Time-temperature Superposition Research Articles

A general viscosity model for high moisture extrudates of pea protein isolates/gluten blend

A capillary pre-shearing rheometer, Rheoplast®, allowing for simulation of an extrusion process, was used to determine the viscosity of 60/40 pea protein isolate/gluten blends previously extruded at different temperatures (130 °C, 140 °C, 150 °C) and moisture contents (50%, 55%, 60% w/w). Electronic microscopy and mechanical testing showed that the materials displayed distinct anisotropic and fibrous structures. Pressure profiles were determined over an apparent shear rate range of 10–104 s−1, using capillary dies with length/diameter (L/D) ratios 8, 16, and 32 (D = 1 mm). For all materials, the pressure profiles are regular, suggesting the absence of wall slip. All flow curves could be fitted with the Ostwald–de Waele model. The values of consistency index (K), ranging from 480 to 5000 Pa.sn, and those of the flow index (n), from 0.25 to 0.7, were inversely correlated, reflecting the effect of material structuring. Furthermore, the time-temperature superposition principle was extended to account for the influence of water content by introducing the glass transition temperature (Tg) of the protein mixture with curve shift factors depending linearly on Tg/T. All results can then be fitted using a Carreau model, describing the viscous behavior within the range [1, 105 s−1] with plateau viscosity (η0) values varying between 240 and 1050 Pa.s. Finally, by extrapolating Bagley plots to L/D = 0, entry pressure was derived, and, consequently, apparent elongational viscosity was determined, leading to Trouton number values around 100. Results are interpreted by structural differences and the viscosity model can be used for computer simulation of flow in the die.

Viscoelastic and flow behaviour of β-lactoglobulin/lactoferrin coacervates: Influence of temperature and ionic strength.

Viscoelastic and flow behaviour of β-lactoglobulin/lactoferrin coacervates: Influence of temperature and ionic strength.

CONTRIBUTION OF CROSSLINK NETWORK STRUCTURE TO THE VISCOELASTIC CHARACTERISTICS OF EPDM: TUNING DYNAMIC PROPERTIES THROUGH HYBRID CURING

ABSTRACT EPDM is the fourth most widely used general-purpose elastomer, accounting for approximately 10% of total synthetic rubber production. With its broad applications in the automotive and construction industries, the analysis of EPDM’s dynamic viscoelastic properties is critical for optimizing product performance. Although the effects of various fillers and their structures on EPDM’s viscoelastic behavior have been widely studied, the impact of crosslink network architecture on long-term viscoelastic properties is seldom explored. To investigate the influence of different crosslink types and their compositions on the long-term viscoelastic behavior of EPDM, we have used thiol-amine analysis, time–temperature superposition for frequency-dependent properties, and temperature scanning stress relaxation. We establish correlations between crosslink features and the viscoelastic properties of carbon black–filled EPDM. In addition, we explore the effects of unique crosslink networks formed through hybrid cure systems containing accelerated sulfur and peroxide on the viscoelastic performance of EPDM. Our findings indicate that the frequency dependence of viscoelastic properties is governed by crosslink length, whereas temperature dependence is influenced by crosslink type. The results also indicated a strong correlation between plateau modulus and polysulfide crosslinks. These insights offer valuable guidance for optimizing the viscoelastic characteristics of next-generation elastomeric materials.

Roller Compacted Concrete for Road Base Layer with RAP and Steel Fibers: Viscous Properties and Description of Experimental Sites

A high-performance composite material consisting of reinforced compacted cement concrete including Reclaimed Asphalt Pavement (RAP) has been investigated. This composite material is used as a base layer in combination with an asphalt overlay for heavy traffic roads. Steel fibers are used to minimize crack opening. RAP is added to preserve raw material and to comply with sustainable development, especially in the case of in-situ treatments. Composites with different RAP and fiber content and cement content were studied both in laboratory and on site. The laboratory study is divided into two parts. First, classical standard tests for road concrete were carried out: compressive strength, compressive modulus and tensile splitting strength, with a view to the design of pavement structures to be used on site. Secondly, more comprehensive rheological tests, such as complex modulus and fatigue tests, were performed to obtain a better knowledge of material behavior. Then, on-site behavior was studied from two experimental sites. The presence of bitumen in cement-treated composites induces an increase of viscous properties, observed mainly on the phase angle. These composites respect the time-temperature superposition principle and can be fitted by a visco-elastic rheological model.

AN INVESTIGATION OF THE FLUOROSILICONE RUBBER THERMO-OXIDATION PROCESS AT HIGH TEMPERATURES

Abstract Fluorosilicone (FVMQ) rubber is commonly used in many military aircraft applications such as seals and gaskets due to its exceptional heat stability, low temperature flexibility and resistance to fuels and oil. In this investigation, a peroxide cured and silica filled FVMQ rubber compound was prepared and subsequently submitted to accelerated heat aging for up to 50 weeks at temperatures between 75 to 250°C. Heat aged samples were then tested for hardness, physical property characteristics and crosslink density by solvent swell and Double Quantum – Nuclear Magnetic Resonance (DQ NMR). The Arrhenius methodology was applied to the shifted experimental data assuming the principle of time-temperature superposition. The tensile strength and elongation at break both decrease upon thermal treatment. A small stiffness increase was observed by both the hardness and the tensile stress at 10% elongation test data. The characterization of the crosslink density by solvent swell testing was inconclusive. On the other hand, the DQ NMR testing clearly showed that the crosslink density decreases while the number of chain defects increases. The unaged crosslink distribution is heterogeneous in nature displaying much more heterogeneity than peroxide cured silicone. Non-linear Arrhenius behavior was observed between 75 to 250°C with a mechanism change at 175°C. The FVMQ crosslink distribution becomes more heterogeneous with aging. A significant loss of low molecular weight FVMQ due to depolymerization and backbiting reactions was observed at higher aging temperatures. Reactions with the silica surface also occurred with the creation of Si-O bonds. No direct evidence of thermo-oxidative and oxygenation reactions was observed. Reaction mechanisms have been proposed to explain the degradation of FVMQ due to heat aging.

Quantitatively Connecting Experimental Time–Temperature–Superposition–Breakdown of Polymers near the Glass Transition to Dynamic Heterogeneity Via the Heterogeneous Rouse Model

Quantitatively Connecting Experimental Time–Temperature–Superposition–Breakdown of Polymers near the Glass Transition to Dynamic Heterogeneity Via the Heterogeneous Rouse Model

Relaxation Modeling of Unidirectional Carbon Fiber Reinforced Polymer Composites Before and After UV-C Exposure

Carbon fiber-reinforced polymers (CFRPs) are widely used in aerospace for their lightweight and high-performance characteristics. This study examines the long-term viscoelastic behavior of CFRP after UV-C exposure, simulating low Earth orbit conditions. The viscoelastic properties of the polymer were evaluated using dynamic mechanical analysis and the time-temperature superposition principle on both unexposed and UV-C-exposed samples. After UV-C exposure, the polymer’s instantaneous modulus decreased by about 15%. Over a 32-year period, the modulus of the unexposed resin is expected to degrade to approximately 25% of its initial value, while the exposed resin drops to around 15%. These experimental results were incorporated into finite element method models of a unidirectional CFRP representative volume element. The simulations showed that UV-C exposure caused only a slight reduction in the CFRP’s axial relaxation coefficient along the fiber’s axis, with no significant time-dependent degradation, as the fiber dominates this behavior. In contrast, the axial relaxation coefficient perpendicular to the fiber’s axis, as well as the off-diagonal and shear relaxation coefficients, showed more notable changes, with an approximate 10% reduction in their initial values after UV-C exposure. Over 32 years, degradation became much more severe, with differences between the pre- and post-exposure coefficient values reaching up to nearly 60%.

Molecular-scale free volume and dynamic properties of a model ionomeric elastomer: Effect of curative systems

Cross-links significantly influence the chain packing efficiency and free volume in elastomeric materials, affecting their segmental dynamics. In this context, ionomeric elastomers serve as model systems that can undergo vulcanization through covalent and ionic cross-linking, enabling tuning their macroscopic properties. In this study, we investigate the effects of sulfur (covalent) and zinc oxide (ionic) cross-linking (with and without stearic acid) on the cross-link density, molecular-scale free volume, segmental relaxation and mechanical properties of carboxylated nitrile butadiene rubber (XNBR) networks by using a combination of analytical techniques including swelling studies, positron annihilation lifetime spectroscopy (PALS), dynamic mechanical analysis (DMA) and tensile testing. PALS measurements revealed a distinctive bimodal distribution of free-volume elements in the ionomeric networks, observed for the first time. This feature provided evidence of ionic aggregation-induced immobilization of polymer chains, which resulted in smaller free volume elements (1.5–2 Å) than in the bulk ionomeric matrix (3.0–3.5 Å). DMA studies revealed two segmental relaxations (α and α′) in the cross-linked elastomers, which could be tailored based on the cross-link density of the networks. The frequency-dependent DMA master curves, derived through time-temperature superposition, showed broad tan δ (loss factor) vs. frequency profiles for the networks with tan δ values exceeding 0.50, indicating their potential suitability for passive vibration damping applications. The ionically cross-linked networks exhibited superior mechanical properties compared to the networks prepared by covalent and mixed modes of curing.

Research on Tensile Stress–Strain Relationship of Azide Polyether Propellant for Wide‐Temperature Range Based on Time–Temperature Superposition Principle

ABSTRACTAzide polyether propellants are emerging high‐energy solid propellants and have broad application prospects. To determine their mechanical properties under wide temperature ranges, tensile tests were conducted considering different combinations of temperature and loading rate, and the corresponding tensile stress–strain curves were plotted. The influence laws of temperature and loading rate on the materials' tensile response were revealed through qualitative and quantitative analyses. The applicability of the time–temperature superposition principle to the nonlinear deformation stage of the propellant was proved, and a stress response prediction method derived from this principle that solely relies on dynamic mechanical analysis and tensile test data was established.

Multiaxial characterisation and nonlinear thermoviscoelastic isotropic and orthotropic constitutive models of ETFE membranes

Multiaxial characterisation and nonlinear thermoviscoelastic isotropic and orthotropic constitutive models of ETFE membranes

Prediction of the thermal degradation–induced colour change of acrylonitrile butadiene styrene products as a function of temperature and titanium dioxide content

Prediction of the thermal degradation–induced colour change of acrylonitrile butadiene styrene products as a function of temperature and titanium dioxide content

Study of Thermo‐Oxidative Aging of Fluorinated Gaskets (FKM) Used in Plate Heat Exchangers

AbstractGaskets are sealing elements used in plate heat exchangers, which are subjected to aggressive conditions during service. In particular, the compression state, together alongside temperatures, can cause a premature deterioration of properties. To monitor and prevent such a situation, this study uses the TTS (time‐temperature superposition) method and Arrhenius to predict the lifetime of FKM gaskets. For this purpose, thermo‐oxidative aging is conducted at different temperatures for up to 6 months, monitoring compression set (CS) and Shore A hardness. The results indicate that the gasket can withstand periods of up to almost 300 days in service for an operating temperature of 140 °C.

Study of the temperature-humidity equivalence and the time-temperature superposition principle in the finite-strain response of polyamide-6 and short glass fibre-reinforced polyamide-6

Study of the temperature-humidity equivalence and the time-temperature superposition principle in the finite-strain response of polyamide-6 and short glass fibre-reinforced polyamide-6

Thermodynamically consistent modeling of viscoelastic solids under finite strain

The present article is concerned with modeling the viscoelastic behavior of Polydimethylsiloxane (PDMS) in large-strain regime. Starting from the basic principles of thermodynamics, an incremental variational formulation is derived. Within this model, the free energy density and dissipation function determine elastic and viscous properties of the solid. The main contribution of this paper is the estimation of the parameters in the proposed phenomenological model from measurements conducted on Sylgard184 samples. This non-linear material model simplifies to a Prony-series representation in frequency domain in case of small deformations. The coefficients of this Prony-series are detected from dynamical temperature mechanical analysis measurements. Time-temperature superposition allows to combine measurements at different temperatures, such that a sufficiently large frequency range is available for subsequent fitting of Prony-parameters. A set of material parameters is thus provided. The incremental variational formulation directly lends itself to finite element discretization, where an efficient and stable choice of elements is proposed for radially symmetric problems. This formulation allows to verify the proposed model against experimental data gained in ball-drop experiments.

Experimental and Theoretical Analysis of Frequency- and Temperature-Dependent Characteristics in Viscoelastic Materials Using Prony Series

This study comprehensively investigates the frequency- and temperature-dependent viscoelastic properties of two elastomer materials, focusing on the comparison between experimental results and theoretical models derived from Prony series coefficients. Dynamic Mechanical Analysis (DMA) was performed across a broad temperature range of 0–100 °C and frequency range of 0.1–100 Hz to generate storage modulus and relaxation modulus data for both materials. Relaxation tests were conducted at 25 °C to further characterize the time-dependent behavior. Time–Temperature Superposition (TTS) was applied to the resultant shift factors used to fit both Williams–Landel–Ferry (WLF) and Arrhenius equations. Additionally, sinusoidal sweep tests were carried out at 0 °C, 25 °C, 50 °C, and 80 °C, with frequencies ranging from 1 Hz to 1000 Hz, to experimentally determine the natural frequencies of the elastomers. The findings demonstrate that Prony series coefficients derived from storage modulus data offer a more accurate prediction of the viscoelastic response and natural frequencies compared to those derived from relaxation modulus data. The storage modulus data closely match the experimentally observed natural frequencies, while the relaxation modulus data exhibit larger deviations, particularly at higher temperatures. The study also reveals temperature-dependent behavior, where increasing temperature reduces the stiffness of the materials, leading to lower natural frequencies. This comprehensive analysis highlights the importance of selecting appropriate modeling techniques and data sources, particularly when predicting dynamic responses under varying temperature and frequency conditions.

Engineering water-shut-off operations: Application of rheological time-temperature superposition approach for organically-crosslinked polymer gel systems

Engineering water-shut-off operations: Application of rheological time-temperature superposition approach for organically-crosslinked polymer gel systems

Predicting lifetime of adhesive bonds for naval steel by time-temperature superposition

Predicting lifetime of adhesive bonds for naval steel by time-temperature superposition

Study on the composition and properties of EME-SBS-Nano ZnO high modulus asphalt material

The objective of this research is to address the rut problems in asphalt pavements and to resist the permanent plastic deformation with the increasing heavy traffic loads. In this paper, a new type materials of high modulus asphalt was developed by incorporating styrene–butadiene–styrene (SBS) and zinc oxide nanoparticles (nano ZnO) with an (EME)-type high modulus modifier, guided by the synergistic effects and the preparation methods of High-speed shear. The basic road performance, mechanical response and thermal stability of the new high modulus asphalt materials were analysed through basic physical indicator tests, dynamic shear rheometer tests, thermogravimetric analysis (TGA), the time–temperature superposition principle, the Refutas model, and the Christensen-Andersen-Marasteanu model. The optimal results demonstrate that the optimal blend ratio of the developed asphalt is 12% EME/8% SBS/1.5% ZnO. Under this composition, the road performance indicator values of softening point, penetration and ductility of the modified asphalt met the standard requirements. The dynamic shear rheometer tests demonstrates that the inclusion of SBS and nano ZnO considerably enhanced the shear resistance and recovery deformation capacity of EME, effectively improving the high-temperature deformation resistance of asphalt. Furthermore,the Refutas and the Christensen-Andersen-Marasteanu model fitting results showed that adding SBS and nano ZnO considerably improved the temperature sensitivity of the EME types high modulus modified asphalt and exhibiting low frequency sensitivity. Compared to PR Module-type high modulus modifier(PRM),TGA reveals that the maximum thermal weight loss of EME-SBS-ZnO decreased by 3.5441%, indicating better thermal stability and the major character of SBS,EME and asphalt is physical reaction. Moreover, EME-nano ZnO-SBS high modulus asphalt at 64 °C shows Jnr-diff = 9.5% and passes the "E" extreme traffic grade. Additionally, its cost is 4.67% lower than that of the PRM high modulus modified asphalt, presenting considerable economic benefits.

Rheology and aging of amine functionalized polyolefins

The time dependent rheo-mechanical properties of a class of associating polymers (amine-functionalized polyolefins) are investigated using rheology, differential scanning calorimetry (DSC), infrared microscopy, and small-angle x-ray scattering (SAXS) measurement. The modulus of the sample increases with time and temperature as determined by shear rheology. With higher temperature and longer equilibration time, there is a gradual decrease in the power-law scaling of storage and loss moduli in the terminal flow region and the emergence of an additional low-frequency plateau in the storage modulus. The aging behavior at different temperatures is found to be correlated with the horizontal shift factors obtained from the time-temperature superposition. With increasing aging time, there is an increase in the glass transition temperatures (DSC), and a continuous red shift in the associated amine stretching peak (Fourier-transform infrared). SAXS also shows the emergence of a dominant microstructure after aging of the sample for a long time. Based on the characterization results, an underlying microscopic origin of the aging process is proposed.

Compositional dependence of electrochemical properties in biopolymer blend-based solid electrolytes doped with sodium perchlorate for EDLC applications

Biopolymer-based blends of solid electrolytes capable of conducting sodium ions were prepared via solution casting by incorporating sodium carboxymethyl cellulose (NaCMC) and polyvinyl alcohol (PVA) with varying concentrations of sodium perchlorate monohydrate (NaClO4.H2O), which was used as the dopant. The prepared electrolytes were characterized to reveal their structural, vibrational, electrical, and electrochemical properties that make them promising as solid polymer electrolytes (SPEs). X-ray diffraction (XRD) analysis showed that the amorphous nature of the sample increased with the addition of NaClO4.H2O salt concentrations of up to 30 wt.%. The complexation between the polymers and salt was confirmed by Fourier-Transform Infrared (FTIR) analysis. The SPE exhibited an optimal ionic conductivity of (1.90 ± 0.05) ×10−5 S cm−1, which is three orders higher than that of the pristine polymer blend with (5.31 ± 0.61) ×10−8 S cm−1, as determined by electrochemical impedance spectroscopy (EIS) analysis. Scaling studies conducted based on AC conductivity and tangent loss revealed that these measurements could be represented by a single master curve, which suggests that the optimal sample adheres to the time-temperature superposition principle (TTSP). The temperature dependence of Jonscher's exponent indicates that the conduction mechanism can be effectively represented by the Quantum Mechanical Tunneling model (QMT). Both transference number measurement (TNM) and linear sweep voltammetry (LSV) analyses validated the electrolyte's suitability for energy device applications by demonstrating its high ion transference number and electrochemical potential window of 3.93 V. The optimized SPE film was subsequently utilized in an electrochemical double-layer capacitor (EDLC) device to evaluate its performance as both an electrolyte and separator. The supercapacitor exhibited an impressive energy density of 15.18 Wh kg−1 and a power density of 4512.5 W kg−1, along with remarkable stability in terms of cycle life.