Dynamic Rheological Behavior Research Articles

Rheokinetics of microalgae slurry during hydrothermal pretreatment processes

Hydrothermal pretreatment is an efficient process for improving the productivity of biofuels from wet microalgae biomass. The rheological behavior of microalgae slurry is a significant parameter affecting the performance of hydrothermal pretreatment reactors. Herein, the dynamic rheological behavior of microalgae slurry during hydrothermal pretreatment was investigated for the first time. The results revealed that the insoluble organics released from microalgae cells was the main factor affecting the rheological behavior of microalgae slurry. The denaturation and hydrolysis of starch and protein in liquid phase at different temperature regions caused the increasing and decreasing of viscosity of the microalgae slurry, respectively. The rheokinetics equations were established based on four-parameter cross-linking rheokinetics equation to describe the variation of viscosity with reaction time in different temperature. The variation of the rheokinetics model parameters with temperature revealed that the temperature has an obviously positive influence on the hydrothermal pretreatment process of the microalgae slurry.

Isotactic polypropylene toughened with poly(acrylonitrile-butadiene-styrene): compatibilizing role of nano-ZnO

ABSTRACTIn the present work, the toughening effect of poly(acrylonitrile-butadiene-styrene) (ABS) together with nano-ZnO on isotactic polypropylene (iPP) was investigated. Mechanical tests indicated that by introducing ABS and nano-ZnO simultaneously, iPP/ABS/ZnO blends showed not only great enhancement of toughness but also the reinforcement in rigidity. The phase morphology, dynamic rheological behavior and crystalline structure were examined to explain the probable toughening mechanism. The key to toughening of ABS and nano-ZnO on iPP is that the proper content of nano-ZnO selectively disperses at the phase interface between iPP and ABS. With the compatibilization of nano-ZnO, the dispersibility of ABS in iPP and interfacial adhesion between ABS and iPP were obviously improved. Moreover, both nano-ZnO and ABS have β nucleating activity, and ABS surrounded by nano-ZnO can be regarded as a kind of supported β-nucleating agent to significantly induce the formation of β-crystal in iPP matrix. Consequently, good impact toughness and rigidity could be obtained.

Time–Temperature and Time–Water Superposition Principles Applied to Poly(allylamine)/Poly(acrylic acid) Complexes

The dynamic mechanical and rheological behavior of polyelectrolyte coacervates and complex precipitates is of interest for many applications ranging from health to personal care. Hydration is an im...

Dynamic rheological properties of polyurethane-based magnetorheological gels studied using oscillation shear tests.

This paper studies the dynamic rheological behaviors of magnetorheological (MR) gels containing different CIP weight fractions suspended in polyurethane (PU). The dynamic characteristics of prepared MR gels are obtained using large amplitude oscillation shearing (LAOS). The influence of strain amplitude, applied coil current, CIP weight fraction and driving angular frequency on the dynamic rheological properties of MR gels are systematic discussed. The results demonstrate the onset strain from linear viscoelastic region to non-linear viscoelastic region increases with applied coil current. The maximum loss modulus increases with applied coil current and CIP mass fraction. The larger the coil current and CIP mass fraction, the greater the shear strain corresponding to the maximum value. Microstructural variation of self-assembled copolymer chains and magnetic-induced CIP chains at different strain amplitudes, applied coil currents and CIP weight fractions are proposed as an explanation of the non-linear rheological behaviors of PU-based MR gels.

Effect of gellan gum on functional properties of low-fat chicken meat batters.

The effects of substituting pork back-fat with addition of gellan gum and water on gel characteristics, rheological property, water mobility, and distribution of chicken meat batters were studied. The addition of gellan gum significantly affected the cooking yield, color, texture, and rheological property of chicken meat batters (p < .05). The cooking yield and textural properties were not significantly different (p > .05) when gellan gum was added with 0, 0.2, and 0.4%. When the level of gellan gum reached 0.6%, the cooked chicken meat batters had significantly lower L* value, cooking yield, hardness, springiness, cohesiveness, and chewiness values (p < .05). The initial storage modulus (G') of chicken batters was significantly decreased (p < .05) with increasing gellan gum. During the heating, an increase in denaturation temperature of the myosin head and tail were observed in chicken batters with added gellan gum. The G' of chicken batters with 0, 0.2, and 0.4% gellan gum were not significant difference (p > .05) at 80C, but the G' of chicken batters with 0.6% gellan gum was significantly decreased (p < .05). LF-NMR revealed that T21 and T22 were significantly increased (p < .05) with increasing the water and gellan gum content while P21 and P22 were not significantly different (p > .05) in the chicken batters with 0, 0.2, and 0.4% gellan gum. A significant decrease was observed (p < .05) in the chicken batter with 0.6% gellan gum. Overall, added 0.2 and 0.4% gellan gum to chicken meat batters could reduce pork back-fat. PRACTICAL APPLICATIONS: Emulsion-type meat products contain a high level of fat, saturated fatty acids, and cholesterol, which have a potential negative effect on consumers health. However, animal fat plays an important role in the textural properties and water-holding capacity of meat products. One of great challenges in meat processing is how to find a fat substitute to produce low-fat meat products which have overall acceptable quality. This study showed that the addition of gellan gum influenced the textural properties of chicken batters and changed the dynamic rheological behavior. The addition of 0.2 and 0.4% gellan gum kept a stable cooking yield and textural properties of cooked chicken batters and also reduced the pork back-fat. LF-NMR could reflect the cooking yield and gel properties of the chicken batters. Gellan gum may be used to replace pork back-fat to produce low-fat chicken meat batters having overall acceptability in meat industry for meeting consumer demand.

The influence of dynamic rheological properties on carbon fiber-reinforced polyetherimide for large-scale extrusion-based additive manufacturing

Printing high-performance thermoplastics on large scale extrusion-based additive manufacturing platforms requires stability over a range of processing conditions. However, studies on the melt dynamics and processing conditions of these thermoplastics in big area additive manufacturing (BAAM) are limited. This study characterizes the dynamic rheological behavior of polyetherimide (PEI), a high-performance thermoplastic, as well as carbon fiber (CF)-reinforced PEI composites as a BAAM feedstock material. The viscoelastic properties, such as the storage and loss moduli and complex viscosity, are investigated in relation to the BAAM extrusion process. The results show that CF-PEI composites behave like a viscous liquid during BAAM extrusion. The addition of CF to PEI enhances the shear thinning effect and significantly increases the complex viscosity (2.5× increase for 20% CF, and 3× for 30% CF). The increased viscosity increases the torque on the extruder, which may be alleviated by increasing the material processing temperature.

Time‐temperature‐transformation diagram of modified resol phenolic resin and the thermomechanical performance of resol phenolic resin/glass fabric composite

In this paper, modified resol phenolic resin (MPR) and its glass fabric prepreg (MPR/GF prepreg) were fabricated via a hot melt preimpregnated method. To optimize the curing schedule in curing completion, safe processing window, and storage stability conditions, time‐temperature‐transformation diagram dynamic rheological behavior of MPR was established based on such phenomenological changes as viscosity, gelation, and vitrification. The curing behavior of MPR/GF prepreg was further clarified using online monitored dynamic mechanical analysis. At last, thermogravimetric analysis and dynamic mechanical analysis tests were conducted to evaluate the thermomechanical properties of MPR/GF composite. The excellent thermomechanical performance of MPR/GF composite suggests the important role of time‐temperature‐transformation diagram in optimizing the curing cycle and the overall dynamic mechanical properties of the composite.

Metallocenic polyolefin composites with siloxane polymer additives

Blends and composites were obtained by mixing commercial metallocenic linear low density polyethylene (LLDPE) and isotactic polypropylene, with different molecular weight polydimethylsiloxanes (PDMS), including a vinyl ended PDMS. Gamma ray irradiation at different atmospheres was also applied in order to enhance blending by grafting and crosslinking of the radioinduced radicals. Dynamic rheological behavior results suggested that blending increased the viscoelasticity of the blends. Improvement and changes in the abrasive wear behavior was also followed, along with structural properties.

Dynamic shear rheology behavior and long term stability kinetics of reduced graphene oxide filled poly (vinyl alcohol) biofilm

Rheological measurements of bionanocomposites thin films were studied by incorporating chemically reduced graphene oxide in PVA matrix. To examine the effect of reduction of graphene oxide in PVA matrix and its viscoelastic behavior, rheological tests have been conducted. SEM and optical morphology exhibits consistent dispersion of nanoparticles due to the interaction of strong hydrogen bonding in PVA and the presence of other amine functionalities in RGO. TEM micrographs are in agreement with the SEM results and estimated 50–75 nm RGO particle size. The viscosity of solutions result in shear thinning or pseudo plastic behavior and enhancement in elastic behavior is observed on addition of nanofiller. Flow behavior of nanocomposites estimated that lowest value of stress is constrained to induce the flow of material. Incorporation of RGO has immense effect on curing behavior of polymer by arresting the segmental mobility of polymeric chains. Frequency sweep results enquired that 1% RGO has highest long term stability in comparison to pristine PVA. The linear viscoelastic region revealed that the nanocomposites can withstand 0.01 s−1 strain rate without any deformation as a function of frequency. It is investigated that viscosity is decreasing with increasing shear rate at ambient temperature which means the resultant product can be well suited for coating or paint applications.

Influence of the interaction between surfactants and sepiolite on the rheological properties and thermal stability of organo-sepiolite in oil-based drilling fluids

The influence of interaction between organic surfactants and sepiolite (Sep) on the structure and rheological properties of organo-sepiolite (OSep) in oil-based drilling fluids was investigated. Sep was modified with three kinds of cationic surfactant. X-ray diffraction, scanning electron microscope, surface properties, thermal analysis and X-ray photoelectron spectroscopy (XPS) were applied to characterize the structures of OSep and interaction between surfactants and Sep. Gel volume and dynamic rheological behavior were used to appraise the rheological properties of OSep/oil fluids. OSep keeps the crystal structure of sepiolite after organic modification and shows the more dispersed fibers. XPS results demonstrated that organic surfactants are in electronic interaction with sepiolite. Surfactants block the micropores of sepiolite by partially inserting and covering, resulting in the decrease of specific surface area. The size of the surfactants plays an important role to insert the channels. The partially insertion of surfactants into the channels leads to better rheological properties and thermal stability of OSep in oil-based drilling fluids.

Dynamic Rheological Behavior of Low Water-to-binder Ratio Mortars under Large Amplitude Oscillatory Shear (LAOS)

This work focuses on the dynamic rheological behavior of low water-to-binder ratio cement mortars blended with fly ash microspheres (FAM) or silica fume (SF). The initial slump flow of each group has been controlled at similar values by adjusting the superplasticizer dosages. With the help of a coaxial cylinder rheometer, the dynamic rheological behaviors of these mortars are investigated by frequency sweeping in the range of 0–2 Hz under large amplitude oscillatory shear (LAOS). Based on the systematical elaboration of dynamic rheological testing theory, the experimental data are processed according to Lissajous plot fitting to reveal the viscoelastic characteristics. The nonlinearity of response signals is further assessed with Fourier transform (FT) analysis. The parameters, storage modulus G', loss modulus G" and relative amplitude I3/I1 are proposed to clarify the influences of FAM and SF on the stability and energy consumption of local structures and nonlinearity of response torques. The hydration characteristics of various groups well confirmed the rheological phenomenon. This study is beneficial for the preparation and optimization of flow state concrete such as pumping concrete and self-compacting concrete.

Dynamic rheological behavior of poly(ether ketone ketone) from solid state to melt state

ABSTRACTHigh performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η0) and thermal activation energy Ea. Master curves were built and the shift factor aT was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, Ea and η0 were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46456.

Novel nanobiocomposite hydrogels based on sage seed gum-laponite: Physico-chemical and rheological characterization

In this study, the physico-chemical and rheo-mechanical properties of sage seed gum hydrogel, reinforced by various ratios (0–25 wt.%) of Laponite, were investigated. Particles size measurements indicated the formation of large SSG-Laponite microstructures upon nanoparticle adding, due to the interactions generated between the anionic SSG and the charged surfaces of clay platelets. Laponite affected the surface tension and density of the SSG-based systems significantly, but only influenced the ζ-potential above 20 wt.%. The dynamic rheological behavior of SSG-based nanocomposites reflected the reinforcing effect of secondary structures and percolated three-dimensional network, suggested a structural modification of the hydrogels with the Laponite loading. An improvement in texture profile analysis parameters was observed in Laponite content ≤5 wt.%, whereas for nanoparticles >5 wt.%, a significant decrease was obtained. In conclusion, Laponite improved the rheological and physico-chemical properties of SSG-based hydrogel and extended its potential as promising future bio-products for industrial applications.

Steady and dynamic rheological behaviour of frozen soy yogurt mix affected by resistant starch and β-glucan

ABSTRACTThe present study investigated the effect of resistant starch (0, 1%, 2%) and β-glucan (0, 1%, 2%) on the steady and dynamic rheological properties of frozen soy yogurt mixes. The results showed that addition of fibres to the mix caused an enhancement of pseudoplasticity. The power law model was the best model to fit with data. The lowest and the highest of hysteresis loop area belonged to sample containing 1% β-glucan and 2% resistant starch, respectively. Dynamic rheology results showed that storage modulus (G’) and loss modulus (G”) increased within the frequency range of 0.01–100 Hz. The loss tangent (tan δ) of all samples was above 1, indicating liquid viscoelastic behaviour. Resistant starch at concentration of 2% as compared to β-glucan was a better choice to modify the rheological properties of frozen soy yogurt mixes.

Structures and rheological properties of organo-sepiolite in oil-based drilling fluids

Abstract This work reports the characterization of organo-sepiolite (OSep) and the evaluation of the rheological properties of OSep in oil-based drilling fluids. Sepiolite was modified with benzyl dimethyl octadecyl ammonium chloride and OSep samples were prepared. X-ray diffraction, scanning electron microscope, specific surface area and thermal analysis were applied to characterize the structure of OSep. Viscosity, yield point, dynamic rheological behavior and thixotropy were used to appraise the rheological properties of OSep/oil fluids aged at different temperatures. Surfactants coat on the surface of Sep and insert into the channels and tunnels, resulting in lipophilicity and decline of surface area of OSep. Individual fibers, crystal bundles and small particles of OSep form big particles with smooth surface after organic modification. Rheological properties of OSep/oil fluids can be promoted by the increase of surfactants while extremely high surfactant's loading level results in decrease of rheological properties. OSep modified with 35% of surfactant shows the best rheological properties. Temperature rising promotes the rheological properties of OSep/oil fluids by changing the organizations of OSep. However, extremely high temperatures result in deterioration of rheological properties. OSep is a potential rheological additive in oil-based drilling fluids with excellent rheological properties.

Steady and dynamic shear rheological behavior of semi dilute Alyssum homolocarpum seed gum solutions: influence of concentration, temperature and heating-cooling rate.

Alyssum homolocarpum seed gum (AHSG) solution exhibits high viscosity at low shear rates and has anionic features. However there is no information regarding the flow and dynamic properties of this gum in semi-dilute solutions. The present study aimed to investigate the dynamic and steady shear behavior of AHSG in the semi-dilute region. The viscosity profile demonestrated a shear thinning behavior at all temperatures and concentrations. An increase in the AHSG concentration was acompanied by an increase in the pseudoplasticity degree, whereas, by increasing the temperature, the pseudoplasticity of AHSG decreased. At low gum concentration, solutions had more viscosity dependence on temperature. The mechanical spectra obtained from the frequency sweep experiment demonstrated viscoelastic properties for gum solutions. AHSG solutions showed typical weak gel-like behavior, revealing G' greater than G' within the experimental range of frequency (Hz), with slight frequency dependency. The influence of temperature on viscoelastic properties of AHSG solutions was studied during both heating (5-85 °C) and cooling (85-5 °C) processes. The complex viscosity of AHSG was greater compared to the apparent viscosity, indicating the disruption of AHSG network structure under continuous shear rates and deviation from the Cox-Merz rule. During the initial heating, the storage modulus showed a decreasing trend and, with a further increase in temperature, the magnitude of storage modulus increased. The influence of temperature on the storage modulus was considerable when a higher heating rate was applied. AHSG can be applied as a thickening and stabilizing agents in food products that require good stability against temperature. © 2017 Society of Chemical Industry.

Evolution of double crystal melting peak in polypropylene foam assisted by β‐nucleating agent and supercritical CO2

ABSTRACTPolypropylene (PP) foams with double crystal melting peak structure were prepared using supercritical CO2 as blowing agent. Such structure was induced by the β‐nucleating agent (NA) and dissolved CO2 in a lab‐scale autoclave system. From the dynamic rheological behaviors, one can see that long chain branching polypropylene (LCBPP) possess better melt elasticity than linear polypropylene (LPP). In order to improve the foamability, LPP was blended with LCBPP. The results of differential scanning calorimeter and wide‐angle X‐ray diffraction indicated that NA was helpful for the introduction of β‐crystal in LPP, but not for LCBPP and PP blends. Therefore, the foamability and the content of β‐crystal of various PP foams can be effectively controlled by adjusting the ratio of LPP and LCBPP. Meanwhile, both the cooling rate and the content of NA affected the formation of β‐crystal in various PP samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46007.

Effect of Thermoplastic Elastomer on Melt Rheological and Fracture Behavior of Poly(Lactic Acid)

ABSTRACTPoly(lactic acid) (PLA) was melt blended with thermoplastic elastomer, maleic anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) copolymer with varied concentration (10–40 wt%) using twin screw extruder. Dynamic rheological behavior of PLA/SEBS-g-MA blends investigated a transition from liquid-like behavior to solid-like behavior in the composition range of 10–20 wt% of SEBS-g-MA. The capillary rheometer analysis showed enhanced shear viscosity with increase in SEBS-g-MA content. At 10 wt% of SEBS-g-MA, a maximum in the non-essential work of fracture was observed which reflects resistance to crack propagation. Scanning electron microscopy revealed a transition in deformation mechanisms from voids, to fibrillation and cavitation.

Zirconia based feedstocks: Influence of particle surface modification on the rheological properties

Controlling the particle-matrix interface of filled systems is generally an essential challenge for reaching target characteristics. Herein, a simple method is described to characterize and optimize the filler surface chemistry in the case of zirconia feedstocks using stearic acid as a surfactant. Our technique involves contact angle measurements by the sessile drop method between water and thermally treated zirconia powders mixed with stearic acid. It is shown that this is a powerful way to determine the optimum additive concentration and processing parameters. In addition, the effect of coated particles on the dynamic rheological behavior of the molten feedstock is investigated. Furthermore, the kinetics of the hydrophobization of the powder surface induced by esterification between the fatty acid and the adsorbed hydroxyls at the powder surface has been accurately followed.

Rennovia enters piloting stage of bio-based 1,6-HDO process

The application of thermoplastic polyurethanes (TPU) is becoming more and more extensive, and the decreasing of used petrochemical monomers and reduction of energy for the polymerization and processing processes is getting increasingly important. In this paper, we confirmed the positive influence of high bio-based monomers contents (by replacing petrochemical polyol and glycol by bio-based counterparts) on processing and properties of obtained materials. A series of partially bio-based thermoplastic poly(ether-urethane)s (bio-based TPU) were obtained from bio- and petrochemical-based polyols, bio-based 1,4-butanediol, and 4,4′-diphenylmethane diisocyanate by the two-step method without using any solvents. Both the monomers’ origin and polyurethane prepolymer processing parameters were taken into account in characterization of the obtained materials. The TPUs' chemical structure was analyzed by FTIR spectroscopy and 1H NMR and the number average molecular weight was examined by 1H NMR and GPC. The measurements of dynamic mechanical thermal analysis, tensile test, hardness, density method, and rheological behavior provided useful information about the properties of prepolymers and TPUs. The processing properties and an activation energy of prepared materials was examined using the melt-flow index. It has been confirmed that despite the origin of polyols obtained thermoplastic poly(ether-urethanes) exhibited comparably good mechanical and thermo-mechanical properties, and an appropriate melt flow index facilitates their processing. Nevertheless, the use of high amount of bio-based monomers resulted in obtaining more eco-friendly materials.