Dynamic Viscoelasticity Research Articles

Investigation of Dynamic Viscoelastic Asymmetric Response of PA6 Film Based on Fractional Rheological Model.

Polyamide 6 (PA6) film as a typical viscoelastic material, satisfies the time-temperature superposition (TTS), and demonstrates obvious dynamic strain amplitude and frequency correlation under dynamic load. The investigation of the dynamic mechanical behavior of PA6 film is essential to ensure the safety of these materials in practical applications. In addition, dynamic mechanical property testing under conventional experimental conditions generally focuses on the short-term mechanical performance of materials. Therefore, the dynamic viscoelasticity of PA6 film was tested using a dynamic thermo-mechanical analyzer (DMA) in this study, and the complex modulus master curve was constructed based on time-temperature superposition (TTS) to realize the accelerated characterization of long-term mechanical properties. Furthermore, according to experimentally obtained asymmetric characteristics of the Cole-Cole diagram and the loss modulus master curve of the PA6 film, the parameter distribution of the fractional Zener model and the modified fractional Zener model were compared, and the asymmetric dynamic viscoelastic response of PA6 film under different conditions was systematically investigated using these models. The results indicate that the modified fractional Zener model can truly describe the dynamic asymmetric characteristics of PA6 film, verify the feasibility and advantages of the modified fractional rheological model, and provide some theoretical guidance for exploring the tensile rheological mechanism of PA6 film.

Establishment and evaluation of dynamic viscoelasticity constitutive model for asphalt mixtures based on PCA model: Utilizing coal-based synthetic natural gas slag and phosphogypsum whisker as substitute fillers

To promote the secondary utilization of solid waste in asphalt pavement and reduce resource waste and environmental damage, the fine solid waste powder from the secondary treatment of solid waste was used as a substitute filler to prepare asphalt mixtures. To more precisely characterize the effects of filler type and substitution ratio on the dynamic viscoelastic mechanical characteristics of asphalt mixtures, the dynamic modulus test was conducted on asphalt mixtures, while the dynamic modulus master curve of asphalt mixtures was established based on the time-temperature equivalent principle and the Sigmoidal function. The improved generalized Sigmoidal (IGS) model, five-parameter fractional Zener (FFZ) model, six-parameter fractional Zener (SFZ) model and ten-parameter fractional Zener (TFZ) model were used to construct the shrinkage frequency curves of different asphalt mixtures under different constitutive relationships, whereas the applicability of the constitutive models was further evaluated by the principal component analysis (PCA) model. The research results showed that the dynamic modulus and phase angle of the mixture exhibited a similar change rule with the variation of temperature and frequency, and the use of solid waste-based fillers could effectively reduce the effect of frequency variation on the viscoelasticity of the mixture. The dynamic modulus master curve constructed by Sigmoidal function could accurately describe the functional relationship between the dynamic modulus with loading frequency and temperature, and the variation trend of dynamic modulus in a wider frequency range was flattened with the increase in frequency, and this change rule was not affected by the substitution ratio of the filler, while the use of solid waste-based filler could reduce the dependence of the mixture on the temperature. Compared to several fractional constitutive models, the IGS model exhibited a higher fitting accuracy for the dynamic viscoelasticity of several mixtures, and with the use of solid waste-based fillers, the deviation of fitting curves gradually decreased. A comparative study showed that the fractional constitutive model was difficult to accurately describe the dynamic viscoelasticity of the mixture, and the IGS model was preferred to be recommended as a calculation model to investigate the constitutive relationship on the dynamic viscoelasticity of the mixture.

Rheological Behavior of an Aqueous Suspension of Oxidized Carbon Nanohorn (CNHox).

Oxidized carbon nanohorn (CNHox) a carbon nanomaterial that has attracted attention due to its unique material properties. It is expected to be applied in various areas like cancer treatment, gene-expression technology, fluids with high thermal conductivity, lubricants, and so on. While the rheological measurements of suspensions provide information on the effective size and interactions of suspended particles, the rheological behaviors of aqueous suspensions of CNHox have never been systematically investigated. To clarify the rheological behaviors of aqueous suspensions of CNHox, their viscosity and dynamic viscoelasticity were measured with changing particle concentration and salt concentration. The viscosity of a CNHox suspension showed yield stress at low shear rates and showed shear-thinning behavior with increasing shear rates. The viscosity of 5 weight % CNHox suspensions was comparable to that of 60 weight % silica suspensions. This high viscosity at a low CNHox concentration is probably due to the porous structure and large effective volume of the CNHox particle. The estimated effective volume of CNHox calculated by the Krieger-Dougherty equation was 18.9 times larger than the actual volume calculated by the mass concentration and density. The dependence of rheological behavior of the CNHox suspension on salt concentration was weak compared to that of the colloidal silica suspension. This weak dependence on salt concentration may be due to the roughness of the particle surface, which would weaken the effect of electric double-layer interactions and/or van der Waals interactions between particles. These rheological behaviors of the aqueous suspension of CNHox shown in this research will be useful in efforts to improve the efficiency of its utilization for the various applications.

Machine learning-combined rheological and structural characterization of starches for enhanced melt-stretch features in plant-based cheese analogues

The global demand for plant-based food products, including cheese analogues, is continuously increasing. However, most scientific attention has focused on their nutritional value rather than on functional properties such as melt-stretch. This study integrated the rheological features (pasting and viscoelasticity) of nine different starches with machine learning analysis to identify melt-stretchable starches. These starch samples were further evaluated in the formulation of plant-based cheese analogues. Hydroxypropyl tapioca, waxy potato, and tapioca starches showed the highest melt-stretch length values, compared to the other starch samples. The melt-stretch properties of the starch samples did not show distinct correlations with their individual pasting parameters, while they had lower viscoelasticity as well as high frequency dependence. FTIR analysis demonstrated that the decreased ratio of crystalline to amorphous regions upon conversion to a paste state contributed to the melt-stretch properties of starches. When the pasting and viscoelastic results were subjected to machine learning analysis, the starch samples were well-clustered based on their melt-stretchability. Furthermore, the starch samples with good melt-stretchability (hydroxypropyl tapioca, waxy potato, and tapioca starches) were successfully identified by the logistic binary classification model trained using rheological datasets, specifically, dynamic viscoelasticity. Similar melt-stretch features were moreover observed in the starch-incorporated plant-based cheese analogues, confirmed by a distinct decrease in the storage moduli over temperature and the highest values of melting index.

Natural Rubber/Styrene-Butadiene Rubber Blend Composites Potentially Applied in Damping Bearings.

Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were prepared via the conventional mechanical blending method. The effects of the rubber components on the compression set, compression fatigue temperature rising and the thermal oxidative aging properties of the NR/SBR blend composites were investigated. Meanwhile, the dynamic mechanical thermal analyzer and rubber processing analyzer were used to characterize the dynamic viscoelasticity of the NR/SBR blend composites. It was shown that, with the increase in the SBR ratio, the vulcanization rate of the composites increased significantly, while the compression fatigue temperature rising of the composites decreased gradually from 47 °C (0% SBR ratio) to 31 °C (50% SBR ratio). The compression set of the composites remained at ~33% when the SBR ratio was no more than 20%, and increased gradually when the SBR ratio was more than 20%.

A Hybrid Stress Finite Element Method for Integro-Differential Equations Modelling Dynamic Fractional Order Viscoelasticity

A Hybrid Stress Finite Element Method for Integro-Differential Equations Modelling Dynamic Fractional Order Viscoelasticity

Sucrose and Ca2+ synergistically regulate the rheological properties of apple high-methoxyl pectin

The thickening and gelling mechanism of high-methoxyl pectins (HMPs) with different degree of esterification (DE) values (60.6 %, 66.1 %, and 72.4 %) synergistically affected by calcium ion (Ca2+) and sucrose was investigated using several technical methods. Rheological measurements, including steady-shear flow, thixotropy and dynamic viscoelasticity tests, texture analysis, water-holding capacity (WHC), thermal analyses (TG), and microstructure observation (TEM), were all systemically conducted. The results showed that the main thickening and gelling mechanism of Ca2+ on different HMPs was complex and the presence of sucrose had a synergistic effect on structure formation in HMP systems. Ca2+ was not always conducive to structure formation, and excessive Ca2+ addition may hinder structure formation. HMP systems with lower DE values had higher gel strengths due to the presence of more binding domains. The results of the texture properties, WHC, and thermal characteristics coincided with those obtained from the rheological measurements, which reflect the variations in HMPs affected by Ca2+ and DE. All of these results showed that Ca2+ addition at an appropriate concentration in the presence of sucrose favors HMP gelation even in the absence of acid. The results obtained here are expected to broaden the application of HMPs in acid-free gel food products.

Preparation and energy absorption of flexible polyurethane foam with hollow glass microsphere

This paper presents the preparation of a partially open-cell and partially closed-cell flexible polyurethane foam material (flex-PUF), which exhibits improved cushioning performance compared to conventional protective materials. Hollow Glass Microspheres (HGM) were used as a filling material to enhance the compressibility of the material. In order to investigate the effects of HGM on the multi-impact protection and vibration damping performance of flex-PUF with different thicknesses, flex-PUF samples filled with varying volume fractions of HGM were subjected to multi-impact testing and dynamic viscoelasticity experiments. The destructive mechanism of HGM under impact was observed using scanning electron microscopy (SEM). The experimental results revealed that, under the same impact energy conditions, filling flex-PUF with HGM reduced the maximum impact displacement while enhancing energy absorption, although at the expense of cushioning performance. As the number of impact increases, the stiffness of flex-PUF decreased. In the vibration experiments, as the frequency increased, the proportion of flex-PUF’s viscous damping energy dissipation decreases.

Surfactant-mediated gelation by 12-hydroxyoctadecanoic acid in a nonionic surfactant system

In this study, we present a hydrogel fabrication utilizing a water-insoluble, low-molecular-weight organogelator by the surfactant-mediated gelation (SMG). Specifically, we employed a nonionic surfactant (poly(oxyethylene) sorbitan monooleate, Tween 80) and an organogelator (12-hydroxyoctadecanoic acid, 12-HOA) to produce hydrogels. Gelation experiments conducted at varying concentrations of surfactant and gelator demonstrated successful hydrogel formation in the water/Tween 80/12-HOA system. Moreover, we observed a significant dependence of surfactant concentration on gelation ability. The sol-gel transition temperature was found to be influenced by both the gelator and surfactant concentrations. Optical and electron microscopy analyses revealed that the SMG hydrogels comprised an entangled network of fibers with micrometer-scale widths, formed as bundles of submicron-wide fibers, and further composed of fine fibers measuring several tens of nanometers in width. These fine fibers exhibited a left-handed helical structure. Small- and wide-angle X-ray scattering corroborated the presence of a lamellar structure within the fine fibers, displaying a triclinic subcell morphology. The coexistence of micelles with the fiber network was confirmed through small-angle neutron scattering and UV–vis spectroscopy. Furthermore, dynamic viscoelasticity tests demonstrated that the SMG hydrogels exhibited typical solid-like properties indicative of gel behavior.

Effect of hydrothermal treatment on the rheological properties of xanthan gum

In this study, the effect of hydrothermal treatment with different temperatures (120–180 °C) on the rheological properties of xanthan gum was evaluated. When the temperature of hydrothermal treatment was relatively low (120 °C), the rheological properties of the hydrothermally treated xanthan gum was similar to the untreated xanthan gum (pseudoplastic and solid-like/gel-like behavior). However, as the temperature of hydrothermal treatment was higher, the rheological properties of the hydrothermally treated xanthan gum changed greatly (e.g., a wider range of Newtonian plateaus in flow curves, existence of a critical frequency between the storage modulus (G') and the loss modulus (G") in the dynamic viscoelasticity measurement, variation of complex viscosity). Although the hydrothermal treatment showed little influence on the functional groups of xanthan gum, it altered the micromorphology of xanthan gum from uneven and rough lump-like to thinner and smoother flake-like. In addition, higher concentration (2 %) of hydrothermally treated xanthan gum made its viscosity close to that of the untreated xanthan gum (1 %). Besides, hydrothermal treatment also affected the effect of temperature and salt (CaCl2) adding on the rheological properties of xanthan gum. Overall, this study can provide some useful information on the rheological properties of xanthan gum after hydrothermal treatment.

Discontinuous Galerkin finite element method for dynamic viscoelasticity models of power‐law type

AbstractLinear viscoelasticity can be characterized by a stress relaxation function. We consider a power‐law type stress relaxation to yield a fractional order viscoelasticity model. The governing equation is a Volterra integral problem of the second kind with a weakly singular kernel. We employ spatially discontinuous Galerkin methods, symmetric interior penalty Galerkin method (SIPG) for spatial discretization, and the implicit finite difference schemes in time, Crank–Nicolson method. Further, in order to manage the weak singularity in the Volterra kernel, we use a linear interpolation technique. We present a priori stability and error analyses without relying on Grönwall's inequality, and so provide high quality bounds that do not increase exponentially in time. This indicates that our numerical scheme is well‐suited for long‐time simulations. Despite the limited regularity in time, we establish suboptimal fractional order accuracy in time as well as optimal convergence of SIPG. We carry out numerical experiments with varying regularity of exact solutions to validate our error estimates. Finally, we present numerical simulations based on real material data.

Postharvest ripening of newly harvested corn: Weakened interactions between starch and protein

The effects of postharvest ripening of corn on the mechanisms of starch and protein interactions were investigated using molecular dynamics and several chemical substances. Sodium dodecyl sulfate (SDS) treatment all significantly affected the starch content, molecular weight of proteins, relative crystallinity, pasting characteristics and dynamic viscoelasticity in samples before and after postharvest ripening. In the corn that had not undergone postharvest ripening, there were also significant electrostatic interactions and hydrogen bonds between starch and protein. In addition, molecular dynamics had demonstrated that the forces between starch and protein in corn were mainly hydrophobic interactions, electrostatic interaction, and hydrogen bonds. Compared with zein, corn glutelin was more tightly bound to starch. The binding energy of starch to both proteins was reduced in after postharvest-ripened corn. This study laid a rationale for investigating the change mechanism of corn postharvest ripening quality and improving processing property and edible quality of corn.

Correlating dynamic relaxation and viscoelasticity in metallic glasses

Correlating dynamic relaxation and viscoelasticity in metallic glasses

Study on the mobility control ability of a quaternary ammonium salt active polymer for oil flooding

Mobility control ability is an important property of polymer used in oil displacement. This work initially investigates the temperature and salt resistance, steady-state rheology, dynamic viscoelasticity, and long-term stability of a quaternary ammonium salt active polymer (AM/AMPS/DMCA). Subsequently, an examination was conducted to evaluate the static adsorption ability of AM/AMPS/DMCA on the surface of quartz sand, as well as the dynamic retention property within cores. Finally, the mobility control ability and oil displacement capacity of AM/AMPS/DMCA under various injection conditions was investigated in this study. The findings illuminate the superior attributes of AM/AMPS/DMCA, including its remarkable temperature and salt endurance, alongside its long-term stability, presenting a significant advancement over traditional binary polymers like AM/AMPS. Notably, AM/AMPS/DMCA exhibits a predominantly elastic modulus, which enhances its movement and deformation inside porous media. Furthermore, it has been shown that the resistance factor and residual resistance factor achieved by the 2000 mg/L AM/AMPS/DMCA solution in the core of 96.6 mD were 184.50 and 46.95, respectively. The enhanced oil recovery (EOR) value of 0.6 PV of AM/AMPS/DMCA achieved 30.48% in the core of 588.8 mD. This study not only demonstrates the capability of AM/AMPS/DMCA in EOR but also facilitates the understanding of the mobility control mechanism of polymers in porous media, offering valuable empirical guidance for the field application of polymers.

Self-assembling and foaming properties of nonionic, cardanol-based surfactants in aqueous solutions

Surfactants from renewable sources have gained attention due to their potential as substituents for petroleum-based chemicals. In this sense, surfactants based on cardanol, a compound abundant in the cashew nutshell liquid, have been proposed as suitable candidates for this purpose. However, their application is hindered by the lack of quantitative and reliable information about their bulk and surface properties in aqueous solutions. In this work, for the first time, three nonionic, cardanol-derived surfactants (7EO, 9EO, and 12EO), with different number of ethylene oxide (EO) units in the polar headgroup, had their foaming performances analyzed and correlated with their respective surface (equilibrium and dynamic surface tension and surface viscoelasticity) and bulk (cloud points, critical micelle concentration, micelle diameter, and viscosity) properties. Depending on the EO number, different scenarios were seen. Solutions containing the 7EO surfactant were below the cloud point at room temperature and presented antifoaming properties. Aqueous solutions of 9EO and 12EO displayed foamability comparable to solutions prepared with a traditionally employed anionic surfactant (sodium dodecyl sulfate, SDS) at the same concentrations. The surfactant 12EO presented a rapid surface adsorption, thus favoring the formation of large amounts of foam during aeration. Furthermore, solutions of 9EO resulted in foams that were considerably more stable than the ones formed by SDS. Such an enhanced stability was attributed to the presence of elongated micelles, formed at the vicinity of the cloud point, that increased solution viscosity and delayed the liquid drainage in the foams. This surfactant also promoted the formation of highly viscoelastic surface films that contributed to foam stabilization. The obtained results suggest that these surfactants can be used in the formulation of new products with a more sustainable character and with improved properties. Moreover, they indicate the important interchange among bulk aggregates, surface properties and foam stability in aqueous surfactant systems.

Effects of Laminaria japonica polysaccharide and coumaric acid on pasting, rheological, retrogradation and structural properties of corn starch

The aim of this study was to investigate the effects of Laminaria japonica polysaccharide (LJP) and coumaric acid (CA) on pasting, rheological, retrogradation and structural properties of corn starch (CS). Rapid viscosity analysis (RVA) revealed that LJP significantly increased the peak viscosity, trough viscosity, final viscosity, and setback viscosity of CS gel (p < 0.05) in a concentration-dependent manner. The addition of LJP and CA simultaneously caused the pasting of CS to need a greater temperature (from 75.53 °C to 78.75 °C), suggesting that LJP and CA made CS pasting more difficult. Dynamic viscoelasticity measurements found that all gels exhibited typical characteristics of weak gel. When compared to CS gel, 4 % LJP increased the viscosity and fluidity of gel and the simultaneous addition of LJP and CA reduced the elasticity. The steady shear results showed that the all gels were pseudoplastic fluids with shear-thinning behavior. In the meanwhile, the addition of LJP and CA enhanced the pseudoplasticity of CS-LJP-CA gel and improved its shear thinning. Furthermore, thermodynamic results showed that 8 % LJP promoted the retrogradation of CS gel and 2.0 % CA delayed the retrogradation of CS gel. Notably, on the 7th day of retrogradation, 2.0 % CA significantly decreased the retrogradation rate of CS-LJP by 19.31 % as compared to CS + 8 % LJP. Microstructure observation revealed that LJP made the honeycomb network structure of CS gel partially collapsed, and the surface of CS-LJP gel developed venation. Nevertheless, the structure of CS-LJP gel was clearly enhanced by adding CA. FT-IR spectra demonstrated that the addition of LJP or CA to CS did not result in the formation of a new distinctive peak in the system, suggesting the absence of a new group. Moreover, LF-NMR findings showed that LJP and CA strengthened the gel structure of CS and enhanced its capacity to retain water. This study not only provided a new insight into using LJP and CA to regulate the gel properties of CS, but also provided scientific strategy for developing starchy foods.

Effect of a Photolithography Polymer Mask's Dynamic Viscoelasticity on Microchannel Cross-Sectional Shapes of Glass Processed by Micropowder Blasting.

In this study, a micropowder blasting system with varying processing temperatures was proposed to control the cross-sectional shape of a channel processed on a glass substrate. Based on an analysis of the processing temperature-dependence of the dynamic viscoelastic properties of a commercial mask material for micropowder blasting, a processing temperature control system that can be installed in a micropowder blasting machine was designed. The erosion of the mask during micropowder blasting depended on the loss tangent in dynamic viscoelasticity, and showed a maximum value at a processing temperature of 100 °C. Moreover, we confirmed that the maximum decrease in the width of the processed microchannel was 30 µm (12%) by mask erosion, and this change was large compared with the maximum change in the thickness of the eroded mask. These results clarified that varying the processing temperature using a mask could control the cross-section of the processed line pattern profile on glass, and a small-width channel was realized at a processing temperature of 109 °C.

Viscoelasticity modeling of clay minerals by dynamic viscoelasticity measurement and its implications for earthquake faulting

Slip on clay fault planes at shallow depths in the seismogenic zone could be controlled by their rheology as well as their frictional properties; however, the rheological nature of clay faults is still an open question. Investigating the rheological properties of clay minerals is essential for understanding and modeling shallow earthquake faulting. Here, we perform dynamic viscoelasticity measurements on three clay minerals, namely kaolinite, illite, and smectite, wetted with water using a custom-made high pressure, high temperature rheometer. Our results confirm that the rheological properties resulting from the microstructure of clay minerals depend on the oscillation frequency, oscillation amplitude, temperature, and amount of water contained. In addition, the rheological properties vary systematically with the type of clay mineral. This suggests that the viscoelastic behavior of earthquake faults varies with the type of clay minerals present.

NON-STATIONARY WAVES IN A FUNCTIONALLY GRADED VISCOELASTIC PLANE-PARALLEL LAYER2

The propagation of nonstationary disturbances in a plane-parallel layer of infinite extent, which arise as a result of normal dynamic loading of one of its surfaces when the other surface is stationary, is investigated. The material of the layer is assumed to be functionally graded and, at the same time, viscoelastic. The hereditary properties of such a material are taken into account using linear integral Boltzmann–Volterra relations with regular kernels in the form of partial sums of the Prony's series. The peculiarity of this work is that here the parameters of the relaxation kernels are considered continuous functions of the transverse coordinate in the same way as other physical and mechanical characteristics. A method was used for the study, which consists in replacing a functionally graded material with an approximating layered homogeneous structure with continuity conditions at the contact of homogeneous layers. The solution of the nonstationary dynamic linear viscoelasticity problem for a package of plane homogeneous viscoelastic layers is presented in a special form, which greatly simplifies its numerical implementation, especially with a large number of layers with different hereditary properties. This made it possible to successfully apply this method and carry out a series of calculations using an efficient algorithm. Transient wave processes are investigated in the case when the parameters of a functionally graded material are non-monotonic functions of the transverse coordinate, symmetrical with respect to the middle surface of the layer. A comparison of transient wave processes for different types of these functions is carried out. The convergence of the calculation results with an increase in the number of approximating homogeneous layers with a continuous dependence of the external load on time is confirmed. The significant influence of both heterogeneity and viscosity of the material on nonstationary wave processes has been established.

Preparation and properties of shape memory polyurethane filaments triggered by human body temperature

To utilize the human body heat to trigger the shape memory smart textiles, shape memory polyurethane filaments (SMPUF) with three different transition temperatures were prepared based on modified polycaprolactone diol (PCL) by dry spinning. The chemical structure was characterized systemically. The shape memory properties, tensile properties, resilience, and viscoelasticity were studied comprehensively. The results revealed that the phase transition temperatures were close to human body temperature which measured 19.97°C, 27.33°C, and 30.37°C, respectively. Additionally, the fraction of hydrogen bonds in the samples was about 30% less than that of polyurethane filaments (PUF). The best shape fixity ratio was 88.5% and the shape recovery ratio was 96.7% belonging to samples with a transition temperature of 30.37°C. At 55°C, the elastic recovery was 45.2% higher than that at 22°C. As the temperature rose, the elastic modulus of SMPUF decreased until it reached that of PUF. The static and dynamic viscoelasticity of SMPUF indicated that the phase transition of the soft segment affects the movement of the molecular chain. SMPUF can be used as compression garments, and wearable orthopedic devices, such as the elastic bands prepared in this work.