Dynamic Viscoelastic Parameters Research Articles

Establishment of correlation model between compositions and dynamic viscoelastic properties of asphalt binder based on machine learning

The complex behavior of asphalt binders makes it difficult to accurately predict their dynamic viscoelastic properties. However, the dynamic viscoelastic properties of asphalt binders are determined by their compositions. The main aim of this study was to model the relationship between compositions and dynamic viscoelastic properties in asphalt binders with machine learning algorithms. In this paper, the dataset of dynamic viscoelastic properties parameters was built using DSR test, and the dataset of composition parameters was established using elemental analyzer and infrared spectrometer tests. The effects of asphalt types, oil sources and aging effect on the macro and micro properties of asphalt binder were investigated. The principal component analysis (PCA) and distance correlation coefficient (DCC) methods were adopted to determine the input parameters of the model, while three machine learning algorithms, i.e., SVM, relevance vector machine (RVM) and random forest (RF) were used to predict the dynamic viscoelastic properties of asphalt binders. Results indicate that the content of element C was similar for different samples. The absorption peak at 1700 cm−1 was the most sensitive to oil sources. Nine variables were selected as input factors, namely, A1700, A870, A810, A745, A720, I1600, N, S and C/N. The modeling results show that the SVM performed better in predicting the dynamic viscoelastic properties than RVM and RF. Mean absolute percentage error (MAPE) of all fitting parameters were less than 10 % in SVM. The study enriches the prediction method of asphalt binder dynamic viscoelastic properties and provides technical support for realizing the on-demand design of asphalt material.

Effects of wheat flour supplemented with soy protein concentrate on the rheology, microstructure and water mobility of protein‐fortified precooked noodles

SummaryWheat flour was supplemented with different levels of soy protein concentrate (SPC) and applied to precooked noodles for protein fortification whose quality attributes were characterised in terms of rheology, microstructure and water mobility. The wheat flours with high levels of SPC showed lower enthalpy values and higher temperatures derived from starch gelatinisation. They also exhibited lower values of the pasting viscosity and dynamic viscoelastic parameters. The mixolab measurements demonstrated that the supplement with SPC was effective in raising the water absorption and dough stability of wheat flour. In addition, the use of SPC‐supplemented wheat flours produced precooked noodles with tight and dense structures, which were confirmed by scanning electron microscopic analysis. These microstructural changes were consequently related to higher maximum resistance to extension and lower extensibility of the noodles. However, the SPC‐supplemented wheat flours did not significantly affect the cooking loss of the noodles. Furthermore, three water components with different mobility were observed in the precooked noodles whose spin‐spin relaxation times were distinctly reduced with increasing levels of SPC. Overall similarities in the sensory noodle attributes were detected as wheat flour was supplemented with SPC at a level of 8% (w/w).

DHA and l-carnitine loaded chitosan hydrogels as delivery systems for topical applications

The development of biocompatible hydrogels that allow the controlled release of active components has important applications. In this paper, we report the preparation and characterization of genipin crosslinked chitosan hydrogels loaded with two active components, namely dihydroxyacetone (DHA) or 3-hydroxy-4-trimethylammonium butyrate (l-carnitine), which are used in cosmetics for skin tanning and antiaging effects, respectively. The rheological properties of these hydrogels, as well as their gelling time were investigated. The oscillatory time sweep method was used to monitor the dynamic viscoelastic parameters during in situ gelation experiments, enabling the determination of the gelation time. On the other hand, the effect of the crosslinker concentration, the concentration of active component loaded, and aging time on the rheological properties of hydrogels was also evaluated. It was found that the presence of DHA prolonged hydrogel gelation, if compared to non-loaded or l-carnitine loaded hydrogels at a constant genipin concentration. The slower gelation process observed for DHA loaded hydrogels was due to the existence of DHA-polymer interactions, demonstrated through NMR and DSC characterization. Finally, DHA and l-carnitine release from crosslinked chitosan hydrogels was measured. The results showed that crosslinked hydrogels produced a retarded and more sustained release, in comparison to aqueous solutions and non-crosslinked hydrogels. Such information could give a clear picture on the potential use of chitosan hydrogels, loaded with either DHA or l-carnitine, as delivery systems for topical application of cosmetic ingredients.

Impact of Water on Rheological Behavior of Polyurethane Glues

Abstract Gluing of wood with great moisture content has challenge of water interaction with glue to give unwanted changes in glue properties and formed bond-line. Rheological measurements of polyurethane glues are sufficiently effective method to understand the polymer curing process and viscoelastic properties. Gel formation point is important parameter for a glue from the point of its application. When glue reaches the gel formation point, its viscosity drastically increases so that it could not properly wet the wood and it can result in poor bonds. One-component moisture curing polyurethane glues require water molecules for the polyadditional reaction. When water is involved in the curing reaction, it reacts with the isocyanate groups of glue and can lead to the formation of excessive carbon dioxide and thus can lead to glue penetration out of bond-line, additional backpressure. The dynamic viscoelastic parameters such as complex dynamic viscosity (ή), phase angle (δ), elastic storage modulus (G”), the viscous loss modulus (G”) of two kinds of polyurethane glues depending on added water amount (from 0.9% to 10.0%) at a constant frequency and deformation (oscillation mode) were determined using rheometer. The aim of the present study was to investigate impact of added water on rheological behavior of polyurethane glues. At the end of this study it was concluded that tested glues indicated various behavior depending on chemical composition and added water content. Gel formation point is higher in case of GlueI. However, gel formation time was higher in case of GlueII and was not dependent on added water content. Gel formation time was faster for GlueII. Nevertheless, faster formed gel is stronger than longer formed gel of GlueI.

Rheological characterization and stability study of an emulsion made with a dairy by-product enriched with omega-3 fatty acids

This study involved a rheological characterization of a W/O emulsion manufactured on a pilot scale using omega-3 fatty acids as part of the oil phase and butter milk as the emulsifier. Polyunsaturated omega-3 fatty acids are essential to prevent cardiovascular diseases, improve pulmonary function and also form part of the neurological structure. Buttermilk is a by-product of the dairy industry and has a high organic load which possesses surfactant properties and constitutes a good substitute for conventional emulsifiers in the food industry. The microstructural nature of the emulsion was characterized from the viscoelastic parameters and mechanical spectra. The linear viscoelastic range was determined, from which the maximum stress that the emulsion could withstand from the processing conditions without altering its microstructure was established. In addition, the storage stability of the emulsion was studied to instrumentally predict the rheological behaviour before sensory destabilization of the emulsion was observed. At the frequencies used, a significant decrease in dynamic viscoelastic parameters was periodically observed (G 'and G''), showing a structural change during storage. Furthermore, a coalescence phenomenon was observed after 18 months. The formulation with added omega-3 fatty acids and buttermilk provided a basis for obtaining a functional food as well as adding value to an industrial by-product.

On the influence of microscopic architecture elements to the global viscoelastic properties of soft biological tissue

In this work we introduce a 2D minimal model of random scale-invariant network structures embedded in a matrix to study the influence of microscopic architecture elements on the viscoelastic behavior of soft biological tissue. Viscoelastic properties at a microscale are modeled by a cohort of basic elements with varying complexity integrated into multi-hierarchic lattice obeying self-similar geometry. It is found that this hierarchy of structure elements yields a global nonlinear frequency dependent complex-valued shear modulus. In the dynamic range of external frequency load, the modeled shear modulus proved sensitive to the network concentration and viscoelastic characteristics of basic elements. The proposed model provides a theoretical framework for the interpretation of dynamic viscoelastic parameters in the context of microstructural variations under different conditions.

Dynamic Visco-Elastic Properties of Polycarbonate (PC) under Static and Dynamic Load

The purpose of this work was to investigate the effects of pre-load static load and dynamic load on the visco-elastic in polycarbonate. In the paper, static-dynamic sweep experiment of polycarbonate was performed on EPLEXOR 500N, which was manufactured by GABO of Germany. The variation laws of storage modulus, loss modulus and loss tangent as changing dynamic load in a large range were systematically analyzed and the spectral characteristics of dynamic-viscoelastic under static-dynamic loads were obtained. The experiment results on dynamic visco-elastic under the high load shows that the load effects on dynamic visco-elasticity of polycarbonate performing on the changing of the dynamic visco-elastic parameters, storage modulus become lager with the increasing of static load and decreasing with the increasing of dynamic load, while loss tangent decreases with the increasing of dynamic load and varies in a more complicated pattern as the increasing of static load.

Relationship between the Rheological Properties of Thickener Solutions and Their Velocity through the Pharynx as Measured by the Ultrasonic Pulse Doppler Method

The dependence of the dynamic viscoelastic parameters of carboxymethylcellulose (CMC), xanthan gum, and guar gum solutions on the angular frequency (omega) was compared with that of their viscosity (mu) on the shear rate (gamma). In addition, the effect of these rheological properties on the maximum velocity through the pharynx, V(max), as measured by the ultrasonic pulse Doppler method, was investigated. The CMC and guar gum solutions examined were taken as a dilute solution and a true polymer solution, respectively. The xanthan gum solution was taken as a weak gel above 0.5% and a true polymer solution below 0.2%. The maximum velocity, V(max), of the thickener solutions correlated well with mu, the dynamic viscosity eta', and the complex viscosity eta(*), especially those measured at gamma or omega of 20-30 s(-1) (or rad/s) and above, suggesting that mu, eta', and eta(*) are suitable indexes for care foods of the liquid type for dysphagic patients.

Correlation of Vulcanization and Viscoelastic Properties of Nanocomposites Based on Natural Rubber and Different Nanofillers, with Molecular and Supramolecular Structure

Abstract Elastomer nanocomposites reinforced with low volume fraction of nanofillers, such as nanoclays and carbon nanofibers, have long been known to possess significantly improved mechanical, thermal, dynamic mechanical, flame retardant, and barrier properties. The present work attempts to evaluate the effect of nanofillers (like modified and unmodified montmorillonite, sepiolite, carbon nanofiber, and carbon black) and their amount on vulcanization, as well as dynamic and rheological properties in the prevulcanization and postvulcanization stages. Upon using organomodified nanoclay, optimum cure time was reduced and cure rate index increased; whereas, in comparison, carbon nanofiber resulted in a slower cure. The influence of loading of some representative nanofillers on natural rubber was studied through qualitative description of critical dynamic viscoelastic parameters, which indicated the formation of supramolecular structure even at low volume fraction. The nanocomposite vulcanizates showed solidlike rheological behavior and upon implementation of dispersion techniques the activation energy of flow was reduced by around 60%. The knowledge of cure and rheological properties of the compounds, which evolves from the structure formation, can be utilized for assessing process optimization, cost reduction, and performance of the nanocomposites.

Rheological Study of Genipin Cross-Linked Chitosan Hydrogels

This paper reports the rheological behavior of chitosan solutions that have been cross-linked with different amounts of genipin, at body temperature and physiological pH. The effect of the cross-linker loading on the rheological properties of hydrogels has been evaluated. The oscillatory time sweep method was used to monitor the dynamic viscoelastic parameters during in situ (i.e., in the rheometer) gelation experiments, enabling the determination of the gelation time. The stress and frequency sweeps were employed to measure G' of the cured hydrogels. It was found that the solutions of chitosan cross-linked with genipin, under physiological conditions, could form relatively strong elastic gels when compared to those of pure chitosan. Moreover, the gelation time obtained from the crossover of G'' and G' was in excellent agreement with the value obtained from the Winter-Chambon criterion. A significant reduction on this parameter was achieved even at low genipin concentrations. This behavior suggests that these formulations are able to be produced in situ and thus constitute promising matrices for cells and bioactive molecule encapsulations.

Dynamic Viscoelasticity of Carbon Fibre Reinforced Polymers under High Load: Effects of Static and Dynamic Loads

The load applied on the specimen in common dynamic mechanical thermal analysis (DMTA) is of the order of several Newtons to several tens of Newtons, far lower than that in service life. In this study a dynamic mechanical thermal analyser (EPLEXOR 500, with a total load up to 500 N) was applied to investigate the effects of static load and dynamic load (sine-wave load) on the dynamic viscoelasticity of unidirectional carbon fibre reinforced epoxy resin composites. The effects of the load on the dynamic viscoelasticity of polymer matrix composites (PMCs) are expressed mainly in two ways. On the one hand, the load affects the magnitude of the dynamic viscoelastic parameters. The storage modulus increases with increasing static load and decreases with increasing dynamic load. Such variations are obviously related to the interaction between the two kinds of load. The increase in load, whether static or dynamic, can result in a decline in the loss tangent. On the other hand, there exists a frequency-temperature-load equivalence for a carbon fibre-reinforced polymer's dynamic viscoelasticity. An increase in static load raises the glass-transition temperature and pushes the frequency spectrum curve towards a low frequency, while the effects of dynamic load are the reverse.

Rheological properties of batter systems containing different combinations of flours and hydrocolloids

AbstractThe rheological properties of batters formulated using different combinations of wheat, corn, and rice flours with two types of hydrocolloids, namely methylcellulose (0.5%, 1% and 1.5%) or xanthan gum (0.2%), were studied. Control samples were formulated with combinations of flours without the added hydrocolloids. The effects of hydrocolloids on rheological characteristics of the batter systems were measured using a controlled stress rheometer at a temperature of 15 °C. The effects of hydrocolloids on dynamic viscoelastic parameters as functions of temperatures were evaluated. All the batters showed shear thinning behaviour with flow behaviour indices in the range 0.34–0.67. Addition of xanthan gum lowered the flow index values, imparting a higher degree of pseudoplasticity to the batter samples compared to methylcellulose. The consistency index of the control batter samples varied from 0.46 to 69.2 Pa sn. Addition of xanthan gum or methylcellulose significantly increased the batter consistency index value. The gums changed the onset temperature of structure development, and the storage (G′max) and loss moduli (G″max) of the batter systems. However, no statistically significant effects were observed on the peak temperature of batter systems in which the G′ reached a maximum value. Xanthan gum increased both G′max and G″max, whereas at higher concentrations methylcellulose increased G′max but lowered G″max. Copyright © 2007 Society of Chemical Industry

Changes in rheological properties of grass carp fast skeletal myosin induced by seasonal acclimatization

To elucidate the effects of seasonal temperature acclimatization on thermal gelation of grass carp myosin, myosins from fish in different seasons were prepared and investigated for the changes in dynamic viscoelastic parameters including storage modulus (G′), loss modulus (G″) and damping factor (tan δ) upon heating. Myosins from fish in spring and summer had a temperature region of 38–44°C for the first marked increase of G′ higher than that of myosins from fish in autumn and winter (28–33°C). The measurement temperature-dependent changes in dynamic viscoelastic parameters such as G″ and tan δ were also different among the four myosins. While gel formation was observed with the spring and summer myosins, apparently in two steps, three steps were found in the autumn myosin. Furthermore, the winter myosin exhibited more than three steps for gel formation. These differences in rheological properties among the four myosins were considered to be attributed to the differences in thermodynamic and structural properties of these myosins previously reported.

Dynamic viscoelastic shear properties of soft matter by magnetic resonance elastography using a low-field dedicated system

A magnetic resonance elastography (MRE) based method that consists in measuring dynamic viscoelastic parameters of soft matter by analysis of propagating shear waves at different frequencies is proposed. Dynamic shear tests were performed on soft gels with a dedicated magnetic resonance imaging system at low field (0.1T) and were compared with results obtained with a mechanical rotational rheometer. Storage and loss moduli were plotted against frequency with both methods and good agreement was found between their results in the shared frequency range. Therefore, it is shown that the described method could be a reliable and accessible tool for three-dimensional dynamic mechanical analysis on soft matter able to overcome dynamic range, sample dimensions and directional limitations of mechanical rheometers. Advantages and limits of the method are discussed.

In situ rheometry of cohesive sediments under water wave pressure

The problems and challenges involved in in situ measurement of dynamic mechanical properties of non-rigid mud bed under water wave pressure have been investigated. A detailed preliminary investigation on a natural mud was carried out in a flume-generating monochromatic water waves at a fixed frequency in which dynamic bulk density profile, water turbidity and viscoelastic parameters from the bed response to plane shear waves, were measured with a specially designed measuring device. The device, which is based on the analysis of the characteristics of shear wave field generated within the mud bed, was used in situ at a frequency of 619 Hz. The effect of water wave pressure on the bed was picked up at a fixed location in the form of shear wave pattern for analysis using Fast Fourier Signal Processing technique. The shear wave velocity through the mud and the phase difference between shear stress and shear strain at the wave-generating surface of the device were simultaneously measured. A phase angle of about 18° was obtained for the mud with evidence of bed weakening by up to 57% within the surface wave amplitude that showed no mud surface erosion. The problems inherent in carrying out this type of investigation are also discussed alongside the result obtained that demonstrated the capability of this technique in this type of application.

Rheological Properties of Fast Skeletal Myosin Rod and Light Meromyosin from Walleye Pollack and White Croaker: Contribution of Myosin Fragments to Thermal Gel Formation

Myosin rod and light meromyosin (LMM) of walleye pollack and white croaker were examined for their rheological properties by measuring dynamic viscoelastic parameters. Rods from walleye pollack and white croaker increased their storage moduli (G') in the ranges of 29-43 degrees C and 31-38 degrees C, respectively, in temperature sweep analysis. Walleye pollack LMM showed no peak of G' upon heating, whereas the white croaker counterpart exhibited a single sharp peak of G' at 35 degrees C. Loss modulus (G") showed similar temperature-dependent changes for the two fish species as the case of G', irrespective of rod and LMM, although G" values were lower than those of G'. Thus, rheological properties of rod and LMM were different between walleye pollack and white croaker. Taken together with data previously reported for myosin, it was considered that both myosin rods from walleye pollack and white croaker are attributed to thermal gel formation of myosin in a low-temperature range, though in a species-specific manner.

Relationships between dough and bread viscoelastic properties in enzyme supplemented wheat samples

Dough rheological properties and dynamic mechanical bread parameters have been investigated for relationships to explore the ability of dynamic analysis to characterize fresh bread quality. Rheological assessment of doughs and breads was performed by using empirical and fundamental methods at both small and large deformation. Evaluation of dough properties was carried out by texture profile analysis in static compression, uni- and bi-axial extension and gluten index. Bread crumb characteristics were studied by dynamic mechanical (DMA) and thermal analysis (TMA). Pearson correlation analysis provided a range of significant correlation coefficients (r) (from 0.48 to 0.82) for the relationships between dough static characteristics and bread dynamic and thermal properties. Negative relationships were found for thermo-mechanical bread properties (Eplt′andEf0′) and uni- and bi-axial dough extensional parameters (extensibility at rupture, strain hardening index and time of semirelaxation). Results indicate that dynamic and thermal viscoelastic parameters (f0,Ef0′andEplt′) obtained from fundamental rheological measurements have a significant role in monitoring fresh bread quality instead of the classical mimetic methods.

A dynamic and stationary rheological study of erythrocytes incubated in a glucose medium

A higher than normal glucose concentration in a suspending medium may produce non-enzymatic glycosylation of erythrocyte proteins. This process can modify the viscoelastic properties of erythrocytes. In this paper, we studied the possible relationship between glucose concentration in a suspending medium and erythrocyte rheological parameters. Human venous blood was obtained from the antecubital veins of 10 healthy volunteers. Blood samples were anticoagulated with EDTA and centrifuged. Red blood cells (RBCs) were washed and subsequently divided in aliquots, which were incubated in vitro with glucose solutions of different concentrations. Dynamic and stationary viscoelastic parameters of RBCs were determined by laser diffractometry in an Erythrodeformeter. Aggregate shape parameter (ASP) of the RBCs was determined by digital image processing. Significant changes were observed both in ASP and in rheological parameters when the glucose concentration in the medium was increased, demonstrating that a glucose concentration as low as 1% induces alterations in the mechanical properties of RBCs.

Effective volume changes during fatigue and fracture of polyacetal

AbstractConventional tensile dilatometry techniques are extended to cyclic fatigue applications to study volume changes that occur during controlled‐load cyclic fatigue of polyacetal. During fatigue, in‐situ measures of the irreversible and elastic volume change are monitored together with dynamic viscoelastic parameters (E′, E″, and Tan δ), and changes in the energy densities (strain energy, potential energy, and irreversible work). The results show that the effective irreversible volume of the polyacetal gradually increases over a wide range of applied cyclic stress. However, at high stress levels and/or frequencies (i.e., low‐cycle, thermally dominated regime), the effective Poisson's ratio of the polyacetal increases as it softens (evidenced by the dynamic viscoelastic data). Conversely, at lower stress levels, the Poisson's ratio continually decreases coincident with decreases in the loss modulus (E″) and the irreversible work density. These results are indicative of entirely different mechanisms governing the low‐cycle (high stress level) and high‐cycle (low stress) regimes. Also, comparisons between tensile and fatigue dilatometry studies show that the dilational‐strain response of samples fatigued at high stress levels are similar to data obtained from monotonic tensile dilatometry. However, the dilationstrain response of samples fatigued at lower stress levels are distinctly different from low‐cycle fatigue and tensile dilatometry.

Effects of processing on rheology and structure of double cream cheese

Double cream cheese curd was industrially made and post-treated in a pilot scale plant. After storage at 5 °C for 7–9 days, rheological properties of the intermediate and final products were measured using penetrometry, flow curves recording and dynamic testing. Results showed that the curds exhibited timedependent hysteresis of the flow properties and polymer-like dynamic viscoelastic behaviour, independently of the manufacturing stage. Curd mixing at 70 °C and 500 r.p.m. with salt and predenatured whey protein concentrate and dynamic cooling at 20 or 13 °C decreased firmness and dynamic viscoelastic parameters G′ and G″, while tan δ ( G″ G′ ) increased. There was a breakdown of the curd with a decrease in elastic deformation, typical of a solid material and a corresponding increase in viscous flow, characteristic of a liquid. On the other hand, evolution of the rheological parameters was the reverse after heat treatment at 85 °C and homogenization at 20 MPa (first stage) + 5 MPa (second stage). The curd structure was developed with a transition of behaviour to that typical of an elastic solid. Curd cooled dynamically to 13 °C became unstable during subsequent storage. This phenomenon was thought to result from an important breakdown of the curd during dynamic cooling and from aggregation of the milk fat globules during storage.