Large Amplitude Oscillatory Shear Research Articles

Nonlinear oscillatory rheology of aqueous suspensions of cellulose nanocrystals and nanofibrils

In this work, the nonlinear rheological behavior of aqueous suspensions composed of two typical nanocellulose [rod-like cellulose nanocrystals (CNCs) and filamentous cellulose nanofibrils (CNFs)] was examined and compared by using various large-amplitude oscillatory shear (LAOS) analysis methods, such as Fourier-transform rheology, stress decomposition, Chebyshev polynomials, and the sequence of physical processes. From our analysis, the nonlinear rheological parameters of higher harmonics, dissipation ratio, strain hardening ratio, shear thickening ratio, transient modulus, and cage modulus were obtained and quantitatively analyzed. CNCs tend to assemble to form anisotropic structures in an aqueous medium while the CNFs are entangled to form gels. The CNF suspensions demonstrated a significant viscous modulus overshoot and had stronger yield stresses, but the yield of CNC suspensions was more ductile. In the case of low concentrations, the CNF suspensions demonstrated stronger intracycle shear thickening behavior in medium-amplitude oscillatory shear region and lower dissipation ratios at small strain amplitudes. Although both nanocellulose suspensions revealed the existence of four intracycle rheological transition processes (viscoplastic deformation, structural recovery, early-stage yielding, and late-stage yielding), the CNF suspensions exhibited a stronger structural recovery ability. Larger strain amplitudes did not invariably result in a broader range of intracycle rheological transitions, which are also affected by the excitation frequency. The application of the various LAOS analysis methods provided valuable intracycle nonlinear rheological insights into nanocellulose suspensions, which are of great importance for enhancing their industrial perspectives.

Nonlinear viscoelasticity of Melaleuca alternifolia essential oil Pickering emulsion stabilized with cellulose nanofibrils

Pickering emulsions are suitable technological approaches to stabilize the bioactive compounds of essential oils (EOs) with economic interests for the pharmaceutical, cosmetic and food industries using atoxic and renewable stabilizers, such as cellulose nanostructures. The Melaleuca alternifolia essential oil (MaEO) is recognized for its pronounced antimicrobial performance, which has attracted your interest in developing eco-friendly antiseptic products. In this contribution, we report the nonlinear viscoelasticity behavior of MaEO-in-water Pickering emulsions stabilized by cellulose nanofibrils (CNF) using Large Amplitude Oscillatory Shear (LAOS) tests. The rheological characterizations by Fourier Transform (FT) rheology spectroscopy and Lissajous plots enabled the correlation of the viscous and elastic behaviors with the physical processes involving the deformation of the emulsion. Also, the internal structure of the emulsion was elucidated by fluorescence optical microscopy. Several findings relative to the effects of the shear deformation amplitude over the nonlinear viscoelasticity of the emulsified system are reported here, which are essential to the industrial processes used to develop technological products.

Chitosan catechol-tannic acid composite hydrogel and cryogel with antimicrobial and hemostatic properties

Hydrogels containing catechol group have received attention in the biomedical field due to their robust adhesive/cohesive capabilities, biocompatibility, and hemostatic abilities. Catechol-functionalized chitosan holds promise for preparing self-assembly hydrogels. However, issues of inefficient gelation and instability still persist in these hydrogels. In the current study, we synthesized chitosan catechol (CC) of high catechol substitution (~28 %) and combined CC with tannic acid (TA, which also contains catechol) to form self-healing CC-TA hydrogels. The catechol-enriched CC-TA composite hydrogels showed rapid gelation and mechanical reinforcement (shear modulus ~110 Pa). In situ coherent small-angle X-ray scattering (SAXS) coupled with rheometry revealed a morphological feature of mesoscale clusters (~20 nm) within CC-TA hydrogel. The clusters underwent dynamic destruction under large-amplitude oscillatory shear, corresponding with the strain-dependent and self-healing behavior of the CC-TA hydrogel. The composite hydrogel had osmotic-responsive and notable adhesive properties. Meanwhile, CC-TA composite cryogel prepared simply through freeze-thawing procedures exhibited distinctive macroporous structure (~200 μm), high water swelling ratio (~7000 %), and favorable compressive modulus (~8 kPa). The sponge-like cryogel was fabricated into swabs, demonstrating hemostatic capacity. The CC-TA composites, in both hydrogel and cryogel forms, possessed ROS scavenging ability, antimicrobial activity, and cell compatibility with potentials in biological applications.

Harmonic balance for differential constitutive models under oscillatory shear

Harmonic balance (HB) is a popular Fourier–Galerkin method used in the analysis of nonlinear vibration problems where dynamical systems are subjected to periodic forcing. We adapt HB to find the periodic steady-state response of nonlinear differential constitutive models subjected to large-amplitude oscillatory shear flow. By incorporating the alternating-frequency-time scheme into HB, we develop a computer program called FLASH (acronym for Fast Large Amplitude Simulation using Harmonic balance), which makes it convenient to apply HB to any differential constitutive model. We validate FLASH by considering two representative constitutive models, viz., the exponential Phan-Thien–Tanner model and a nonlinear temporary network model. In terms of accuracy and speed, FLASH typically outperforms the conventional approach of solving initial value problems by numerical integration via time-stepping methods often by several orders of magnitude. Exceptions to this rule are sometimes encountered for materials that are strongly shear thinning or described by constitutive models with discontinuous derivatives. We discuss how FLASH can be conveniently extended for other nonlinear constitutive models, which opens up potential applications in model calibration and selection, and stability analysis.

Influence of axial pressure on the Payne effect of natural rubber vulcanizates

Rubber nanocomposites are key materials for aircraft or automobile tires, which are often subjected to the combined effect of pressure and shear during service. However, the effect of pressure on their strain softening under large amplitude oscillatory shear is not yet clarified. Herein a strain-controlled rotational rheometer is used to investigate the influence of axial pressure on the Payne effect of vulcanized natural rubber composites. Under high axial pressure, the Payne effect of rubber vulcanizates is remarkably suppressed, mainly attributed to the increasing intermolecular local friction hindering wall slip and nonlinear stretching of the rubber network. Furthermore, low temperature, high frequency and high filler fraction may weaken the suppression behavior. The investigation may reveal the role of axial pressure in the strain softening of vulcanized rubber.

Influence of cellulose nanofibers on the behavior of Pickering emulsions. Part II: Thixotropy and dynamic-mechanical tests

Nonlinear rheology of Pickering emulsions is used to further investigate the nonlinear and unrecoverable transformation of inner structures, which is beyond the linear viscoelastic regime of tiny structural disturbances. Exploring various rheological methods plays a vital role in emulsion applications, such as simulating the macroscopic structural transformation between static and liquidlike flow states, strain overshoot, and regeneration for broken structures. According to our previous studies, cellulose nanofibers (CNFs) Pickering emulsions are a typical system for investigating polymer-based emulsions with the auxiliary surfactant [didodecyldimethylammonium bromide (DDAB)] for enhancing CNF absorption. To further study different rheological properties by varying CNF or DDAB contents, multiple interval thixotropic test, large amplitude oscillatory shear, and concentration-time-dependent superposition are employed to study the linear viscoelasticity and structural transformation of nonlinear range. This research was conducted based on the previous published works [Cui et al., Materials 15, 8285 (2022)] as a further characterization for the same sample series.

Impact of Endogenous Lipids on Mechanical Properties of Wheat Gluten Fractions, Gliadin and Glutenin, under Small, Medium, and Large Deformations

The individual viscoelastic responses of gluten proteins and their lipid-removed counterparts were studied under mixing deformations and small, medium, and large deformations selected in the Large Amplitude Oscillatory Shear (LAOS) sweeps. During Farinograph mixing, gliadin reached the 500 BU consistency line after 3.6 ± 0.4 min, while the highest consistency recorded for lipid-removed gliadin was 268 ± 8.4 BU, suggesting a reduction in the water absorption of gliadin in the absence of lipids. The affinity of glutenin to water increased in the absence of lipids, as development time was reached 11 min earlier for lipid-removed glutenin. Under small LAOS strains, tanδ of gliadin remained constant with the removal of lipids, while glutenin’s elasticity decreased (tanδ increased) in the absence of lipids at high frequencies. Intracycle strain-stiffening behavior (e3/e1 > 0) of gliadin increased under medium deformations with high frequency and decreased under low-frequency large deformations as lipids were removed, while this response decreased for glutenin with the removal of lipids only under high-frequency medium and large deformations. Under large LAOS strains, the clockwise rotation of the Lissajous–Bowditch curves for gliadin in the absence of lipids suggested higher intercycle strain-softening and shear-thinning, while the counter-clockwise rotation of the curves for glutenin in the absence of lipids suggested lower intercycle strain-softening and shear-thinning. These results revealed the influence of endogenous lipids on the viscous-dominated response of gliadin and to the elastic-dominated response of glutenin, while balancing the intracycle strain-stiffening behaviors of these gluten proteins especially under large deformations.

Exploring the mechanism of amylose/amylopectin improving formation of yeast-soy protein high-moisture extrudates based on small and large amplitude oscillatory shear rheology

Yeast protein (YP) has high production efficiency and comprehensive nutritional value compared to soy protein isolate (SPI). However, relatively higher proportion of YP replaces SPI seriously affect the structure of extrudates in the production of meat analogues. This study investigated starch addition (amylose/amylopectin) on the structure of YP-SPI extrudates with higher YP proportion and formation mechanism by using closed cavity rheometer simulated the high-moisture extrusion process (mixing, melting, cooling, and extrudates). The proportions of YP:SPI:amylose:amylopectin were set as 5:5:0:0, 5:4:1:0, 5:4:0:1, and 5:4:0.5:0.5. Starch addition could improve the structure formation of extrudes, but the improvement effect varied depending on the type of starch. Compared to amylose, incorporating amylopectin significantly enhanced the fibrous degree of extrudates and improved their tensile resistance. Furthermore, small amplitude oscillatory shear (SAOS) was used to establish texture map. In the mixing and melting zones, amylose decreased the miscibility of protein and starch phase, while amylopectin had positive effect on the integrity and uniformity of protein network. Amylopectin could transform the extrudates into a “mushy” state, contributing to reconstruct protein network. Large amplitude oscillatory shear (LAOS) demonstrated amylopectin had higher energy dissipation ratio in the cooling zone, indicating the uniform “phase separation” facilitated the formation of fiber structure of extrudates. This study provides technical reference for the preparation of high-moisture extrudates using YP as a substitute for SPI based on starch type addition.

Exploring induced microstructural changes in magnetically modified crude oils through nonlinear rheology and magnetometry

Adsorptive phenomena involving dispersed iron oxide superparamagnetic nanoparticles and asphaltenes in crude oil have been profiled as promising technological alternatives, particularly since these interactions can induce significant structural changes within the oil matrices, effectively inhibiting the formation of complex long-range viscoelastic structures. Furthermore, the effect of adsorbed asphaltenes on magnetic dipolar interactions among particles has been proven, showing the formation of multiple asphaltene layers that stimulate a steric repulsive barrier. Despite the discussed hindering phenomena, this research demonstrated the effectiveness of the sequence of physical processes framework to provide intra-cycle structure-rheological interpretations in large amplitude oscillatory shear of a ferrofluid-modified heavy oil, upon the application of an external magnetic field. The analysis proved that disordered nanoparticle/asphaltene aggregates are highly extended and naturally formed in the absence of magnetic forces. In contrast, in the presence of a perpendicular field applied by a controlled rate magneto-rheometer, the formation of interacting structural aggregates of several hundred nanometers was observed, analogous to magnetorheological fluids. These results were validated by adjusting a phenomenological model that effectively represented the intricate processes involved in the formation and reorientation of aggregates, based on the experimental data acquired from zero-field-cooled and field-cooled magnetization curves. This revealed a distinct blocking temperature distribution at around 274 K, which was linked to Brownian relaxation phenomena exhibited by nanoparticle aggregates. In this regard, this research provided a precise extended description of the effect of magnetic fields on the microstructural organization of complex fluids using nonlinear rheology and magnetometry.

Highly distinctive linear and nonlinear rheological behaviors of mucin-based protein solutions as simulated normal and asthmatic human airway mucus

Mucus on the human airway surface normally provides a fluid barrier to trap and remove inhaled hazardous particulates such as viruses and bacteria, a physiological function known as mucus clearance. This function, however, can fail if the mucus has abnormal rheological properties, as in the case of certain lung diseases such as asthma. Despite its importance, airway mucus rheology has not been well studied so far, largely because of its complex nature and limited availability. Therefore, in this study, we prepared mucin-based protein solutions as simulated normal and asthmatic airway mucus (NM and AM, respectively) and subsequently studied them in both linear and nonlinear rheological conditions using either conventional steady-state or large amplitude oscillatory shear experiments together with nonlinear multi-mode Giesekus model analysis. We also examined the microscopic structure of the simulated airway mucus by optical or atomic force microscopy. We found that both NM and AM exhibited typical nonlinear rheological behaviors of protein solutions. However, as compared to NM, AM was much more solid-like, and the viscosity, yield stress, and dynamic modulus were more than ten times that of NM. These differences in macroscopic rheological behaviors between NM and AM could be attributed to their different microstructures. Taken together, this study provides evidence that airway mucus may dramatically change its rheological behaviors with changing chemical composition and microstructure as occurring in diseased conditions such as AM. Thus, the presented rheological assessment and modeling analysis, together with the microscopic characterization of simulated airway mucus, may have important values for better understanding the critical roles of mucus rheology in the determination of the mucus clearance function in health and disease as well as the development of pulmonary drug delivery systems.

Acid-induced gels from mixtures of micellar casein and pea protein: Effect of protein ratio and preheating route

Enhancing the sustainability of dairy products through the partial substitution of dairy proteins with plant proteins requires exploring formulation and processing strategies. This study investigates the gluconic-δ-lactone (GDL)-induced hybrid gels from commercial micellar casein isolate (M) and pea protein isolate (P) dispersions (5% w/w protein content). Variations in the M/P ratios (3:1, 2:2, and 1:3) and preheating routes (Route 1: preheating M and P dispersions together; Route 2: preheating them separately) impacted the physical/conformational properties of protein dispersions as well as the rheological/structural features of resulting gels. Small and large amplitude oscillatory shear (SAOS and LAOS) tests revealed that lower M/P ratio led to earlier gelling points and increased the stiffness and elasticity of hybrid gels in the linear viscoelastic (LVE) region. All gels transitioned from elastic to plastic behavior in the non-linear viscoelastic (NLVE) region, with lower M/P ratio showing reduced stretchability and faster structural breakdown. Regardless of routes, the preheating step (95 °C, 30 min) disintegrated inherent aggregates/agglomerates in these commercial protein ingredients, leading to smaller particle size, but higher protein solubility, surface hydrophobicity, and |ζ-potential|. Pea proteins formed soluble aggregates during preheating, but the presence of micellar caseins (Route 1) hindered this process. Consequently, mixtures with lower M/P ratio and from preheating route 2, possessed higher quantities of pea protein soluble aggregates, forming a compact gel network with low water mobility, as observed by CLSM, STED, and LF-NMR. These findings show the potential for using pea proteins in acid-induced gel foods like yogurt and paneer-type cheeses.

Acid-induced pea protein gels pretreated with media milling: Gelling properties and the formation mechanism

This study explored the effect of stirred media mill (SMM) processing on the acid-induced gelling properties of pea protein. Results showed that SMM treatment enhanced the gel strength from 75.06 g to 183.89 g and increased the water holding capacity from 46.64 % to 73.50 %. The minimum gelation concentration achieved for SMM-treated pea protein was 4 %, significantly lower than that of heat-pretreated pea protein (9 %). SMM decreased protein aggregate size from 104 μm to 180 nm. Microscopy analysis revealed that the small aggregates facilitated the formation of uniform gel networks with tight connections. Linear rheology indicated that small protein aggregates resulted in slower gelation rates with a higher Gʹ for the formed gels. The SMM-pretreated protein gel showed strain hardening, shear thinning behaviors, and satisfactory stability to withstand large-amplitude oscillatory shear. Overall, SMM emerges as a promising technology for producing protein gel products with strong mechanical attributes and customizable rheological properties.

Effects of different salt ions on the structure and rheological behavior of sulfated cellulose nanocrystal hydrogel

Cellulose nanocrystal (CNC) hydrogels are increasingly used in various applications. Here, CNC hydrogels were formed by adding four salt ions (NaCl, KCl, MgCl2, and CaCl2) to sulfated CNC suspensions. NaCl and KCl are monovalent salt ions and MgCl2 and CaCl2 are divalent salt ions; each pair has similar cation charges but different cation radii. This study compared the effects of four salt ions on the structure and rheological behavior of CNC hydrogels. At the same ion concentration, compared with NaCl and KCl, the addition of MgCl2 and CaCl2 significantly reduced the distance between the CNC particles, forming pronounced aggregates and denser network structures. Furthermore, the G′ and G″ of the CNC hydrogels with salt ions followed the order NaCl < KCl < MgCl2 < CaCl2 in the small-amplitude oscillatory shear (SAOS) test, and more viscoelastic hydrogels exhibited relatively lower deformability in the creep-recovery test. Under large-amplitude oscillatory shear (LAOS) conditions, the CNC hydrogels with salt ions exhibited LAOS type III behavior, and the change in yield stress followed the same order as the SAOS results. Among them, CNC hydrogel with CaCl2 exhibited stronger nonlinear response and enhanced strain-stiffening behavior (higher I3/I1 and e3/e1) to resist deformation before 20% strain, as well as an enhanced softening effect (higher |v3/v1|) as the structure was destroyed and rearranged at strains ranging from 20% to 100%. Such CNC hydrogels with different salt ions, which can regulate structural and rheological properties, provide basis for designing hydrogels and meet potential requirements in food and biomedicine fields.

A new method to characterize the nonlinear magneto-viscoelasticity behavior of magneto-active elastomers under large amplitude oscillatory axial (LAOA) loading

The nonlinear viscoelasticity of magneto-active elastomers (MAEs) under large amplitude oscillatory shear (LAOS) loading has been extensively characterized. A reliable and effective methodology, however, is lacking for such characterizations under large amplitude oscillatory axial (LAOA) loading. This is partly due to complexities associated with experimental compression mode characterizations of MAEs and in-part due to their asymmetric stress–strain behavior leading to different elastic moduli during extension and compression. This study proposes a set of new nonlinear measures to characterize nonlinear and asymmetric behavior of MAEs subject to LAOA loading. These include differential large/zero strain moduli and large/zero strain-rate viscosity, which could also facilitate physical interpretations of the inter- and intra-cycle nonlinearities observed in asymmetric and hysteretic stress–strain responses. The compression mode stress–strain behavior of MAEs was experimentally characterized under different magnitudes of axial strain (0.025 to 0.20), strain rate (frequency up to 30 Hz) and magnetic flux density (0 to 750mT). The measured stress–strain responses were decomposed into elastic, viscous and viscoelastic stress components using Chebyshev polynomials and Fourier series. The stress decomposition based on Chebyshev polynomials permitted determination of equivalent nonlinear elastic and viscous stress components, upon which the proposed measures were obtained. An equivalent set of Fourier coefficients was also obtained for estimating equivalent elastic/viscous stress, thereby facilitating faster calculation of the proposed material measures. The proposed methodology is considered to serve as an effective tool for deriving constitutive models for describing nonlinear and asymmetric characteristics of MAEs.

Can numerical methods compete with analytical solutions of linear constitutive models for large amplitude oscillatory shear flow?

Can numerical methods compete with analytical solutions of linear constitutive models for large amplitude oscillatory shear flow?

Rheological study of the effect of clay mineral composition on non-linear viscoelasticity

Due to cyclic loading, clays composed of different mineral compositions exhibit non-linear viscoelastic characteristics. This study quantified the effect of the mineral composition on the non-linear viscoelastic properties of clays. Large-amplitude oscillatory shear rheological tests and cryo-electron microscopy tests were conducted on clays containing quartz, feldspar, montmorillonite, and kaolinite (Q, F, Mt., and Kaol). The results indicated that as the clay content in the soil sample increased, so did the value of relative intensity(I3/1), the Lissajous curves shifted from elliptical to rectangular, and the absolute values of the overall non-linear viscoelasticity parameters (NEand NV) were also larger. In addition, its non-linear viscoelasticity was more prominent, supported by the cryo-electron microscopy test outcomes. Montmorillonite played a more significant role than kaolinite in increasing the nonlinear viscoelasticity of the soil samples. The study findings have significant academic and practical value, facilitating an in-depth understanding of the viscoelastic behavior of clays, rheological studies of other types of clay soils, and geotechnical engineering applications.

A comparison between the FENE-P and sPTT constitutive models in large-amplitude oscillatory shear

The finitely extensible nonlinear elastic with Peterlin closure (FENE-P) and simplified Phan-Thien–Tanner (sPTT) viscoelastic models are used widely for modelling of complex fluids. Although they are derived from distinct micro-structural theories, these models can become mathematically identical in steady and homogeneous flows with a particular choice of the values of the model parameters. However, even with this choice of parameter values, the model responses are known to differ from each other in transient flows. In this work, we investigate the responses of the FENE-P and sPTT constitutive models in large-amplitude oscillatory shear (LAOS). In steady shear, the shear stress scales with the non-dimensional group $Wi/(aL)$ ( $Wi\,\sqrt {\epsilon }$ ) for the FENE-P (sPTT) model, where $Wi$ is the Weissenberg number, $L^2$ is the limit of extensibility in the FENE-P model ( $a$ being $L^2/(L^2-3)$ ), and $\epsilon$ is the extensibility parameter in the sPTT model. Our numerical and analytical results show that in LAOS, the FENE-P model shows this universality only for large values of $L^2$ , whereas the sPTT model shows it for all values of $\epsilon$ . In the strongly nonlinear region, there is a drastic difference between the responses of the two models, with the FENE-P model exhibiting strong shear stress overshoots that manifest as self-intersecting secondary loops in the viscous Lissajous curves. We quantify the nonlinearity exhibited by each constitutive model using the sequence of physical processes framework. Despite the high degree of nonlinearity exhibited by the FENE-P model, we also show using fully nonlinear one-dimensional simulations that it does not shear band in LAOS within the range of conditions studied.

Understanding the rheological properties from linear to nonlinear regimes and spatiotemporal structure of mixed kappa and reduced molecular weight lambda carrageenan gels

Blends of different carrageenan types have proven to be useful in tuning carrageenan gels' rheological properties. However, understanding the influence of a reduced molecular weight on the gelation of mixed carrageenan gels is still limited. Here, the gelation of mixed kappa-(KC) and reduced molecular weight lambda-(LC) carrageenan systems at different mixing ratios was evaluated using rheology from linear to nonlinear regimes via large amplitude oscillatory shear (LAOS), small-angle X-ray scattering (SAXS), pulsed nuclear magnetic resonance (NMR) and particle tracking. A single-step increase in moduli was seen for mixed kappa-lambda carrageenan (KCLC) gels with decreasing temperature while LC demonstrated nongelling behavior. The LAOS response of KCLC mixed gels showed the characteristic signature of strain-stiffening corresponding to the difference in the size and dynamics of the aggregates. The cross-sectional size revealed by SAXS and dynamics of the aggregates revealed by pulsed-NMR demonstrate that KCLC gels has higher segmental mobility and formed small aggregates that reduce with decreasing the KC fraction whereas pure KC gels formed large and rigid aggregates. Thus, the spatiotemporal features of the aggregates are considered to be the origin of the strain-stiffening in mixed gels under large deformation. Moreover, the microscopic properties of the KCLC gels evaluated using particle tracking revealed a homogenous network suggesting the formation of a swollen KC network in the LC solution. Hence, our findings provide insights into the rheological behavior and network structure design of KC and reduced molecular weight LC mixed gels.

Effect of cellulose ether emulsion and oleogel as healthy fat alternatives in cream cheese. Linear and nonlinear rheology, texture and sensory properties

The suitability of oil-in-water (o/w) hydroxypropyl methylcellulose (HPMC)-based emulsions and oleogels to reduce total fat and saturated fat content in cream cheese was studied. The effect of HPMC emulsions and oleogels on spreadability, viscoelasticity, and sensory acceptability of cream cheese was evaluated. Small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS) tests were performed to investigate linear and nonlinear rheology. All cheeses showed a predominance of G’ versus G” with a light dependence of both moduli with frequency in the linear viscoelastic region (LVR). Fat replacement with emulsion or oleogel significantly reduces the values of G’ and G” at the LVR, yield point, and flow point, and increases spreadability. This effect was greatest for the oleogel substitution. However, incorporation of emulsion or oleogel did not significantly affect tan δ, yield stress, yield strain, flow stress, and flow strain. The elastic and viscous evolution during the transition from SAOS to LAOS was similar in all cheeses, despite their differences in spreadability. At large deformation, all samples showed strain-stiffening and shear-thinning behavior. Similar sensory acceptability was found among the oleogel and emulsion cheeses and the control. The similar nonlinear rheological properties among cheeses do not explain the differences in spreadability properties, but explain their similar sensory acceptability. Furthermore, the purchase intention for oleogel and emulsion cheeses increases when consumers receive information on the type and amount of fat.

Non‐linear viscoelasticity of carbon black–fluoroether rubber mixture studied by large amplitude oscillatory shear tests

AbstractNon‐linear viscoelastic characteristics of carbon black (CB)‐filled fluoroether rubber mixture samples are investigated by large amplitude oscillatory shear (LAOS) tests. Three analysis approaches based on LAOS tests are then used to discuss correlations between rheological behavior and CB‐filling amount. Each non‐linear viscoelastic parameter of the mixture presents a three‐stage characteristic with increasing CB content, which are attributed to the alteration of CB–elastomer network structure, corresponding to the state where gum continuous phase, CB–elastomer mesophase, and excessive CB agglomerates predominate in the mixture compound, respectively. According to the findings in engineering experiments, a CB content of 35–40 phr is recommended, taking into account tensile, hardness, and aging properties. Excessive CB agglomerates are found to reinforce CB–elastomer networks at elevated temperatures. For cold‐resistance properties, structural changes in CB–elastomer network are proven to exert little effect on Tg, but a higher CB content was found to slightly enhance the cold‐resistance coefficient, probably due to the decrease in velocity fraction of gum rubber.Highlights LAOS tests were utilized to study the influences of CB on fluoroelastomer; Three‐stage alteration was observed in the mixture with increasing CB content; Correlation between CB content and the engineering properties was discussed.