Strain Sweep Research Articles

Confirmation and understanding the potential emulsifying characterization of persimmon pectin: From structural to diverse rheological aspects

In the study, the structure properties of persimmon pectin (PP) affecting the interfacial performance were characterized firstly. Then, the interfacial behavior of PP at the oil-water interface was evaluated by interfacial tension and interfacial shear/dilatational rheology. Further, the emulsifying and emulsion stabilizing capability of PP were explored based on structure elucidation and interfacial characterization. Structural elucidation of PP indicated that structural characteristics, including high-methylated (71.93 ± 1.23%), lower Mw (4.789 × 104 g/mol), and abundant hydrophobic substances including acetyl-groups (1.21 ± 0.09%), protein (11.54 ± 0.75 mg/g), and ferulic-acid moieties (2.47 ± 0.13 mg/g), contributed to its rapid adsorption to the oil-water interface. Additionally, PP was rich in both homogalacturonan (62.42 ± 1.12%) and rhamnogalacturonan-I (17.75 ± 0.48%) domains, favoring it adsorbed at the oil-water interface. Of all tested emulsifier solutions (1.0%–3.0%, w/v), PP exhibited potent tension-lowering capacity. Additionally, a strong viscoelastic layer of PP (1.0%, w/v) was formed at the oil-water interface based on the interfacial shear (interfacial adsorption and dynamic strain sweep) and interfacial dilatational rheology (interfacial viscoelasticity, frequency and amplitude sweep). Notably, PP exhibited promising emulsifying and emulsion-stabilizing potential, as reflected by small droplet size, creaming thickness (0.68 ± 0.00 mm), and high emulsifying capacity (63.22 ± 1.58%), turbidity (0.37 ± 0.00), etc. By using multi-techniques and multi-scale analysis, the present work effectively correlated the interfacial, structural, droplet characteristics, and bulk emulsion of PP. Results suggested that PP exhibited a promising emulsification potential and could be developed as a novel polysaccharide emulsifier in the food industry.

Fractional derivative viscoelastic response of high-viscosity modified asphalt

To explain the dynamic viscoelastic characteristics of high-viscosity modified asphalt (HVMA) more comprehensively and accurately, one type of finished HVMA and two types of laboratory-produced HVMA were chosen as the research objects. Firstly, a dynamic shear rheometer was employed for the strain sweep test to define the linear viscoelastic range of three different types of HVMA. Then, the frequency sweep test was performed in the linear viscoelastic range under different high-temperature conditions, and the viscoelastic properties of three different types of HVMA were analysed. Finally, an HVMA fractional derivative viscoelastic model was built and compared to the traditional Sigmoid function model. The results demonstrated that the traditional Sigmoid function model has limitations and cannot effectively illustrate the changes in the HVMA over a wide frequency range. The viscoelastic properties of HVMA can be fully described by the 1S1A1D fractional derivative model, including the storage modulus, loss modulus, complex shear modulus, and phase angle variations. For the 1S1A1D fractional derivative model, one Abel dashpot can illustrate the viscoelastic properties of HVMA, and increasing the number of Abel dashpots no significance on the performance.

Characterizing the curing behavior and high-temperature performance of epoxy-resin modified asphalts

This study was undertaken to quantify and analyze the microscopic morphology and curing reaction of epoxy asphalt (EA) modified with 2%, 5%, 10%, 20%, 30%, and 40% epoxy resin (ER) contents. The functional group changes and the ER dispersion before and after the curing reaction, at the micro level, were comparatively evaluated using the infrared spectroscopy and fluorescence microscopy. The influence of various ER contents on the high-temperature performance of EA was also analyzed and quantified, at macro level, using the dynamic shear rheometer (DSR). The research results showed that the particle size of the ER molecules after curing is more significant than before the curing reaction. When the ER content is low, the EA turned into a continuous phase. The peak area of the distinct functional groups in the EA was found to be linearly correlated with the quantitative content of the ER. The strain sweep results showed that the linear viscoelastic region of the EA shrinks after curing. The higher the ER content, the smaller the strain in the linear viscoelastic region. The frequency scanning results showed that the ER significantly increased the composite shear modulus (G*). The rutting factor (G*/Sin δ) showed that when the ER content exceeds 20%, the high-temperature deformation resistance of EA increases and vice versa. The test results of multiple stress creep recovery (MSCR) showed that the deformation recovery ability is significantly improved with increased ER contents after curing. As analyzed using the coefficient of variation (COV), the high-temperature DSR rheological indicated satisfactory statistical reliability with COV values less than 30%.

Field-Dependent Viscoelastic Properties of Graphite-based Magnetorheological Grease

This paper highlights the effect of graphite on the dynamic viscoelastic properties of magnetorheological grease (MRG). Two types of MRG namely MRG and graphite-MRG, GMRG with 0 wt.% and 10 wt. % of graphite respectively was synthesized by using a mechanical stirrer. The rheological properties of both sample at various magnetic field strength from 0 to 0.603 T was analyzed via rheometer under oscillatory mode with strain ranging from 0.001 to 1% with fixed frequency at 1 Hz for strain sweep and frequency ranging from 0.1 to 80 Hz at a constant strain of 0.01 % for frequency sweep. Based on the result obtained, the value of storage and loss modulus are dependent on the graphite content. A high value of storage modulus was achieved in the GMRG sample at all applied magnetic field strengths within all frequency ranges. These phenomena related to the contribution of graphite to forming the chain structure with CIPs and offered a more stable and stronger structure as compared with MRG. Moreover, the reduction in the value of loss modulus in GMRG was noticed compared to MRG at on-state conditions reflected by the stable structure obtained by GMRG. Lastly, both samples displayed a strong solid-like (elastic) behavior due to the high value of storage modulus, G’ acquired compared to loss modulus, G’’ at all frequency ranges. Therefore, the utilization of graphite in MRG can be used in wide applications such as brake and seismic dampers.

Crack growth rate determination of highly dispersible silica filled NR/SBR blends along with material parameters around the crack tip

AbstractBased on the viscous energy dissipation parameter around the crack tip, several intrinsic factors tend to govern the dissipation factor which in turn leads to the characteristic crack growth mechanism of the rubber vulcanizate. Herein, the crack growth behavior of different filled natural rubber (NR), styrene butadiene rubber (SBR), and NR/SBR blends was studied. It was deciphered that the 80/20 NR‐SBR (NSS) compound exhibited the lowest crack growth (dc/dn) value at all strain percentages which was in good accordance with its highest viscous energy dissipation as observed from the DMA (strain sweep) results. Also, from the theoretical calculations, dissipated energy per unit volume for NSS was 4.73 MPa, which was the highest out of all the compounds. This led to a decrement in crack growth. The lowest intensity peak in tan δ versus temperature curve, 6.5% decrement in ΔE'(storage modulus), and almost 44% decrement in ΔG’ (Payne Effect) indicates higher polymer‐filler interaction and lower filler‐filler disintegration respectively, as compared to 100 NR (NRS). The results from optical microscopy and scanning electron microscope suggested that NSS exudes the smallest crack deviation and extent of crack growth with lesser filler agglomerates making NSS the best fatigue‐resistant compound.

Nonlinear viscoelastic behavior and their time-temperature superposition for filled styrene butadiene rubber compounds and vulcanizates

The nonlinear viscoelastic behavior of rubber composites is of great practical importance in their processing as well as the application. In this paper, nonlinear viscoelastic behavior for vulcanized and unvulcanized filled styrene butadiene rubbers (SBR), SBR/carbon black (CB) composites, were mainly investigated. Besides the conventional Payne effect, frequency (ω) sweep tests at different strains (linear and nonlinear viscoelastic regions) were performed to get more information about viscoelastic response, especially in nonlinear region that close to actual driving conditions. Conductivity synchronization test was also operated to explore the evolution of CB agglomerates. It reveals that the filler network structure recovers slowly but the rubber network recovers rapidly during an increasing and decreasing strain sweep cycle. At large strain, rheological parameters of vulcanizates change significantly with increasing ω. A pseudomaster curve based on the ω sweep at large strain and different temperature can be obtained both for compounds and vulcanizates, indicating that the time-temperature superposition is also applicable to the nonlinear viscoelastic behavior. Similar linear and nonlinear viscoelastic behaviors of filled vulcanizates to that of unfilled vulcanizates demonstrate the same mechanism of viscoelastic response. The loss modulus peak of filled vulcanizates primarily comes from the Rouse movement of rubber chains between crosslinking points. Under large strain, the strain amplication effect of particles hardly influence the characteristic relaxation time of Rouse movement between crosslinking points.

Structural build-up and breakdown of sodium hydroxide-activated slag paste assessed using oscillatory rheology

Concentrated suspensions of inorganic binders are thixotropic fluids with non-Newtonian behaviour. In addition to the physical-chemical interactions responsible for the flocculation of the particles, the rheological behaviour in time is affected by the formation of the reaction products. In this paper, this topic was tackled using oscillatory rheology, namely, by increasingly used measurements at the constant strain amplitude and frequency over time (time sweep test), by the combination of these tests with an inserted rotational step (ORO test), and by almost unexplored oscillation amplitude sweep tests, leading to structural breakdown due to increasing strain amplitude. Common sodium hydroxide-activated slag paste was used for this purpose. The results showed that the recovery of the structure is not significantly altered if the sample is remixed at least after 30 minutes of reaction. In addition, the strain sweep tests suggested that the formation of the first reaction products started after about 15 minutes of reaction and had a decisive impact on the evolution of viscoelastic moduli and the corresponding stresses during this kind of test.

Enhanced performance of nano-sized maghemite added carbonyl iron-based magnetorheological soft elastomer

This study examined the MR effects of ferromagnetic rod-like γ-Fe2O3 nanoparticle additives on carbonyl iron (CI)-based magnetorheological (MR) soft elastomers. CI-based isotropic MR elastomers were fabricated using polydimethylsiloxane (PDMS) as the matrix, and silicone oil was added as a plasticizer to make the specimen softer and to enhance the MR properties. The morphology and particle distribution of the fabricated elastomers were analyzed via scanning electron microscopy. Dynamic mechanical spectroscopy was employed to examine the rheological behaviors of the MR elastomers with and without γ-Fe2O3 additive while magnetic fields (H) of varying strength were applied to the samples. The strain and frequency sweep measurements showed that the storage modulus increased with increasing magnetic field strength. Compared with the sample without γ-Fe2O3, the CI/γ-Fe2O3-based MR elastomer exhibited a higher modulus with the Payne effect and the largest enhancement of 15 % in the MR effect was achieved at H = 343 kA/m. The creep and recovery experiments revealed that the γ-Fe2O3 addition rendered the MR elastomer stiffer at all H while comparable recovery ratios were attained for both specimens.

Viscoelastic behavior of filled silicone elastomers and influence of aging in inert and hermetic environment

This article presents a series of experimental investigations on the viscoelastic behavior of silica-filled and silver-filled silicone rubber on the unaged and aged states. The study of specific aging conditions relative to the electronics industry is proposed in this work, namely aging in a hermetic, initially inert atmosphere, at high temperatures. Viscoelastic properties of the materials are measured through DMA tests. Strain sweep tests are carried for the characterization of unaged materials, and frequency sweeps at ambient temperature are performed to characterize the aging-dependent behavior. As a result of the experimental studies, an aging-dependent generalized Maxwell model is proposed in an attempt to describe the evolution in the behavior of silicones due to aging.

Rheological and tribological evaluation of friction modifiers for wheel‐rail applications

AbstractFriction modifiers (FM's) are substances deliberately applied to the top‐of‐the‐rail in the field in order to control the traction coefficient. In this work, two FM's, a commercial (FM1) and a custom‐made (FM2), and a gauge lubricant (CGL) were evaluated in the laboratory using rheological and tribological tests. Two rheological tests were done: oscillatory (frequency and strain sweeps) and flow tests (viscosity vs. shear rate). Tribological tests were done in a twin disk machine to obtain the traction coefficient under different slip values. Retentivity tests were also done in the same machine. Several physical–chemical tests were also done to characterise the products. The results of rheological tests showed that there are notable differences that can influence the performance of FMs. From the studied materials, the FM2 product tends to be more viscous even for high‐shear rates. The tribological tests showed that the traction coefficient is different for all the studied materials and changes from 0.15 to 0.45 depending on the creepage. The retentivity of FM2 is 1.9 times higher than FM1. The results show a good correlation between the rheological behaviour and the coefficient of traction and retentivity.

Ultrasound-induced changes in rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide

Ultrasound is increasingly applied to modify the structures and physicochemical properties of polysaccharides. Hence, this work investigated the ultrasound-induced changes in the rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide (LRP). With an increase in ultrasonic time, the apparent viscosity, storage modulus, loss modulus, and the final percentage recovery of LRP/water system increased to reach the maximum after 10 min treatment and then decreased. These results indicated that short-term (10 min) ultrasound could increase the strength of the network structure of LRP/water system, while longer-term ultrasound (30 and 60 min) weakened the network structure. The self-healing properties of LRP/water system was not affected by ultrasound treatment according to repeated strain and time sweep data. The critical aggregation concentration of the LRP/water system decreased from 2.5 to 1.8 mg/mL after 10 min ultrasound and the number of hydrophobic microdomains increased, suggesting that ultrasound promoted the hydrophobic aggregation of LRP.

Oscillatory behavior with fiber orientation in the flow–vorticity plane for fiber suspension under large amplitude oscillatory shear flow

In fiber suspensions, fibers with three-dimensional orientation states are dramatically flow-oriented in the flow–flow gradient plane when the flow starts. In contrast, large strains are required for flow orientation in the flow–vorticity plane. Under oscillatory shear flow, when the strain amplitude is small, the flow orientation in the flow–vorticity plane is weakly induced, unlike that in the flow–flow gradient plane. The orientation in the flow–vorticity plane increases with the strain amplitude. At large strain amplitudes, fibers are oriented in the flow–flow gradient plane; thus, the rotational motion of fibers in the flow–flow gradient plane is dominant, i.e., fibers are almost flow-oriented in the flow–vorticity plane. However, contributions of the oscillatory behavior of fiber orientation in the flow–flow gradient and flow–vorticity planes to complex viscosity are unclear. In this study, the objective is to determine the contributions of fiber orientation in each plane to complex viscosity with the two initial orientation states (random and flow-oriented states) for the strain sweep test. The two initial orientation states were controlled by manipulating the upper disk of the parallel disk flow path. The initial random state was induced by sliding the upper disk up and down. The initial flow-oriented state was induced by rotating the upper plate. Furthermore, phase transition behaviors from the random to flow-oriented state in the flow–vorticity plane with increasing strain amplitude were qualitatively estimated as the orientation angle via visualization. Consequently, when the initial orientation was random, the fibers gradually vibrated in a medium strain amplitude region, and complex viscosity was higher than that of the initial flow-oriented state. In the conclusion, we divided the complex viscosity behavior of the strain sweep test into five strain amplitude regions and clarified the dominant orientation state in each region. It is conceivable that this result will help in understanding the relationship between fiber orientation and dynamic viscoelastic properties of fiber suspension like fiber-reinforced thermoplastics.

Effect of corneal collagen crosslinking on viscoelastic shear properties of the cornea

The cornea is responsible for most of the refractive power in the eye and acts as a protective layer for internal contents of the eye. The cornea requires mechanical strength for maintaining its precise shape and for withstanding external and internal forces. Corneal collagen crosslinking (CXL) is a treatment option to improve corneal mechanical properties. The primary objective of this study was to characterize CXL effects on viscoelastic shear properties of the porcine cornea as a function of compressive strain. For this purpose, corneal buttons were prepared and divided into three groups: control group (n = 5), pseudo-crosslinked group (n = 5), and crosslinked group (n = 5). A rheometer was used to perform dynamics torsional shear experiments on corneal disks at different levels of compressive strain (0%–40%). Specifically, strain sweep experiments and frequency sweep tests were done in order to determine the range of linear viscoelasticity and frequency dependent shear properties, respectively. It was found that the shear properties of all samples were dependent on the shear strain magnitude, loading frequency, and compressive strain. With increasing the applied shear strain, all samples showed a nonlinear viscoelastic response. Furthermore, the shear modulus of samples increased with increasing the frequency of the applied shear strain and/or increasing the compressive strain. Finally, the CXL treatment significantly increased the shear storage and loss moduli when the compressive strain was varied from 0% to 30% (p < 0.05); larger shear moduli were observed at compressive 40% strain but the difference was not significant (P = 0.12).

Influence of wall slip, thixotropy and lubrication regime on the instrumental sensory evaluation of topical formulations.

Drawing parallels from rheotribology can be used to develop a robust instrumental protocol for non-subjective characterization, product development and design of topical dosage forms with desired sensory attributes. However, instrumental characterization of cosmetic products can be influenced by the measurement protocol, thixotropy, flow anomalies like shear banding or wall slip and nature of the film formed on the skin surface. In this study, we evaluated the influence of above parameters on the instrumental sensory evaluation of 12 topical formulations of different galenic forms. Oscillatory strain sweep measurements (SAOS and LAOS) were performed to investigate the influence of frequency and wall slip on the material parameters. The textural attributes at different consumer touchpoints were evaluated by accounting time-dependent simulation of viscoelastic flow. Further, the influence of film thickness and sample drying on the tactile properties of the topical formulations were studied on a non-biological skin model using a sliding probe tribometer. The study shows that the flow properties of the semi-solid formulations depend on the timescale of the problem. A few formulations exhibited wall slip to varying degrees in the linear viscoelastic regime where the behaviour was found not to be characteristic of a particular topical dosage form. The material functions obtained from the Lissajous plots suggest that the non-linear flow behaviour of different galenic forms is least influenced by the boundary conditions imposed by the measurement geometry. The results were statistically analysed using principal component analysis where the attributes used for discriminating skin creams during pick up and rub out are found to be closely associated with non-linear rheology. The friction coefficient exhibited speed dependence where it formed different parametric group with rheological data depending on the lubrication regime. The study highlights that correlations are possible amongst rheological, tribological and instrumental textural analysis data, which can act an impetus for the development of models to predict attributes that drive perception at different consumer touchpoints. However, the choice of instrumental settings, anomalies associated with rheological measurements and friction dependence on a number of parameters can influence the model prediction.

On the action mechanism of lignosulfonate plasticizer in alkali-activated slag-based system

Workability improvement of alkali-activated materials by common plasticizers used for ordinary Portland cement is usually an issue, but certain effectiveness is often found for lignosulfonate-based plasticizers (LS), especially for activation with sodium hydroxide (its silicate modulus considered as zero). Therefore, the action of LS depending on the silicate modulus of the activator (0, 0.10, 0.25, 0.50) was studied in this paper, using non-traditional oscillation strain sweep tests. The results showed that LS works for silicate moduli of 0 and 0.10 especially in terms of great reduction in the viscoelastic moduli due to a significant decrease in zeta potential magnitude. However, LS had a marginal effect for the silicate moduli of 0.25 and 0.50, which was attributed to the competitive adsorption of LS and silicates from waterglass onto the slag grains. Although splitting of LS chains in NaOH was proven using X-ray photoelectron spectroscopy, electrostatic repulsion of smaller fragments is preserved.

Enhanced performance of cellulose nanofibre reinforced styrene butadiene rubber nanocomposites modified with epoxidised natural rubber

The present work focuses on the potential use of Pandanus kaida proproot cellulose nanofibre as reinforcing filler for styrene butadiene rubber (S) vulcanizates in the presence of epoxidised natural rubber (E) as modifier. The incompatibility between the polar cellulose and non-polar styrene butadiene rubber can be overcome by the use of epoxidised natural rubber (E). This is a facile process compared to other strategies where cellulose nanofibers are chemically modified thus making the process expensive. Initially, cellulose nanofibre was extracted from Pandanus kaida prop root via hydrothermal assisted oxalic acid hydrolysis. FESEM image revealed that cellulose nanofibres (PN) had a diameter of around 15–30 nm. S/PN masterbatches were prepared via latex stage mixing, co-coagulated, later melt-mixed with E and other compounding ingredients followed by vulcanisation. The investigation of mechanical properties revealed that PN nanofiber at 5 phr loading (S/PN5) resulted in enhanced properties. For further improvement, epoxidised natural rubber (E) was used as modifier at various loadings in S/PN5. At 1 phr of E loading (S/PN5/E1), the tensile strength, modulus, tear strength and abrasion resistance index improved significantly by 150%, 47%, 93% and 19%, respectively, compared to S gum vulcanizates. Strain sweep studies indicated better fibre-matrix interaction in the presence of E1. DMA studies revealed a higher storage modulus, lower damping, higher cross-link density and lower adhesion factor for S/PN5/E1 composites.

Effect of ultrasonication on rheological aspects and storage stability of O/W emulsions containing Gleditsia caspica galactomannan – Trigonella foenum – graceum galactomannan mixtures

In current study, the effect of ultrasonication on rheological aspects and storage stability of oil-in-water emulsions containing Trigonella foenum – graceum (fenugreek) – Gleditsia caspica mixtures was comprehensively investigated. Power law, Carreau and Figuni – Shoemaker models were considered as best (by evaluating R2 and RMSE values) to fit the shear rate – shear stress, shear rate – apparent viscosity and shear stress – time data. The results of strain and frequency sweep tests demonstrated that control samples (without ultrasound treatment) had viscous like (dilute) behavior. Contrarily, samples treated with ultrasound had gel like (weak gel) behavior. Between utilized galactomannans, Gleditsia caspica galactomannan had more effect on all calculated rheological parameters. Also, existence of both galactomannans in the formulation of emulsions led to better and more enhanced rheological aspects in comparison with samples containing only one galactomannan. This could be attributed to intermolecular bonds and proper interactions (synergistic interactions) between galactomannans which resulted in more stable emulsions.

Effect of static offsets on the nonlinear dynamic mechanical properties of human brain tissue

This study focuses on the variations in the brain tissue dynamic behaviour pointing out new insight into the material nonlinear viscoelasticity. Shear dynamic response curves are obtained in different working conditions in terms of strain sweep and superimposed static compression offsets (SCO) applied in orthogonal direction to the shear. The strain sweep mode is used to study the storage and loss moduli dependence on the amplitude of the applied strain. It is found that the material exhibits linear viscoelastic behaviour up to about 0.1% strain amplitude. Above this critical threshold, the storage modulus G′ decreases rapidly with increasing dynamic strain amplitude and this effect is gradually intensified as the SCO are increased. In addition, it is observed that the loss factor (G’’/G′) increases by increasing the SCO applied to the specimens. The dynamic strain amplitude results of the storage modulus reveal that the elastic component of the brain tissue's stiffness (G′) evaluated at low strain strongly increases with increasing static superimposed compression strain while the loss factor in the same strain range appears to be SCO independent. Finally, dynamic stiffness recovery after a large strain deformation is considered. The reduction in low amplitude dynamic modulus and subsequent recovery kinetics due to a perturbation is found to be independent of the level of the SCO. The same assessments were carried out on 5 consecutive strain sweep cycle loading. It has been noticed that at the last cycle, the dissipation peak is reduced, and the non-linearity of the curve begins earlier. This could be explained by the effects of cerebral edema on cells and their surrounding environment.

On the analysis of uniaxial cyclic strain sweep test results to bituminous binders: stiffness-phase angle curve

On the analysis of uniaxial cyclic strain sweep test results to bituminous binders: stiffness-phase angle curve

Field-Dependent Rheological Properties of Magnetorheological Elastomer with Fountain-Like Particle Chain Alignment.

Magnetorheological elastomer (MRE) consists of magnetic particles known as carbonyl iron (CIPs), which have been locked in a silicone-based matrix, in various alignments. However, current MRE exhibits inadequate rheological properties due to several issues such as particle alignments. Therefore, in this study, a new approach of the particle alignment of CIPs in MRE, namely fountain-like structure, is introduced. It is expected that this kind of MRE exhibits enhancement rheological responses, in off- and on-state conditions. This work includes the development of a new mold that can produce various directions of magnetic flux lines in order to have fountain-like structures of CIPs in MRE, during the curing process. Three types of particle alignments in MRE, namely isotropic, fountain-like and inverted fountain-like, are fabricated. The rheological properties of MRE in terms of storage modulus and MR effect are measured in an oscillatory shear mode using a rheometer. The results have revealed that fountain-like MRE exhibits higher storage modulus than the isotropic MRE, approximately 0.6 MPa of increment in the strain sweep test, in an on-state condition. Furthermore, it has been demonstrated from strain, frequency and the current sweep test that the rheological properties of fountain-like MRE related to storage modulus and magnetorheological (MR) effect are higher compared to the inverted fountain-like MRE.