Dynamic Viscoelastic Behavior Research Articles

Dynamic viscoelastic properties of ultra-large particle size asphalt mixture based on fractional derivative constitutive model

The aim of this paper was to accurately grasp and precisely characterize the dynamic viscoelastic properties of Ultra-Large Particle Size Asphalt Mixture (LSAM-50), and fully explore the features and simplified forms of the generalized fractional derivative Zener (GFDZ) model. The constitutive relations of the GFDZ model with n Abel elements were first given, and a modified GFDZ (mGFDZ) model was proposed. Then the master curves of LSAM-50, AC-13 and AC-20 mixtures were constructed, and the expression effects of different models and the dynamic viscoelastic behaviors of different asphalt mixtures were compared. The results showed that LSAM-50 was a typical viscoelastic material similar to traditional mixture. Both dynamic modulus and energy storage modulus decreased with increasing temperature. The phase angle increased first and then decreased with temperature increasing, and the peak value appeared near 40℃ at low frequency. The loss modulus increased first and then decreased with the temperature increasing. When the loading frequency was 0.1 Hz∼25 Hz, the peak value appeared at 0℃∼20℃. The rutting factors of LSAM-50 became larger with temperature reduction and frequency enhancement. When the number of Abel elements reached 2 in the GFDZ model or reached 3 in the mGFDZ model, the model fitting effects would no longer change significantly. The 2-mGFDZ model with only 5 parameters fitted master curves data satisfactorily and the physical meanings of parameters were clear. Comparing among three mixtures, LSAM-50, with the lowest asphalt content, showed significantly superior elasticity and better deformation resistance at medium and high temperatures. At low temperatures, the viscosity behavior of LSAM-50 was slightly inferior, but it may have pronounced plate properties considering the effect of aggregate skeletonization. The research results would promote new pavement structural design and mechanical response analysis.

Oleic acid-induced changes in the dynamic viscoelastic behavior of poly(methyl methacrylate) polymer film

This study investigates the impact of oleic acid on the dynamic viscoelastic behavior of polymethyl methacrylate (PMMA) polymer films. By incorporating oleic acid as a plasticizer, we aim to enhance the ductility and reduce the brittleness of PMMA. Dynamic mechanical analysis (DMA) was employed to assess changes in viscoelastic properties, revealing significant improvements in the flexibility and energy dissipation capacity of the PMMA films. The addition of oleic acid resulted in a noticeable shift in the glass transition temperature and a reduction in storage modulus, indicating enhanced polymer chain mobility. Raman and infrared spectroscopy confirmed the successful integration of oleic acid, highlighting its interaction with PMMA at the molecular level. Our findings demonstrate that oleic acid is an effective plasticizer for PMMA, providing valuable insights into the design of flexible and durable polymer-based materials for various applications.

Dynamic Viscoelastic Properties of Kenaf Fiber Reinforced Shape Memory Polymer Composites

This paper comprehensively investigates the dynamic viscoelastic behavior of shape memory polymer composites (SMPCs) reinforced with different weight percentages of kenaf fiber (KF) ranging from 0%, 5%, 10%, 15%, 20%, 30% and 40%. The dynamic mechanical behavior of these composites was characterized using dynamic mechanical analysis (DMA) over a range of temperatures. The objective was to determine the optimal fiber content of KF as reinforcement in SMPCs, specifically on viscoelastic response, storage modulus, loss modulus, damping and glass transition behaviour. The results revealed a clear correlation between the KF contents and the dynamic mechanical properties of SMPCs. The storage modulus significantly improves at higher KF content, particularly at elevated temperatures. Additionally, a quantitative assessment of coefficient C demonstrates strong interfacial bonding between fibers and the matrix in samples 30KF and 40KF. These samples also exhibit higher loss modulus and lower tan delta values, providing evidence for the efficacy of KF in enhancing composite properties. Moreover, higher KF contents induce a shift in the glass transition temperature, signifying enhanced in fiber-matrix interaction and thermal stability. The Cole-cole further demonstrates that at higher KF content, the sample surpasses Neat SMPU, presenting compelling evidence of improved matrix-fiber bonding. Statistical analysis through one-way analysis of variance (ANOVA) substantiates the statistical significance of the dynamic mechanical properties across the different weight percentages of KF-SMPCs. Based on these findings, 30KF is the optimal fiber content, balancing mechanical enhancement and feasible fabrication. This decision is grounded in challenges encountered at 40KF, where ensuring composite homogeneity becomes complex. This study contributes to the growing body of knowledge on utilization of natural fibers in development of advanced polymer composites while maintaining eco-sustainability.

Impact of Washing with Antioxidant-Infused Soda-Saline Solution on Gel Functionality of Mackerel (Auxis thazard) Surimi.

Mackerel (Auxis thazard), a tropical dark-fleshed fish, has the potential to be used in the production of surimi. It is necessary to identify the optimal washing method to make better use of this species since efficient washing is the most important step in surimi processing to ensure maximal gelling and high-quality surimi. The purpose of this study was to evaluate the combined effect of cold carbonated water (CW) with NaCl and antioxidants in washing media, so-called antioxidant-infused soda-saline solution, on lipid and myoglobin removal efficacy, biochemical characteristics, gelling properties, sensory features, and the oxidative stability of mackerel surimi in comparison with unwashed mince (T1) and conventional water washed surimi (T2). Mackerel mince was washed with CW in the presence of 0.6% NaCl at a medium to mince ratio of 3:1 (v/w) without antioxidant (T3) or with the addition of 1.5 mM EDTA plus 0.2% (w/v) sodium erythorbate and 0.2% sodium tripolyphosphate (T4), 100 mg/L gallic acid (T5), and 5 mM citric acid containing 8 mM calcium chloride (T6). During the first washing cycle, the antioxidants were mixed into the washing medium. The second and third washing cycles were then completed with cold water. The yields of all treatments were roughly 75-83%, based on the gross weight of the raw mince. The pH of the surimi was in a range of 5.47-6.46. All of the surimi had higher reactive sulfhydryl (SH) content and surface hydrophobicity but lower Ca2+-ATPase activity than unwashed mince (p < 0.05). After washing, lipids decreased significantly (p < 0.05), accounted for a 65-76% reduction. The T2 surimi had the highest peroxide value (PV). T1 had the lowest conjugated diene value. T1 and T4 surimi had the lowest TBARS value (p < 0.05). A lower non-heme iron level was found in all antioxidant-treated samples than in T1. Washing can increase the redox stability of myoglobin regardless of the washing media, as seen by the relatively low metmyoglobin levels. According to the dynamic viscoelastic behavior, all surimi and unwashed mince underwent the same degree of sol-gel transition following heat gelation. T1 showed the lowest breaking force, deformation, gel strength, and whiteness (p < 0.05). Surimi made from T4 or T5 had the highest gel strength when both breaking and deformation were considered, but the latter's expressible drip was noticeably higher. Surimi gel appears to be stabilized against lipid oxidation, as demonstrated by low PV and TBARS levels, when produced with T4. Because of the low level of TBARS, all 10 panelists rated rancid odor as low (~1 out of 4), with no significant variations across treatments. Only treatments with T4 and T6 tended to have a lower fishy odor score as compared to unwashed mince. Scanning electron microscope demonstrated that surimi gels washed with all washing media exhibited microstructures that were very comparable, with the exception of the T6 treatment, which had big pores and aggregates. Based on the quality features, T4 appeared to be the optimal medium to enhance the gel functionality of mackerel surimi.

Improving the thermal stability of polysulfidic crosslinks by hexamethylene‐1, 6‐bis(thiosulfate) disodium salt as the curing agent of natural rubber

Improving the thermal stability of polysulfidic crosslinks by hexamethylene‐1, <scp>6‐bis</scp>(thiosulfate) disodium salt as the curing agent of natural rubber

Dynamic viscoelastic behavior and interlaminar performance of glass/epoxy composites with binary nano‐fillers at different in‐situ elevated temperature environments

AbstractFor commercial civil applications of laminated composite material, characterizations to forecast the interlaminar shear behavior and viscoelastic response across a wide temperature range are essential. In this study, the interlaminar shear strength (ILSS) of glass/epoxy (GE) composites dispersed with binary nanofillers nanosilica‐multilayer graphene (NS‐MLG) and nanosilica‐nanoclay (NS‐NC) was analyzed at an in‐situ testing temperature of 20, 70, and 110°C. Further, the viscoelastic property of the composites was studied using a dynamic mechanical thermal analyzer (DMTA) in the temperature range of 35–165°C. An increase in the ILSS value of around 9% and 10% was observed at room temperature for GE/MLG‐NS and GE/NC‐NS, respectively, compared to control GE composites. In contrast, the trend was seen to change at higher temperatures. There was a slight decrement in the storage modulus (E′) of GE/MLG‐NS and GE/NC‐NS composites in the glassy region compared to control GE composites. The mean Tg of the GE composite (control) was nearly 107.3°C when the E′ decline onset temperature was taken into account, but after the addition of MLG‐NS, it was 10.1°C below. The mean Tg of GE/NC‐NS was determined to be 106.3°C, and in the glass transition as well as rubbery regions, it was observed to compete with the E′ value of the control GE composites. Fractography was done using micrographs obtained from environmental scanning electron microscope (ESEM). Traces of polymeric material found at the fiber surface certified the improved interfacial adhesion between glass fiber and polymer in the matrix‐modified composite samples.

Dynamic viscoelastic behavior of natural cellulose fibers caused by water and the related swelling phenomenon

Dynamic viscoelastic behavior of natural cellulose fibers caused by water and the related swelling phenomenon

Dynamic mechanical and thermal mechanical analysis of Cyperus malaccensis sedge fiber reinforced GO-incorporated epoxy nanocomposites: a short communication

The sedge fiber extracted from the Cyperus malaccensis (CM) plant has recently been found as a promising reinforcement of polymer composites. Incorporation of 30 vol.% CM sedge fibers improved the impact resistance and tensile elastic modulus of epoxy composites with only slight differences in their thermogravimetric parameters. However, dynamic mechanical viscoelastic behavior is still needed to complete these composites characterization for possible engineering applications. This complementary research work extends the previous study to dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) for GO-incorporated epoxy matrix nanocomposites incorporated with 30 vol.% of CM sedge fibers. In comparison to basic epoxy (control sample) the damping factor (tan δ), as the ratio between DMA loss and storage moduli, is significantly increased from 0.45 to 0.75 for 30 vol.% CM fiber composite. TMA findings disclosed only slight variations in the glass transition temperature (119–124 °C) as well as in the thermal expansion coefficient (168 x 10–6 to 220 x 10–6/°C). These DMA and TMA results confirms the promising CM sedge fiber reinforcing effect on GO-incorporated epoxy nanocomposites and its mechanical/thermal viscoelastic contribution.

Dynamic viscoelastic of Phyllostachys iridescens under different moisture contents and radial positions

Viscoelasticity affects polymer behavior when the polymer undergoes deformation, creep, and plasticity. The viscoelasticity of the bamboo can be influenced by moisture content (MC), density, and radial positions. In this study, the effects of moisture contents (MCs) and radial positions on the dynamic viscoelastic behavior of Phyllostachys iridescens, which is a common furniture bamboo species, were investigated using dynamic thermomechanical analysis. The result showed that MC significantly affected on storage modulus, loss modulus, tan δ, and three kinds of glass transition temperatures which were denoted as Tg-E’, Tg-E’’, and Tg-loss respectively, compared with the radial position. With increasing MC, the storage modulus and Tg-loss decreased. Storage modulus decreased from 10,549 MPa at MC 0% to 1896 MPa at MC 80% when 50 ℃, Tg-loss decreased from 233 ℃ at MC 0% to 153 ℃ at MC 7%, 131 ℃ at MC 30%, and 99 ℃ at MC 80% respectively, which showed the increase of MC effectively decreased Tg-loss. As the bamboo wall position changed from yellow layer to middle and green layers, the storage modulus, tan δ, and loss modulus increased, while radial position affected little on Tg-loss. For all MCs and positions, Tg-E’ was higher than Tg-E′’, and the gap between Tg-E′ and Tg-E′’ decreased as MC increased. Tan δ mainly ranged from 0.03 to 0.09 for all MCs and radial positions, and the tan δ at MC 7% was the lowest. Radial positions affected tan δ, which in order of middle layer (0.085) ＞ green layer (0.074) ＞yellow layer (0.059). It showed two peaks on tan δ curve for the green layer, and the later one was 0.663 at 178 ℃, which indicating that green layer shifted to viscous state.

Swelling and Viscoelastic Properties of Cellulose-Based Hydrogels Prepared by Free Radical Polymerization of Dimethylaminoethyl Methacrylate in Cellulose Solution.

The grafting of a stimuli-responsive polymer (poly(dimethylaminoethyl methacrylate)) onto cellulose was achieved by performing free radical polymerization of a vinyl/divinyl monomer in cellulose solution. The grafting and crosslinking efficiency in the material have been increased by subsequent irradiation of the samples with ionizing radiation (doses of 10, 30, or 100 kGy). The relative amount of poly(dimethylaminoethyl methacrylate) in the prepared hydrogels was determined by infrared spectroscopy. The swelling behavior of the hydrogels was studied thoroughly, including microgelation extent, equilibrium swelling, and reswelling degree, as well as the dependence on the gelation procedure. The dynamic viscoelastic behavior of prepared hydrogels was also studied. The tan δ values indicate a solid-like behavior while the obtained hydrogels have a complex modulus in the range of 14-39 kPa, which is suitable for hydrogels used in biomedical applications. In addition, the incorporation of Ag particles and the adsorption of Fe3+ ions were tested to evaluate the additional functionalities of the prepared hydrogels. It was found that the introduction of PDMAEMA to the hydrogels enhanced their ability to synthesize Ag particles and absorb Fe3+ ions, providing a platform for the potential preparation of hydrogels for the treatment of wounds.

Chemical Composition and Rheological Properties of Seed Mucilages of Various Yellow- and Brown-Seeded Flax (Linum usitatissimum L.) Cultivars.

When seeds sown in the soil become wet, their hulls secrete viscous matter that can retain water and thus support germination. Flaxseed mucilage (FSM) is an example of such a material and is attractive for food, cosmetic, and pharmaceutical applications due to its suitable rheological properties. FSM consists mainly of two polysaccharides, namely, arabinoxylan and rhamnogalacturonan I, and it also contains some proteins, minerals, and phenolic compounds. The genotype and the year of the flax harvest can significantly affect the composition and functional properties of FSM. In this work, FSM samples were isolated from flax seeds of different cultivars and harvest years, and their structural and rheological properties were compared using statistical methods. The samples showed significant variability in composition and rheological properties depending on the cultivar and storage time. It was found that the ratio of two polysaccharide fractions and the contribution of less-prevalent proteins are important factors determining the rheological parameters of FSM, characterizing the shear-thinning, thixotropic, and dynamic viscoelastic behavior of this material in aqueous solutions. The yield strength and the hysteresis loop were found to be associated with the contribution of the pectin fraction, which included homogalacturonan and rhamnogalacturonan I. In contrast, the shear-thinning and especially the dynamic viscoelastic properties depended on the arabinoxylan content. Proteins also affected the viscoelastic properties and maintained the elastic component of FSM in the solution. The above structural and rheological characteristics should be taken into account when considering effective applications for this material.

Effect of de-sizing on the structural and mechanical properties of carbon fiber reinforced polypropylene composites molded by the novel direct fiber feeding injection molding technology

Carbon fiber reinforced thermoplastic composites are rapidly emerging as alternative materials for auto parts due to recyclability, excellent stiffness, and strength to weight ratio. In the present study, the influence of carbon fiber de-sizing on the structural and mechanical properties of the sized and de-sized Carbon Fiber Reinforced Polypropylene (CFPP) composites molded by the recently developed novel Direct Fiber Feeding Injection Molding technology was studied. The effect of carbon fiber de-sizing on the structural properties was studied from the fiber dispersion status, fiber orientation factor, fiber volume fraction, and the fiber length. The surface morphology of the sized and de-sized carbon fibers was studied from the Scanning Electron Microscopy (SEM) and Atomic Force Microscope images. The static mechanical properties were studied based on the tensile tests at different loading rate and temperature. The Dynamic Mechanical Analysis tests were conducted to analyze the dynamic viscoelastic behavior of the sized and de-sized CFPP composites. The SEM images were used to observe the failure mechanism. The preliminary results indicated that de-sized composites had better fiber dispersion as compared to the sized CFPP composites. It was found that de-sizing the carbon fiber surface does not significantly affect the carbon fiber length, fiber volume fraction, and fiber orientation in the CFPP composites. Also, the de-sized composites showed better static and thermodynamic mechanical properties caused by the enhanced fiber matrix interaction in CFPP composites as compared to the sized CFPP composites. [Formula: see text]

Preparation, Structural Features and in vitro Immunostimulatory Activity of a Glucomannan From Fresh Dendrobium catenatum Stems.

Dendrobium catenatum polysaccharides (DCPs) have attracted attention due to their multiple physiological activities and health benefits. In this study, a novel water-soluble DCP was obtained from fresh D. catenatum stems through three-phase partitioning and ethanol precipitation at room temperature. Its structural characteristics, rheological property, and in vitro immunostimulatory activity were evaluated. Results demonstrated that DCP was a homogenous polysaccharide with a carbohydrate content of 92.75% and a weight-average molecular weight of 2.21 × 105 Da. This polysaccharide is an O-acetylated glucomannan comprised by glucose, mannose, and galacturonic acid in a molar ratio of 30.2:69.5:0.3 and mainly comprises (1→4)-β-D-mannopyranosyl (Manp), 2-O-acetyl-(1→4)-β-D-Manp, (1→6)-α-D-glucopyranosyl (Glcp), and (1→4)-α-D-Glcp residues. DCP exhibits an extended rigid chain in an aqueous solution and favorable steady shear fluid and dynamic viscoelastic behaviors. In vitro immunostimulating assays indicated that DCP activates RAW264.7 cells, thus markedly promoting macrophage proliferation and phagocytosis and increasing the levels of nitric oxide, interferon-γ, interleukin-6, and interleukin-1β. Moreover, the presence of O-acetyl group and high Mw in DCP might be responsible for its potent immunostimulatory activity in vitro. Therefore, our data suggested that DCP could be developed as a promising immunostimulant in functional food and pharmaceutical industries.

Linear and Nonlinear Viscoelasticity of Polypropylene Containing Cross‐Linked Gels

AbstractThe dynamic viscoelastic and elongational flow behaviors of polypropylene (PP) with increased loading of micron‐sized gelled particles have been investigated. The results reveal that incorporating gel particles can significantly enhance the PP melt storage and loss modulus, complex viscosity, and degree of strain hardening. The gel particle, acting as a soft, deformable filler, exhibits a core–corona structure. The core is made of cross‐linked PP, with the corona region consisting of chain loops, dangling chains, and strongly constrained PP matrix chains. The matrix chains bridge globally between the adjacent gel particles once the interparticle distance is shorter than the PP random coil size. This, in turn, results in a gel‐like behavior of the entire PP matrix. The present findings serve to advance fundamental understanding on the rheological behavior of polymeric systems containing self‐similar soft particles for improving melt strength.

Linear and nonlinear viscoelasticity of self-associative hydrogen-bonded polymers

We conducted a nonequilibrium dissipative particle dynamics simulation on the linear and nonlinear viscoelastic behaviors of polymer melt associated with hydrogen bonds. The effects of the number of hydrogen bonding groups and the strength of hydrogen bonding on viscoelasticity were examined. The simulation results show that the polymers with strongly associating hydrogen bonds exhibit supramolecular networks, and their motion displays some similarities to that of polymer melts following the Reptation model. The strain hardening is due to the strain-induced stretching of polymer chains in the supramolecular networks. The number and lifetime of hydrogen bonding have a combined impact on the dynamic and linear viscoelastic behaviors of self-associative polymers. The storage moduli increase linearly with increasing the numbers of hydrogen bonding groups as the lifetime of hydrogen bonds is comparable to or larger than the relaxation time of polymer chains. In contrast, hydrogen bonding has a less pronounced influence on the dynamics and viscoelasticity as the lifetime of hydrogen bonds is minimal. The results are closely aligned with the experimental findings and provide a deep insight into the viscoelasticity of self-associative polymers via hydrogen bonds.

Dynamic viscoelastic behaviour, gelling properties of myofibrillar proteins and histological changes in shrimp (L. vannamei) muscles during ice storage

Changes in protein quality during ice storage affects the muscle structure, the textural quality, functional properties and the eating quality. Dynamic viscoelastic behaviour and gelling properties ofmeat proteinsin relation to histological changes in white leg shrimp muscles were assessed for 14 days in ice storage. Reduction in Ca2+ ATPase activity of fresh myofibrillar protein (MFP), fading of myosin banding pattern and increased gapping in myofibrils were clearly observed with progress of storage. The quality indices of the shrimp muscle were well correlated with histological and functional properties as a function of ice storage. Solubility of fresh MFP was 86.76% which decreased to 77.06% on the 14th day of storage period. Emulsion capacity found to increase during storage period. Gel strength of white leg shrimp meat was low (81 ± 14 g cm) and further, reduced nearly 60% compared to fresh sample at the end of storage. The considerable reductions (from 535.77 kPa to 246.56 kPa) in storage modulus values were evident of diminishing elasticity and gelling ability of the meat due to ice storage.Therefore, this study usherd that the histological deterioration in myofibrils may be used as an indication of diminishing biochemical quality and gelling behaviour of the proteins.

Onset of Entanglement in Aqueous Solutions of Pullulan with Narrow Molar Mass Distributions

Dynamic viscoelastic behaviors were examined for aqueous solutions of pullulan samples, which are natural polysaccharides with weight-average molar masses (Mw) of 220, 390, and 820 kg mol–1 and narrow molar mass distributions such as Mw/Mn ≤ 1.1, over a concentration range from 5.0 to 467 g L–1 and a temperature range from 1 to 30 °C. The obtained viscoelastic data at different temperatures were superposed to compose master curves for storage and loss moduli (G′ and G″) using the time–temperature superposition principle. The Arrhenius-type temperature dependencies of the shift factors necessary to compose G′ and G″ master curves provided the activation energies (Ev*) of the viscoelastic relaxation times as functions of the concentrations (c) for each pullulan sample. Fundamental viscoelastic parameters such as the average relaxation time (τw), the steady-state compliance (Je), and the zero-shear viscosity (η0) were determined as functions of c for each pullulan sample. Above the critical concentrations (cen ∝ Mw–1) demonstrating the onset of entanglement formation among pullulan molecules, the characteristic relationships, Je–1 ∝ c2, τw ∝ cα–2Mw3.5, and η0 ∝ cαMw3.5 with α = 6.0, were obtained. Although this α value was substantially greater than that for usual synthetic polymers like poly(styrene) dissolved in good solvents where α ∼ 4.5, the Mw exponent of 3.5 for τw and η0 was identical to that of synthetic polymers. The Ev* value was close to the activation energy of the solvent, water viscosity of 19 kJ mol–1, in the dilute regime and abruptly increased with increasing c. Finally, Ev* approached a constant value of ca. 39 kJ mol–1 corresponding to the activation energy necessary for pullulan molecules to release entanglements above cen irrespective of the Mw values. The observed characteristic viscoelastic behaviors of aqueous pullulan solutions are reasonably interpreted by a theoretical model for associating polymers dissolved in good solvents.

Adsorption kinetics and dilatational rheological properties of recombinant Pea Albumin-2 at the oil-water interface

To investigate the adsorption kinetics and dilatational rheological properties of Pea Albumin-2 (PA-2) at the oil-water interface, recombinant PA-2 was expressed and purified. Our native-PAGE, SDS-PAGE, and homology modeling results indicated that PA-2, a kind of globular protein, could form dimers by non-covalent interactions rather than disulfide bonds. The TEM results showed that some PA-2 proteins could form aggregates with the size of around 2–3 μm. Unlike other globular proteins, PA-2 exhibited the non-monotonic kinetic dependency of the dynamic viscoelastic modulus (E). Besides, the rate of rearrangement (kR) of PA-2 was significantly higher than that of other typical food proteins. Our results demonstrated that PA-2 could adsorb to the oil-water interface in the form of aggregates. The addition of 2-ME (β-mercaptoethanol) would impact dilatational rheological properties of PA-2, leading to disaggregation and higher rearrangement of PA-2 protein aggregates at the oil-water interface. Our data offered more information on the interfacial dynamic properties of globular proteins, and provided a new insight to the conformational changes of globular proteins at the oil-water interface, basing on their dynamic viscoelastic behaviors.

Mathematical modelling of Love waves propagation in viscoelastic waveguide loaded with complex fluids

Love waves propagation in a viscoelastic waveguide loaded on its surface with viscoelastic fluids of finite thickness is investigated in this paper. The Maxwell and Kelvin-Voigt constitutive equations are employed in order to describe the fluid viscoelasticity. By solving the equations of motion in the different media (viscoelastic fluid, viscoelastic waveguide and elastic substrate) and imposing the suitable boundary conditions, an accurate and simple generalized complex dispersion equation is established for Love waves. Subsequently, a comparison is made with the published complex dispersion equations in the literature in some particular cases, and a very good agreement is showed. A detailed study was conducted by varying key parameters such as operating frequency, waveguide thickness and fluid thickness. The waveguide surface was subjected to various glycerol concentrations, with a wide range of dynamic viscosity, representing both Newtonian and viscoelastic behaviors. Theoretical analysis shows that to reasonably predict the characteristics responses of Love waves, the Maxwell fluid is more appropriate for low glycerol concentration and, the Kelvin-Voigt fluid is more suitable for high glycerol concentration and at high frequency. Results also evaluated the influence of layer thickness on the dispersion curves. The obtained results can be very useful in the design and optimization of Love wave fluid sensors.

Studies of rheological, electrical, and optical properties of silk fibroin/Benzalkonium chloride modified MMT clay nanocomposite films

This paper highlights about the effect of modification of montmorillonite (MMT) clay with Benzalkonium chloride (BAC) on silk fibroin solution and film properties. MMT was modified by cation exchange method using BAC as the cation. BAC modified nanoclay was incorporated in silk fibroin by ultrasonication method for complete dispersive solution to form nanocomposite solution and films. Uniform dispersion of modified nanoclay in silk fibroin films was observed by FESEM-EDX analysis. Rheological studies of pure silk fibroin and nanocomposite solution showed that on adding the modified nanoclay, viscosity of silk fibroin solution decreases however, at higher loading concentration viscosity changes drastically. Dynamic viscoelasticity behavior analysis of nanocomposites showed a decrease in storage and loss modulus on comparison to pure silk fibroin solution. On adding the nanoclay, an increase in the loss factor was observed with an increase in frequency which indicates the dominancy of viscous behavior in nanocomposite solution. Addition of nanoclay in silk fibroin shows a prominent shift in heat flow observed in DSC analysis. Nanoclay induced the opacity in the nanocomposite films as pure silk fibroin films were more transparent. The electrical properties of nanocomposite films observed that at higher concentration of modified nanoclay showed a dynamic increase in the conductivity.