Controlled Stress Rheometer Research Articles

Does cannula's size alter rheological properties of hyaluronic acid filler?

This study evaluated the rheological properties of various hyaluronic acid (HA) gels after passing through different-sized cannulas (22-G and 25-G). Five commercial brands of highly crosslinked HA fillers were analyzed: (A) Rennova® Ultra Deep, (B) Restylane® Lyft, (C) Hialurox® - Ultra Lift, (D) Belotero® Volume, and (E) E.P.T.Q S500. Rheological characterization was conducted using an automated controlled stress rheometer. The rheological properties of the fillers were assessed both before and after passing through the cannulas. Each filler brand and cannula size was tested three times by a researcher who was blinded to the commercial brands. For data analysis, frequencies of 0.1, 0.5, and 2 Hz were employed. The rheological properties (storage modulus [G'] and loss modulus [G"]) of the high-crosslink HA fillers did not change after being passed through cannulas of different sizes (22-G and 25-G) (p > 0.109) compared to baseline measurements (no cannula). Furthermore, all fillers displayed desirable solid-like, volumizing behavior at low frequencies and strain amplitudes (<10 %). Under physiologically relevant conditions for skin and facial applications, the cannula size did not alter the rheological properties of high crosslink HA fillers.

Three-Dimensional Printing of Red Algae Biopolymers: Effect of Locust Bean Gum on Rheology and Processability.

Seaweeds, rich in high-value polysaccharides with thickening/gelling properties (e.g., agar, carrageenan, and alginate), are extensively used in the food industry for texture customization and enhancement. However, conventional extraction methods for these hydrocolloids often involve potentially hazardous chemicals and long extraction times. In this study, three red seaweed species (Chondrus crispus, Gelidium Corneum, and Gracilaria gracilis) commercialized as food ingredients by local companies were chosen for their native gelling biopolymers, which were extracted using water-based methodologies (i.e., (1) hydration at room temperature; (2) stirring at 90 °C; and (3) centrifugation at 40 °C) for production of sustainable food gels. The potential use of these extracts as bioinks was assessed employing an extrusion-based 3D printer. The present work aimed to study the gelation process, taken place during printing, and assess the effectiveness of the selected green extraction method in producing gels. To improve the definition of the printed gel, two critical printing parameters were investigated: the addition of locust bean gum (LBG) at different concentrations (0, 0.5, 1, 1.5, 2, and 2.5%) and printing temperature (30, 40, 60, and 80 °C). Rheological results from a controlled-stress rheometer indicated that gels derived from G. corneum and G. gracilis exhibited a lower gel strength (lower G' and G″) and excessive material spreading during deposition (lower viscosity) than C. crispus. Thus, G' was around 5 and 70 times higher for C. crispus gels than for G. corneum and G. gracilis, respectively. When increasing LBG concentration (0.5 to 2.5% w/w) and lowering the printing temperature (80 to 30 °C), an enhanced gel matrix definition for G. corneum and G. gracilis gels was found. In contrast, gels from C. crispus demonstrated greater stability and were less influenced by these parameters, showcasing the potential of the seaweed to develop sustainable clean label food gels. Eventually, these results highlight the feasibility of using algal-based extracts obtained through a green procedure as bioinks where LBG was employed as a synergic ingredient.

Exploring Gel-Point Identification in Epoxy Resin Using Rheology and Unsupervised Learning.

Any thermoset resin's processing properties and end-use performance are heavily influenced by the gel time. The complicated viscosity of resin as a function of temperature is investigated in this work, with a particular emphasis on identifying the gel point and comprehending polymerization. Rheology studies carried out using a plate-plate controlled stress rheometer under isothermal conditions were used to compare three experimental techniques for figuring out an epoxy resin's gel point. We also look at the basic modifications that take place during polymerization. We verify the reliability of the three strategies by including Principal Component Analysis (PCA), an unsupervised machine learning methodology. PCA assists in uncovering hidden connections between these methods and various affecting factors. PCA serves a dual role in our study, confirming method validity and identifying patterns. It sheds light on the intricate relationships between experimental techniques and material properties. This concise study expands our understanding of resin behavior and provides insights that are essential for optimizing resin-based processes in a variety of industrial applications.

Viscoelastic behavior of oral mucosa. A rheological study using small-amplitude oscillatory shear tests

The purpose of this work was to determine the viscoelastic behavior of porcine and human oral mucosa under physiological conditions of temperature, hydration and chewing. The linear elastic and viscous shear moduli of these soft tissues were determined by small-amplitude oscillatory shear (SAOS) tests at masticatory frequency using a stress-controlled rheometer equipped with an immersion cell on punched biopsies 8 mm in diameter. Non physiological conditions of temperature were also used to access other parameters such as the denaturation temperature of collagen.First, the different parameters such as normal force, frequency and maximal strain were adjusted to obtain reliable data on porcine mucosa. The optimal normal force was 0.1N and the linear viscoelastic limit was found for a strain amplitude of 0.5% for both 0.1 and 1 Hz. The storage moduli of porcine mucosa, ranging from 5 to 16 kPa, were in the same range as cutaneous tissues determined by SAOS at equivalent frequencies. The storage modulus, superior to the loss modulus G″, indicates a predominant elastic contribution to shear stress in chewing conditions.Second, this protocol evidenced an influence of the anatomic site of the mouth on the viscoelastic behavior of porcine mucosa, mandibular biopsies having higher storage moduli than maxillary biopsies. Temperature scans showed the mechanical manifestation of collagen denaturation in the 60–70 °C range as previous calorimetric analyses. Finally, this mechanical protocol was successfully adapted to characterize human mucosa in an elderly population. It was shown that the elastic modulus is impacted by local inflammation (gingivitis), decreasing significantly from 6 ± 1.4 kPa to 2.5 ± 0.3 kPa.

Characterizing the rheology of lamellar gel networks with optical coherence tomography velocimetry

Lamellar gel networks based on mixtures of cetostearyl alcohol and a cationic surfactant, cetyl-trimethylammonium chloride, were studied using a combination of rheometry and optical coherence tomography (OCT) velocimetry. Experiments were conducted in a stress-controlled rheometer with a parallel plate geometry. Each formulation was found to exhibit a yield stress and thixotropy. The shear start-up behavior in response to a constant stress was directly observed using OCT velocimetry. Close to the yield stress, the velocity had a power law behavior with time after an initial period of transience. At larger stresses, the velocity undergoes two successive increases in power law scaling with time. When sheared at low, constant, shear rates 1–5 s−1, the fluids exhibit plug flow with strong wall slip at both rheometer plates. At rates of 10–150 s−1, the fluids separate into a distinctive three shear band morphology while the wall slip reduces. These rheological properties can be explained by a multilamellar vesicle to planar lamellae transition.

Particles' Organization in Direct Oil-in-Water and Reverse Water-in-Oil Pickering Emulsions.

This paper addresses the impact of the particle initial wetting and the viscosity of the oil phase on the structure and rheological properties of direct (Oil/Water) and reverse (Water/Oil) Pickering emulsions. The emulsion structure was investigated via confocal microscopy and static light scattering. The flow and viscoelastic properties were probed by a stress-controlled rheometer. Partially hydrophobic silica particles have been employed at 1 and 4 wt.% to stabilize dodecane or paraffin-based emulsions at 20 vol.% of the dispersed phase. W/O emulsions were obtained when the particles were dispersed in the oily phase while O/W emulsions were prepared when the silica was introduced in the aqueous phase. We demonstrated that, although the particles adsorbed at the droplets interfaces for all the emulsions, their organization, the emulsion structure and their rheological properties depend in which phase they were previously dispersed in. We discuss these features as a function of the particle concentration and the oil viscosity.

Recycled Carbon Nanofiber-Polypropylene Nanocomposite: A Step towards Sustainable Structural Material Development

Plastic products play a significant role in fulfilling daily necessities, but the non-decomposable nature of plastic leads to inescapable environmental damage. Recycling plastic material is the most appropriate solution to avoid pollution and short product lifespan. The present study shows the recycling effect on carbon nanofiber (CNF) reinforced polypropylene (PP) nanocomposite to attain the purpose of reuse and sustainability. 30 wt% CNF melt-blended with polymer and PP-nanocomposites were fabricated using the injection molding technique. PP-CNF nanocomposites were recycled, and mechanical, thermal, and morphological properties were investigated. Three-point bending and tensile testing showed a low decrement of ~1% and ~5% in bending and tensile strength after recycling 30 wt% PP-CNF nanocomposites. Scanning electron microscopy (SEM) images show that the alignment of CNF was disturbed after recycling due to the decrement in the aspect ratio of CNF. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) showed that the crystallinity of PP increases with recycling. The lowering of interfacial interaction between CNF and PP after recycling was studied by a stress-controlled rheometer. The decrement in mechanical properties of PP-CNF nanocomposite is not significant due to CNF reinforcement; hence, it can be reused for the same or other structural applications.

Steady and dynamic rheological properties of cheese dip: Effect of milk proteins, fat and cheddar cheese

The present study was conducted to investigate the effect of milk protein blends, cheddar cheese and milk fat on rheological properties of cheese dip (CD). The 20 samples of CD were prepared using central composite rotatable design of response surface methodology (RSM) and subjected to rheological study using a controlled stress rheometer. The result obtained showed, all samples manifest shear thinning behavior with an increase in frequency. At shear rate 100 s−1, the apparent viscosity value varied from 1.76 to 6.78 Pas for different samples of CD. Storage (G′) and Loss (G′′) modulus increased, while complex viscosity decreased with an increase in the frequency. The G′, G′′ and Tan δ values for CD varies from 45.73 to 845.33, 40.83 to 457.6 and 0.51 to 0.97, respectively. Furthermore, the values of G′ were higher than the G′′ over the entire range of frequency studied. The rheological parameters studied are most significantly affected by the milk fat followed by protein blend and cheddar cheese. The increase in fat level in CD was positively correlated, whereas increased protein blend and cheddar cheese were negatively correlated with apparent viscosity, G′, and G′′ values. Cheese dip behavior was characterized efficiently by correlating Cross, Carreau-Yasuda and Power-law models with flow curve. The Cross and Carreau-Yasuda models were found to be best fitted (R2 = 0.99) than Power-law model (R2 = 0.90). This study demonstrated, the selection of different level of ingredients during the manufacturing CD for controlling its overall quality. This study also aids in the development of machineries for the commercial manufacturing of cheese dip based on its rheological characteristics.

High-performance integrated manufacturing of a 3Y-TZP ceramic crown through viscoelastic paste-based vat photopolymerization with a conformal contactless support

Ceramic vat photopolymerization has been one of the promising three-dimensional printing technologies for personalized zirconia crown with high dimensional accuracy and surface topography. However, insufficient material stability and complex procedure about auxiliary supports limit the application based on low viscosity slurry. In this work, we developed a photocurable ceramic paste, in which the high static viscosity and high yield stress characteristics allowed it to exhibit sufficient anti-settling and self-supporting capabilities. The rheological characteristics of the as prepared paste were measured by stress-controlled rheometer, and conformal contactless support was designed including top conformal structure without contact with the crown and appropriate empty layer. The 3D precision of crown was evaluated by laser scanning confocal microscope and optical surface scanner. In addition, mechanical properties and biocompatibility of sintered samples were systematically evaluated. The results demonstrated that the yield stress of the ceramic paste approached around 600 Pa, and integrate morphology at the bottom of the crown with the contactless supported zone was observed. 3D deviation between the printed crown scan data and the reference model was reduced within the range of 40–70 µm. Finally, the flexural strength and fracture toughness of the sintered zirconia ceramics reached 1117 MPa and 7.76 MPa⋅m 1/2 , respectively, as well as good biocompatibility by the lack of cytotoxicity and hemolytic reaction. The results indicate an important practical significance for the development of vat photopolymerization printing technology of viscoelastic paste and conformal contactless support strategy to realize the integrated manufacturing of ceramic crowns.

Stress-controlled shear flow alignment of collagen type I hydrogel systems

Disease research and drug screening platforms require in vitro model systems with cellular cues resembling those of natural tissues. Fibrillar alignment, occurring naturally in extracellular matrices, is one of the crucial attributes in tissue development. Obtaining fiber alignment in 3D, in vitro remains an important challenge due to non-linear material characteristics. Here, we report a cell-compatible, shear stress-based method allowing to obtain 3D homogeneously aligned fibrillar collagen hydrogels. Controlling the shear-stress during gelation results in low strain rates, with negligible effects on the viability of embedded SH-SY5Y cells. Our approach offers reproducibility and tunability through a paradigm shift: The shear-stress initiation moment, being the critical optimization parameter in the process, is related to the modulus of the developing gel, whereas state of the art methods often rely on a predefined time to initiate the alignment procedure. After curing, the induced 3D alignment is maintained after the release of stress, with a linear relation between the total acquired strain and the fiber alignment. This method is generally applicable to 3D fibrillar materials and stress/pressure-controlled setups, making it a valuable addition to the fast-growing field of tissue engineering. Statement of significanceControlling fiber alignment in vitro 3D hydrogels is crucial for developing physiologically relevant model systems. However, it remains challenging due to the non-linear material characteristics of fibrillar hydrogels, limiting the scalability and repeatability.Our approach tackles these challenges by utilizing a stress-controlled rheometer allowing us to monitor structural changes in situ and determine the optimal moment for applying a shear-stress inducing alignment. By careful parameter control, we infer the relationship between time, induced strain, alignment and biocompatibility.This tunable and reproducible method is both scalable and generally applicable to any fibrillar hydrogel, therefore, we believe it is useful for research investigating the link between matrix anisotropy and cell behavior in 3D systems, organ-on-chip technologies and drug research.

Experimental investigation of the rheological and phase change behavior of adipic acid as a phase change material (PCM) for thermal energy storage at 150 °C

Phase change materials (PCM) can store and release thermal energy mostly through a transition from solid to liquid and vice versa. This transition and its related parameters such as melting point, enthalpy and heat capacity were most often studied from a thermodynamic point aspect. Investigating the phase transition from a rheological point of view can provide us with important information such as viscosity change during the transition and in the melt. Considering the importance of natural convection during the melting of a PCM, the rheological knowledge can improve the estimations resulting from the numerical analysis of a phase change transition. However, there are a few studies on rheological behavior of PCMs. Here, the rheological behavior of an organic PCM, adipic acid, is studied. This PCM melts at 150 °C which corresponds to a medium temperature range for application in industrial waste heat recovery. Rotational and oscillatory tests under thermal insulation have been performed using a controlled stress rheometer and a plate geometry. Finally, the heat flow measured by Differential Scanning Calorimetry (DSC) is compared to the rheological oscillatory test results to provide a detailed information of phase transition range. To the authors best knowledge, this study is the first study in the rheology of a PCM at medium to high temperature (150 °C).

Rheology investigation of propane gas hydrate crystallization in water/asphaltene-resin-wax deposit emulsions

Hydrates and asphaltene-resin-wax deposits are increasingly concerned as a terrible problem in the field of offshore oil and gas production and transportation. The rheological property of propane gas hydrate in the water-in-asphaltene-resin-wax deposit (W/ARWD) emulsion was in situ characterized by experiments in a stress-controlled rheometer with particular focus on the effects of pressure, emulsion component ratio, and deposit composition. Results demonstrated that the higher pressure could accelerate hydrate formation and aggregation in a shorter time, and exhibit more obvious shear-thinning behavior of hydrate slurry. The emulsion component ratio was positive correlation with the hydrate slurry viscosity and the yield stress, was negative correlation with the hydrate crystallization time. Asphaltene and wax occupied more nucleation sites on water droplets and formed physical barriers to hinder the hydrate crystallization. The promoting effect of resin on hydrate crystallization was stronger than inhibiting effect. With the increase of asphaltene, resin, and wax contents, the yield stress of hydrate slurry gradually increased, and the effect of wax on the yield stress was stronger than asphaltene and resin, which was associated with the multiple effects of capillary bridge between hydrate particles and spatial network of wax crystals. Furthermore, the coupling effect of pressure, emulsion component ratio, and deposit composition on the rheological properties of hydrate slurry had been studied. This study is significant in that it can helpfully support the development of subsea multiphase flow assurance in petroleum production.

Colloidal characteristics of gelatin-treated clay: Intercalation, stability, wettability, and rheological properties

In this paper, sodium montmorillonite was modified with gelatin of different concentrations, and various colloidal characteristics of the gelatin-treated clays were measured and analyzed in detail. First, the influence of gelatin on the interlayer space of Mt layers was investigated by X-ray diffraction analysis. Moreover, the aggregation of Mt particles was examined using a combination of electron microscopy and particle size distribution experiments, while the variation of the electrical property of Mt was measured using ζ potential test. Gelatin of different concentrations can increase the particle size of Mt in different degrees. The addition of 4% gelatin could improve the ζ potential of Mt from −30.65 to −15.55 mV. The wettability change of modified Mt induced by the adsorption of gelatin was followed by measurements of water contact angle and observations of the morphology of Mt/gelatin membrane through SEM images. 4% gelatin could improve the water contact angle of Mt to 81.3°. Finally, the rheological properties of Mt/gelatin dispersion including shear viscosity and shear stress were measured using a stress-controlled rheometer. All of the results were consistent by showing that the overall colloidal characteristics and behavior of the gelatin-treated Mt strongly varied depending on the gelatin concentration used in the modification process. These results can provide a deep and comprehensive understanding of the colloidal properties of clay/gelatin systems and give important guidance for the performance design and improvement of Mt/gelatin composite materials. Furthermore, this study can also be expanded the application of gelatin and its composites to other fields.

Time-Dependent Viscous Flow Behavior of a Hydrophobic Fumed Silica Suspension

The viscous flow behavior of a 12.5 vol% hydrophobic fumed silica (Aerosil® R816) suspension in polypropylene glycol of low molecular weight (PPG400) was studied in a stress-controlled rheometer. The steady flow curve showed shear thickening between two shear thinning regions. Time-dependent viscosity response provoked by step changes in shear stresses corresponding to the shear-thickening region apparently agrees with thixotropic behavior just after the very initial stages are surpassed. Almost instantaneous jamming can justify misinterpretation of the results.

Rheological and flow behavior of water-in-oil Pickering emulsions stabilized with organo-hectorite clay

The rheological and flow behaviors of Pickering emulsions are studied as a function of their water concentration. The studied emulsions are water-in-gasoil inverse emulsions stabilized with organo-hectorite clay. An in-line emulsion preparation was performed and a novel emulsification system was used. The emulsification system was tested and confirmed before performing pipe-flow measurements. A stress-controlled rheometer was used to study the rheological behavior of organoclay stabilized inverse emulsions. It was found that the emulsions exhibited a shear thinning with yield stress non-Newtonian rheological behavior and that the flow curves were well correlated using the Herschel-Bulkley model. Pressure loss and axial velocity measurements were studied to investigate the pipe-flow behavior of the emulsions. Axial velocity of the fluids was measured using an Ultrasonic Pulsed Doppler Velocimeter. It was shown that, up to 50 wt% water mass concentration, an exponential increase of yield stress and viscosity values is noticed, and the phase inversion point is not reached. In the range of the applied flow rates, turbulence took place only in the case of the lowest water cut (0 wt%). The Herschel-Bulkley rheological parameters were used to simulate the pipe-flow behavior of the studied fluids, and showed a satisfactory correlation with the in-line measurements. Furthermore, wall shear stress and velocity profiles were used to study the short-, medium-, and long-term stability of the emulsions.

Influence of monomer type, plasticizer content, and powder/liquid ratio on setting characteristics of acrylic permanent soft denture liners based on poly(ethyl methacrylate/butyl methacrylate) and acetyl tributyl citrate.

We evaluated the influence of monomer type, plasticizer content, and powder/liquid (P/L) ratio on the setting characteristics of light-cured acrylic permanent soft denture liners based on poly(ethyl methacrylate/butyl methacrylate). Two monomers, iso-butyl methacrylate (i-BMA) and 2-ethylhexyl methacrylate (2-EHMA), that contained various concentrations of the plasticizer acetyl tributyl citrate (ATBC) and trace amounts of the photo initiator and reducing agent were used. The P/L ratio was 1.0 or 1.2. The gelation time was measured using a controlled stress rheometer. Materials with i-BMA had shorter gelation times than those for materials with 2-EHMA. The gelation time increased exponentially with increasing plasticizer content. A higher P/L ratio led to a shorter gelation time. The effects of monomer type and plasticizer content were larger than that for the P/L ratio. These results show that 2-EHMA is a suitable monomer for soft denture liners and that the setting characteristics can be controlled via ATBC content.

Apparent wall slip effects on rheometric measurements of waxy gels

The effects of apparent wall slip on rheometric measurements of waxy gels are quantified for gels consisting of a macrocrystalline wax added in mineral oil in concentrations of 3.0 and 7.5 wt. %. The waxy gels are formed in situ in a stress-controlled rheometer, and rheological properties are then obtained. Seven different geometry configurations, including parallel plates, concentric cylinders, and vane, are employed. The surface roughness of the different geometries and wax crystals size are assessed to provide insight into the apparent wall slip phenomenon. In the presence of smooth surfaces, a decrease in approximately 80% in the measured yield stress value is observed in oscillatory tests, regardless of system composition. In addition, the storage modulus measurements are substantially different when obtained from smooth or grooved geometries. In creep experiments, the yield stress measurements decrease by 68%. As expected, apparent wall slip markedly affects the shape of the flow curves obtained, causing the appearance of kinks for smooth Couette geometry. Apparent slip velocities are calculated in the regime just above the yield stress, and it is found that for low concentrations apparent slip increases with concentration and decreases with the ratio between the shear stress and dynamic yield stress. The gathered results also demonstrate that the reproducibility of rheological measurements is improved by using geometries with grooved parts. By quantifying the effects of apparent wall slip on rheological measurements of waxy gels for different geometries, this work can provide useful information for the design of pipelines and oil transportation processes.

Electrorheological behaviors of waxy crude oil gel

The paraffin molecules in crude oil crystalize and precipitate out as the oil cools, resulting in a sharp increase in oil viscosity and further the gelation of the oil. The waxy crude oil gel exhibits complex rheological behaviors, such as viscoelasticity, yield stress, and thixotropy, posing challenges to the flow assurance of pipelines. Previous studies have verified that applying a high-voltage electric field to a flowing liquid oil can significantly reduce its viscosity. In this work, the electrorheological behaviors of waxy crude oil gel are explored by a stress-controlled rheometer equipped with in situ DC electric field manipulation. It is reported for the first time that the gel structure can be significantly weakened upon the application of an electric field for a duration of not less than 10 s, with the yield stress, storage modulus, loss modulus, and apparent viscosity reduced by up to 90%. In addition, the gel structure fracture is observed to transit from brittle-like to ductile-like. A stronger structure weakening effect can be obtained at a higher field strength and lower temperature. The structure weakening effect induced by the electric field can be maintained for a certain period of time after the removal of the electric field, with a recovery of yield stress and moduli less than 10% in 48 h. We hold the view that the electrorheological behaviors of waxy oil should be attributed to the weakened attraction between wax particles induced by the electric field.

Tribo-behaviours of textured point contacts lubricated with low and high consistency lithium greases under reciprocating motion

Tribo-behaviours of grease-lubricated textured point contacts were experimentally explored at heavy loads (characterized in term of Hertzian pressure, P H = 1.5–3.0 GPa) and relatively low sliding speeds (0.2 and 0.4 m s−1) under the linear reciprocating motion employing lithium-based low and high consistency greases. Two contacts (grounded plate versus lapped ball & grounded textured plate versus lapped ball) were employed for the comparative investigations of friction coefficient, specific wear rate, and contact potential. Effects of grease consistency on the greases’ rheological behaviours have also been found at two temperatures 25 °C and 80 °C using controlled stress rheometer. Overall, textured concentrated contacts yielded a low coefficient of friction (reduction up to 24.6%), reduced specific wear rate of the ball (decrease up to 89.5%) and better development of contact potential in comparison to conventional contacts. The transmission electron microscopy (TEM) of used greases collected from textured contacts revealed less degradation in soap fibres. Moreover, the x-ray photoelectron spectroscopy (XPS) revealed the formation of ferric oxide (Fe2O3) and ferrous-ferric oxide (Fe3O4) protective chemical films on the worn surfaces of balls of the conventional and textured contacts.

Kinetic and rheological investigation of cyclopentane hydrate formation in waxy water-in-oil emulsions

Hydrates and waxes are supposed to coexist in the deep-water pipelines under suitable conditions of low temperature and high pressure. Understanding the effect of precipitated wax crystals on hydrate formation and rheological properties of hydrate slurry is crucial to the flow assurance in offshore petroleum production. In this work, a stress-controlled rheometer was used to carry out the rheological experiments for investigating the impact of wax crystals on hydrate formation and yield property of hydrate slurry. The effects of wax content and water cut on cyclopentane (CP) hydrate nucleation and growth were investigated in terms of the measured viscosity data. Log-normal distribution could well fit the probability density histogram of CP hydrate critical time. The logarithmic mean values of CP hydrate critical time decreased with increasing water cut but increased with increasing wax content in water-in-oil (w/o) emulsions. Semi-empirical models were proposed to describe the inhibitory effect of wax crystals on CP hydrate nucleation kinetics by considering the inhibition of mass transfer based on the Freundlich and Langmuir adsorption functions, respectively. Hydrate slurry viscosity rate showed the two-stage characteristics in wax-free w/o emulsions, while four stages could be clearly observed in waxy w/o emulsions. The maximum values of hydrate slurry viscosity rate and calculated hydrate effective volume fraction decreased with increasing wax content. Hydrate growth time was gradually extended as wax content increased. Furthermore, the measured yield stress and yield strain increased with increasing wax content at different water cuts, which was associated with the multiple effect of capillary bridge between hydrate particles, spatial network of wax crystals and coalescence of water droplets. At last, compared to the stress ramp rate, the influence of annealing time on yield stress was more significant.