emulsions containing hydroxypropylmethylcellulose, the ratio of the storage modulus to the loss modulus approached a value close to 0.1, which is characteristic of gels. Full article

Carbonate muds are essential sedimentary components in geological carbon cycles. Model carbonate muds are prepared from crushed, sieved carbonate rock. The carbonate rock particles are primarily smaller than 62.5 µm. Steady-state shear viscosity was measured for model carbonate muds prepared from three types of carbonate rock: limestone Grey, limestone Marl, and limestone Castleton. Model carbonate muds were prepared using fresh water or 3.5 g/L NaCl solution. The carbonate particle concentrations were 1.81 volume percent and 26.95 volume percent, representing semi-dilute and concentrated particle regimes, respectively. Carbonate mud viscosity was measured at temperatures ranging from 8 °C to 35 °C. Shear rates ranged from 60 s⁻¹ to 2500 s⁻¹. Pseudoplasticity occurs at low shear rates and is caused by the release of occluded water during shear-driven breakup and dispersal of particle aggregates. Shear thickening occurs at high shear rates and is caused by transient particle clusters, called hydroclusters, that are reinforced by lubrication forces or frictional particle contacts. Carbonate mud viscosity decreases at increasing temperatures. The presence of 3.5 g/L NaCl in the aqueous phase slightly increased the mud viscosity in the semi-dilute particle concentration regime because of a weak viscosifying effect of NaCl on the aqueous phase. In the concentrated particle regime, electrolytes screened electroviscous effects, reducing the viscosity of muds containing particles with electrically charged surfaces. In aqueous solution, limestone Marl had a comparatively high concentration of charged particles on its surface. Limestone Castleton had a comparatively low concentration of charged particles on its surface. Surface charges were not rheologically evident on limestone Grey. Full article

As a soluble fiber, inulin is present in many plants and has many applications in food and non-food products. In this work, we investigated the rheological properties of inulin dispersions at seven concentrations. The linear viscoelastic properties of inulin were determined using a conventional mechanical rheometer. At 25 wt%, inulin exhibited fluid-like viscoelastic liquid behavior. However, when concentrations were ≥27.5 wt%, inulin exhibited gel-like viscoelastic properties. The viscoelastic properties (moduli and viscosities) increased with increasing inulin concentration. The high-frequency linear rheological properties of inulin were also investigated using the modern light scattering technique, diffusion wave spectroscopy (DWS). The diffusion wave spectroscopy (DWS) measurements showed the amplitude of complex moduli (|G*(ω)|) of inulin gels (≥27.5 wt%) to be proportional to ½ power law of the frequency, which suggests inulin gels behave similarly to flexible polymers. The non-linear steady shear experiments demonstrated that inulin exhibited shear-thinning behavior that was well fitted by a power law constitutive model. The trend of the power law exponent from the experiments indicated that the shear-thinning extent for inulin was greater as the inulin concentration increased. The results of this work indicated that the properties of inulin gel can be manipulated by altering its concentration. Therefore, the desired inulin product can be designed accordingly. These results can be used to direct further food and non-food applications, such as wound healing materials for inulin gels. Full article

Some non-Newtonian fluids have time-dependent rheological properties like a shear stress that depends on the shear history or a stress overshoot that is a function of the resting time, when fluid movement is started. The rheological properties of such complex fluids may not stay constant while they are used in an industrial process, and it is therefore desirable to measure these properties frequently and with a simple and robust device like a pipe rheometer. This paper investigated how the time-dependent rheological properties of a thixotropic and viscoelastic shear-thinning fluid can be extracted from differential pressure measurements obtained at different flowrates along a circular pipe section. The method consists in modeling the flow of a thixotropic version of a Quemada fluid and solving the inverse problem in order to find the model parameters using the measurements made in steady-state conditions. Also, a Maxwell linear viscoelastic model was used to reproduce the stress overshoot observed when starting circulation after a resting period. The pipe rheometer was designed to have the proper features necessary to exhibit the thixotropic and viscoelastic effects that were needed to calibrate the rheological model parameters. The accuracy of rheological measurements depends on understanding the effects that can influence the observations and on a proper design that takes advantage of these side effects instead of attempting to eliminate them. Full article

The high-pressure capillary rheometer (HPCR) represents a state-of-the-art instrument for the determination of rheological properties for plastics and rubber compounds. Rubber compounds have an increased tendency to exhibit flow anomalies depending on the compound ingredients and the processing parameters. Combined with non-isothermal effects due to dissipative material heating, this causes rheological material measurements and the resulting material parameters derived from them to be affected by errors, since the fundamental analytical and numerical calculation approaches assume isothermal flow and wall adhesion. In this paper, the applicability of the empirical rheological transfer function of the Cox–Merz rule, which establishes a relationship between shear viscosity measured with a HPCR and complex viscosity measured with a closed cavity rheometer (CCR), is investigated. The Cox–Merz relation could not be verified for an unfilled EPDM raw polymer or for filled, practical rubber compounds. Using a closed cavity rheometer, a methodology based on ramp tests is then introduced to collect wall slip-free steady-state shear viscosity data under isothermal conditions. The generated data show high agreement with corrected viscosity data generated using the HPCR, while requiring less measurement effort. Full article

The Cox and Merz rules are empirical correlations between the apparent viscosity of polymers with the effect of shear rate and the complex dynamic viscosity with the effect of frequency. In this study, the rheological properties of mayonnaise-type emulsions enriched with Averrhoa carambola extracts were investigated using small-amplitude oscillatory shear (SAOS) and steady shear flow. The results showed that the shear-thinning behavior of the samples was non-Newtonian with yield stress and had time-dependent characteristics, as evidenced by curves from non-oscillatory measurements. It was observed that the experimental data on the complex and apparent viscosity of the samples obeyed the Cox–Merz rule. Full article

Functional, physicochemical, and rheological properties of protein–polysaccharide complexes are remarkably under the influence of the quality of solvent or cosolute in a food system. Here, a comprehensive description of the rheological properties and microstructural peculiarities of cress seed mucilage (CSM)-β-lactoglobulin (Blg) complexes are discussed in the presence of CaCl₂ (2–10 mM), (CSM–Blg–Ca), and NaCl (10–100 mM) (CSM–Blg–Na). Our results on steady-flow and oscillatory measurements indicated that shear thinning properties can be fitted well by the Herschel–Bulkley model and by the formation of highly interconnected gel structures in the complexes, respectively. Analyzing the rheological and structural features simultaneously led to an understanding that formations of extra junctions and the rearrangement of the particles in the CSM–Blg–Ca could enhance elasticity and viscosity, as compared with the effect of CSM–Blg complex without salts. NaCl reduced the viscosity and dynamic rheological properties and intrinsic viscosity through the salt screening effect and dissociation of structure. Moreover, the compatibility and homogeneity of complexes were approved by dynamic rheometry based on the Cole–Cole plot supported by intrinsic viscosity and molecular parameters such as stiffness. The results outlined the importance of rheological properties as criteria for investigations that determine the strength of interaction while facilitating the fabrication of new structures in salt-containing foods that incorporate protein–polysaccharide complexes. Full article

The large-scale implementation of municipal solid waste incineration (MSWI) has put great pressure on waste management and environmental protection. Road construction engineering has also been confronted with the challenges of the heavy consumption of non-renewable mineral resources. Therefore, we evaluated the feasibility of recycling and reusing MSWI residue as an alternative to limestone filler (LF) in transport infrastructure. We investigated the rheological characteristics and fatigue performance of asphalt mastics and mixtures containing MSWI residue. Firstly, a particle size analyzer and environmental scanning electron microscope were adopted to characterize the particle distribution and surface micromorphology of the investigated fillers, respectively. Then, tests for determining the steady shear viscosity and multiple-stress creep recovery were conducted to evaluate the high-temperature rheology of five asphalt mastics. Meanwhile, we used Burgers models with fitting parameters to describe the classic creep recovery measurements and viscoelastic responses. The wheel-tracking test revealed the rutting resistance, and the linear amplitude sweep (LAS) and time sweep tests were combined to investigate the fatigue performances of the five asphalt mastics. A dynamic creep test identified the fatigue life of the asphalt mixtures according to the flow number index. Finally, statistical analysis was conducted to identify the correlations between the rheological and fatigue properties of the mastics and mixtures (R² over 0.87 and 0.78, respectively). Since the fatigue life predictions for the asphalt mastic decreased by over 42.9% according to the MSWI residue/LF volume ratio, the results of the correlations could improve pavement designs. The substitution of the mineral filler in asphalt mixtures with MSWI residue could be a sustainable strategy for the road construction sector. Full article

To explore the influence of pH values on the properties of a compound system containing tea polyphenols (TPs) and low acyl gellan gum (LGG), the color, texture characteristics, rheological properties, water holding capacity (WHC), and microstructure of the compound system were measured. The results showed that the pH value noticeably affects the color and WHC of compound gels. Gels from pH 3 to 5 were yellow, gels from pH 6 to 7 were light brown, and gels from pH 8 to 9 were dark brown. The hardness decreased and the springiness increased with an increase in pH. The steady shear results showed that the viscosity of the compound gel solutions with different pH values decreased with increasing shear rates, indicating that all of the compound gel solutions were pseudoplastic fluids. The dynamic frequency results showed that the G′ and G″ of the compound gel solutions gradually decreased with increasing pH and that G′ was higher than G″. No phase transition occurred in the gel state under heating or cooling conditions at pH 3, indicating that the pH 3 compound gel solution was elastic. The WHC of the pH 3 compound gel was only 79.97% but the WHC of compound gels pH 6 and pH 7 was almost 100%. The network structure of the gels was dense and stable under acidic conditions. The electrostatic repulsion between the carboxyl groups was shielded by H⁺ with increasing acidity. The three-dimensional network structure was easily formed by an increase in the interactions of the hydrogen bonds. Full article

Thermoplastic starch was blended with commercially available biodegradable polyesters of poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) for its improved performance and processability. The morphology and elemental composition of these biodegradable polymer blends were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively, while their thermal properties were analyzed using thermogravimetric analysis and differential thermal calorimetry. For rheological analysis, the steady shear and dynamic oscillation tests of three samples at various temperatures were investigated using a rotational rheometer. All three samples exhibited significant shear thinning at all measured temperatures, and their shear viscosity behavior was plotted using the Carreau model. The frequency sweep tests showed that the thermoplastic starch sample exhibited a solid state at all temperatures tested, whereas both starch/PBAT and starch/PBAT/PLA blend samples exhibited viscoelastic liquid behavior after the melting temperature such that their loss modulus at low frequencies was greater than the storage modulus, and inversion occurred at high frequencies (storage modulus > loss modulus). Full article

Typical extension flow occurs in electrospinning process of Poly(vinylidene fluoride) (PVDF) solutions such that researchers focus on extensional rheological behaviors of PVDF solutions. The extensional viscosity of PVDF solutions is measured to know the fluidic deformation in extension flows. The solutions are prepared by dissolving PVDF powder into N,N-dimethylformamide (DMF) solvent. A homemade extensional viscometric device is used to produce uniaxial extension flows and the feasibility of the viscometric device is verified by applying the glycerol as a test fluid. Experimental results show that PVDF/DMF solutions are extension shinning as well as shear shinning. The Trouton ratio of thinning PVDF/DMF solution is close to three at very low strain rate and then reaches a peak value until it drops to a small value at high strain rate. Furthermore, an exponential model may be used to fit the measured values of uniaxial extensional viscosity at various extension rates, while traditional power-law model is applicable to steady shear viscosity. For 10~14% PVDF/DMF solution, the zero-extension viscosity by fitting reaches 31.88~157.53 Pa·s and the peak Trouton ratio is 4.17~5.16 at applied extension rate of less than 34 s⁻¹. Characteristic relaxation time is λ~100 ms and corresponding critical extension rate is ${\dot{\epsilon }}_c$~5 s⁻¹. The extensional viscosity of very dilute PVDF/DMF solution at very high extension rate is beyond the limit of our homemade extensional viscometric device. This case needs a higher sensitive tensile gauge and a higher-accelerated motion mechanism for test. Full article