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In this research, a mixture of three agriculture waste fibres, for the first time, was used as biomodifier after alkali treatment, for enhancing the performance of asphalt binder as 3, 5, 7, and 10 wt%. The physical properties of the novel biomodified binder including penetration, softening point and penetration index were studied. The viscoelastic behavior was investigated by studying flow properties at different shear rates using rotational viscometer. Also, the mechanical characteristics of biomodified asphalt binder were studied using DMA through a series of three types of sweep tests conducted on virgin and biomodified asphalt samples to study the effects of time, temperature and frequency on binder performance. It is observed that the biomodified asphalt binder exhibits the same thixotropic hardening over time with high grade temperature and high rutting resistance. Fatigue parameter (loss modulus) obtained from DMA data was employed to estimate the fatigue resistance of biomodified binder. The results declared that loss modulus of samples were decreased, which proved that the fatigue property was enhanced with biomodifier addition. The biomodifier supports asphalt binder with better properties, and can be applied as a partial replacement for the non-renewable asphalt binders used in the construction of road infrastructure. [ABSTRACT FROM AUTHOR]

Al/SiC functionally graded and metal-matrix composites were investigated through dynamic mechanical analyzer as a function of vibrating frequencies. It was found that internal frictions were strongly dependent on material type and vibrating frequency. Tan δ reached 30.4 × 10–3 and 21.2 × 10–3in FGM and MMC, respectively, at vibrating frequency of 1 Hz. The damping capacity decreased as the frequency increased to 10 Hz and 30 Hz. Storage moduli were 172 GPa and 144 GPa for FGMs and MMCs, respectively, at 1 Hz. Similar to Tan δ, storage moduli of the both materials were more sensitive to frequency change at higher temperatures. In general, higher storage moduli and damping capacities were observed in FGMs compared to MMCs. [ABSTRACT FROM AUTHOR]

The control of silicone rubber's viscoelastic properties such as loss factor, storage and loss moduli at crosslinking stage is crucial in their malleability. Hence, the objective in this study is to investigate the rheological behaviour of silicone rubber cured under different formulation using platinum catalysts and triethylamine, methanol & ethanolamine solvents. Measurements were conducted for the silicone rubber to cross-linker ratios of 2.5:7.5, 5:5, 7.5:2.5 and 10:1 at different temperatures, as well as for the silicone rubber with triethylamine, methanol and ethanolamine at different angular frequencies. The crossover of storage and modulus curve which signifies a gel point was not observed at higher ratios of platinum used across the temperature range of25 - 100°C. However, the crossover was observed at 89 and 95°C with the formulation ratios of 10:1 and 7.5:2.5, respectively. On the other hand, the crossover point was observed for silicone rubber at 100 s-1 for triethylamine, 3 s-1 and 100 s-1 for methanol, and 70 s-1 alongside 290 s-1 for ethanolamine. The presence of gel point indicates that crosslinking of silicone rubber and this study proves the possibility of controlling the crosslinking behaviour.. [ABSTRACT FROM AUTHOR]

The influence of thermal processing and mechanical alloying of powder particles on the dynamic behavior and microstructural changes occurring in an Fel4Mn6Si9Cr5Ni (mass%) alloy is investigated. Five batches of 66Fe-14Mn-6Si-9Cr-5Ni (mass%) powder mixtures were produced via powder metallurgy. After powder mixing, different volume fractions (from 0 to 40 vol%) were mechanically alloyed, remixed with the rest of as-blended particles, compressed, sintered and subsequently hot rolled to a thickness of 1 mm. They were then subjected to a thermal treatment (annealing) at different temperatures and subsequently quenched into water. Thus, we had 25 different specimens for experimentation. The specimens were then machined and loaded in tension and subjected to dynamic mechanical analysis (DMA) by varying the temperature and strain amplitude. In the DMA tests, the samples were cycled between the ambient temperature and 673 K keeping the amplitude constant, while varying the temperature. These results were then correlated to the thermomagnetic properties that were measured in the same range of temperatures. Based on these data, the internal friction (tan δ) maxima, correlated with storage modulus (E′) discontinuities, were associated with the multistage reverse transformations of martensite (ε, hcp) to austenite, superimposed over the antiferromagnetic–paramagnetic transitions and accompanied by magnetization peaks (Neel temperature). The temperature ranges pertaining to tan δ maxima, E′ discontinuities and magnetization peaks were determined and discussed in terms of thermal processing temperature and volume fraction of mechanically alloyed powder particles. The variation of storage modulus with strain for three different cycles (with strain amplitude varying from zero to maximum) was traced for three different temperatures: (i) T = RT; (ii) T < Ttanδ (max); (iii) T > Ttanδ (max). The role of magnitude of thermal treatment temperature and volume fraction of mechanically alloyed powder particles on the storage modulus plateaus were given prominence for these temperatures (RT, below tanδmax and above tanδmax) as they influence the evolution of the microstructure. [ABSTRACT FROM AUTHOR]

In the present study, nanosilica reinforced polylactic acid wood composite was fabricated using Fused Filament Fabrication (FFF) 4D printing technology. Nanosilica content was varied to study the effect on shape memory property like shape recovery rate and mechanical properties such as hardness, compressive strength and dynamic mechanical properties and simultaneous thermal properties. The finding of result indicated that the mechanical properties such as hardness, compressive strength, and flexural strength were increased by 60%, 60%, and 16.6% with the addition of 2 wt% nanosilica. The thermal stability of composite was also improved with the addition of nanosilica. The storage modulus was initially increased and then decreased with the increase in nanosilica content. However, the maximum shape recovery rate was decreased with the increase in nanosilica content. [ABSTRACT FROM AUTHOR]

Reinforcement of epoxy glass fabric composites with nano‐ and micro‐fillers has resulted in the development of polymer composites with good electrical, thermal, and mechanical properties. The present work attempts to estimate the impact of hybrid fillers on dynamic‐mechanical properties of the epoxy composites with a different filler. The dynamic mechanical parameters such as storage modulus, loss modulus, and damping factor over a temperature of 25°C–250°C have been investigated. The viscoelastic properties of composites are also confirmed with a Cole‐Cole plot. From the results, the storage modulus of the composites is observed to lie in the range of 8000 to 12,500 MPa, and the epoxy composite with silicon carbide filler shows the highest storage modulus. Composite with 5 wt% of alumina shows the maximum loss modulus of 2100 MPa. The glass transition temperature of the base epoxy composite is 135°C and it increases to 137°C with the incorporation of hybrid cenosphere and molybdenum sulfide fillers. The storage modulus shows only marginal differences as compared to their counterparts with nanofillers but is higher by about 10–15% in comparison to the micron filler‐based composites. However, the differences in the loss modulus of the nanocomposites, hybrid composites, and the composites with micron‐sized filler are not significant. [ABSTRACT FROM AUTHOR]

A model is presented to predict the linear viscoelastic rheology of hydrophobically modified adhesive soft particle glasses in an aqueous solution. The hydrophobes on the surfaces of particles in contact preferentially associate with each other, creating an adhesive force between particles. The extent of this adhesive force depends on the number of associating or physically bonded hydrophobes and the strain on the bonds. The model is first presented for two horizontal surfaces with hydrophobes attached to them. The force required for oscillatory movement between these adhesive surfaces exhibits a Maxwellian behavior with a single relaxation time that is about the time for hydrophobe dissociation. The model is extended to predict the storage and loss moduli of adhesive soft particle glasses in ordered cubic lattices. In addition to the adhesive force, the particles also exhibit repulsive elastic and elastohydrodynamic interparticle forces. For situations where there is no adhesive force between particles, the storage modulus is independent of frequency, and the loss modulus is a linear function of frequency. The storage and loss moduli as functions of frequency are richer with adhesive forces. The storage modulus exhibits two plateaus, one at low and one at high frequency. The loss modulus exhibits a local maximum in frequency that occurs at approximately the dissociation rate of the hydrophobes. [ABSTRACT FROM AUTHOR]

The intramolecular relaxation dynamics of unconcatenated ring polymers in dilute solutions is theoretically investigated within the framework of the Rouse–Zimm theory. The excluded volume interactions (EVIs) between the nonbonded monomers are modeled by a harmonic potential, where the interaction parameter is evaluated from Flory's mean-field approach. The hydrodynamic interactions (HIs) between the pairs of monomers are approximated by a preaveraged Oseen tensor. The mechanical moduli are dominated by the smaller relaxation rates corresponding to the collective relaxation modes in the low frequency regime, while they are governed by the higher relaxation rates corresponding to the local relaxation modes in the high frequency regime. EVI decreases the relaxation rates of the normal modes where the decrease for the collective modes is larger than that for the local modes, which consequently expands the width of the relaxation spectrum. The characteristic overall relaxation time is evaluated from the inverse of the crossover frequency, which is the same for rings of various sizes with HI and with both HI and EVI, while it shifts to lower frequencies with increasing ring size for the Rouse rings. [ABSTRACT FROM AUTHOR]

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The primary goal of this study is to highlight the rheological and mechanical properties of a new blend composed of naturally-derived hydrogel materials- psyllium husk (PH) and gelatin (G) for its potential use in three-dimensional (3D) printing technology. The mixtures were prepared at various weight ratios of 100PH, 75PH + 25G and 50PH + 50G. A suitable selection of the printable ink was made based on the preliminary screening steps of manual filament drop test and layer stacking by 3D printing. Printing of the common features such as hexagon and square grids helped evaluating shape fidelity of the chosen ink. Although 50PH + 50G blend was found meeting most of the criteria for an ideal 3D printable ink, rheological and mechanical characterizations have been performed for all the ratios of polymeric blends. This study documents the correlation between various factors of rheology that should be taken into account while categorizing any biomaterial as a printable ink. Yield stress was measured as 18.59 ± 4.21 Pa, 268.74 ± 13.56 Pa and 109.16 ± 9.85 Pa for 50PH + 50G, 75PH + 25G and 100PH, respectively. Similarly, consistency index (K) and flow index (n) were calculated using the power law equation and found as 49.303 ± 4.17, 530.59 ± 10.92, 291.82 ± 10.53 and 0.275 ± 0.04, 0.05 ± 0.005, 0.284 ± 0.04 for 50PH + 50G, 75PH + 25G and 100PH, respectively. The loss modulus (G″) was observed dominating over storage modulus (G′) for 50PH + 50G, that depicts its liquid-like property; whereas storage modulus (G′) was found dominating in case of 75PH + 25G and 100PH, indicating their solid-like characteristics. In addition, the loss tangent value (tan δ) of 50PH + 50G was observed exceeding unity (1.05), supporting its plastic behavior, unlike 75PH + 25G (0.5) and 100PH (0.33) whose loss tangent values were estimated less than unity revealing their elastic behavior. Also, 50PH + 50G was found to have the highest mechanical strength amongst the three blends with a Young's modulus of 9.170 ± 0.0881 kPa. [ABSTRACT FROM AUTHOR]

Natural cellulosic fibres, such as kenaf, have potential for use as replacement of man-made fibres in polymeric composites. The rapid depletion of synthetic resources, such as petroleum, and the growing consciousness of global environmental problems related to synthetic products push toward the acceptance of natural fibres as biocomposite components. Kenaf (Hibiscus cannabinus L.) is a multipurpose hibiscus species used to make engineered wood, clothing, packing material, rope and twine. Kenaf is essentially made up of cellulose (about 70%), predicting its excellent mechanical performance. Kenaf fibres are chemically treated before mixing with other polymer resins to enhance their fibre properties. Based on the previous literature, the effect of chemical treatment on the dynamic mechanical performance of kenaf cellulosic biocomposites remains unexplored. The present review focuses on the recent works on the influence of major chemical treatments used on kenaf fibre, such as alkaline, silane and acetylation on fabricated biocomposites. The present review also unveils other chemical treatments (e.g. zein and amino acid) and combined treatments on the fibre to improve the biocomposites' dynamic mechanical behaviour. [ABSTRACT FROM AUTHOR]

Damping is largely increasing with the vibration amplitude during nonlinear vibrations of rectangular plates. At the same time, soft materials present an increase in their stiffness with the vibration frequency. These two phenomena appear together and are both explained in the framework of the viscoelasticity. While the literature on nonlinear vibrations of plates is very large, these aspects are rarely touched. The present study applies the fractional linear solid model to describe the viscoelastic material behavior. This allows to capture at the same time (i) the increase in the storage modulus with the vibration frequency and (ii) the frequency-dependent nonlinear damping in nonlinear vibrations of rectangular plates. The solution to the nonlinear vibration problems is obtained through Lagrange equations by deriving the potential energy of the plate and the dissipated energy, both geometrically nonlinear and frequency dependent. The model is then applied to a silicone rubber rectangular plate tested experimentally. The plate was glued to a metal frame and harmonically excited by stepped sine testing at different force levels, and the vibration response was measured by a laser Doppler vibrometer. The comparison of numerical and experimental results was very satisfactorily carried out for: (i) nonlinear vibration responses in the frequency and time domain at different excitation levels, (ii) dissipated energy versus excitation frequency and excitation force, (iii) storage energy and (iv) loss factor, which is particularly interesting to evaluate the plate dissipation versus frequency at different excitation levels. Finally, the linear and nonlinear damping terms are compared. [ABSTRACT FROM AUTHOR]

This paper calls attention to important issues that have not been considered regarding linear amplitude sweep (LAS) test in previous publications: Is the relationship between the storage modulus logarithm [ logG′(ω) ] and frequency logarithm [ log(ω) ] linear in the whole range of experimental frequencies? If not, what is the influence on the fatigue life of asphalt binders calculated using the AASHTO protocol? In which range of frequencies is the relation between the storage modulus logarithm [ logG′(ω) ] and frequency logarithm [ log(ω) ] linear in the whole range of experimental frequencies? Does fatigue life follow a normal distribution? Several tests were conducted using three different types of asphalt binder [neat, crumb rubber–modified (CRM), and styrene–butadiene–styrene (SBS)–modified asphalt]. Residual analysis showed a lack of fit, indicating the inadequacy of the linear model in the whole range of experimental frequencies. This inadequacy may suggest that the protocol produces an overestimation of the binder fatigue life. In addition, a sequential search reveals that the relationship between logG′(ω) and log(ω) is linear in a limited subset of frequencies. The empirical distribution of the fatigue life is built by an extensive Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Hydrogels have been extensively studied for biomedical applications such as drug delivery, tissue-engineered scaffolds, and biosensors. There is a gap in the literature pertaining to the mechanical properties of hydrogel materials subjected to high-strain dynamic-loading conditions even though empirical data of this type are needed to advance the design of innovative biomedical designs and inform numerical models. For this work, HEMA-DMAEMA hydrogels are fabricated using a photopolymerization approach. Hydrogels are subjected to high-compression oscillatory dynamic mechanical loading at strain rates equal to 50%, 60%, and 70%, and storage and loss moduli are observed over time, e.g., 72 h and 5, 10, and 15 days. As expected, the increased strains resulted in lower storage and loss moduli, which could be attributed to a breakdown in the hydrogel network attributed to several mechanisms, e.g., increased network disruption, chain scission or slippage, and partial plastic deformation. This study helps to advance our understanding of hydrogels subjected to high strain rates to understand their viscoelastic behavior, i.e., strain rate sensitivity, energy dissipation mechanisms, and deformation kinetics, which are needed for the accurate modeling and prediction of hydrogel behavior in real-world applications.

In this article, a magnetorheological shear thickening fluid (MRSTF) was fabricated based on magnetorheological (MR) material and shear thickening fluid (STF). The STF was firstly fabricated as the liquid phase, and carbonyl iron particles were then mixed with the prefabricated STF to synthesise a series of MRSTFs with various iron concentrations. Then, a rheometer was used to measure their viscosities by varying the shear rate under various magnetic fields. Both static and dynamic tests were conducted to study the rheology of MRSTFs under different magnetic fields. The tested results revealed that the MRSTF showed shear thickening under zero magnetic field and MR effect with increasing applied magnetic field. It was also noted that the viscosity of the MRSTFs can be controlled by both shear rate and the applied magnetic field. The concentration of iron particles played an important role in the MRSTFs’ rheological properties. The MRSTFs with higher iron particle concentrations revealed lower shear thickening effects but higher MR effects, which means the MRSTF with higher iron concentration can be treated as an effective MR fluid. Meanwhile, the MRSTF with low iron concentration displays good shear thickening effect under weak magnetic field. To summarise the behavior of MRSTFs with various iron concentrations and under different magnetic fields, three regions were proposed to provide guidelines to design MRSTFs and assist in their applications.

This article provides comprehensive experimental data of two water-swelling materials, water swelling rubber (WSR) and water-swelling polyurethane (WSP). Swelling tests, Dynamic Mechanical Analyzer (DMA) and Scanning Electron Microscope (SEM) were performed. Sealing properties of WSR and WSP were characterized by the data of swelling ratios (Sw and Sa), storage moduli (E') and images of micro-damage morphologies. These data can be useful for the prediction of the long-term waterproof performance of water-swelling materials and provide reference for material selection. The data presented herein was used for the article, titled “Laboratory evaluation of long-term sealing behaviors of two water-swelling materials for shield tunnel gasket” [1].

Magnetorheological elastomer (MRE) consists of magnetic particles known as carbonyl iron (CIPs), which have been locked in a silicone-based matrix, in various alignments. However, current MRE exhibits inadequate rheological properties due to several issues such as particle alignments. Therefore, in this study, a new approach of the particle alignment of CIPs in MRE, namely fountain-like structure, is introduced. It is expected that this kind of MRE exhibits enhancement rheological responses, in off- and on-state conditions. This work includes the development of a new mold that can produce various directions of magnetic flux lines in order to have fountain-like structures of CIPs in MRE, during the curing process. Three types of particle alignments in MRE, namely isotropic, fountain-like and inverted fountain-like, are fabricated. The rheological properties of MRE in terms of storage modulus and MR effect are measured in an oscillatory shear mode using a rheometer. The results have revealed that fountain-like MRE exhibits higher storage modulus than the isotropic MRE, approximately 0.6 MPa of increment in the strain sweep test, in an on-state condition. Furthermore, it has been demonstrated from strain, frequency and the current sweep test that the rheological properties of fountain-like MRE related to storage modulus and magnetorheological (MR) effect are higher compared to the inverted fountain-like MRE.

In the present study, the effects of magnesia particles on thermal, dynamic mechanical, morphological, and surface properties of polystyrene resin are investigated. In general, the addition of magnesia particles in polystyrene matrix increases the thermal stability, storage modulus, and wettability, on other hand does not affect the molecular mobility. SEM results showed a limited distribution of magnesia particles in the polystyrene matrix at 15 wt.%.

A carbon fibre/geopolymer composite whose matrix was based on potassium silicate and metakaolin was subjected to different curing temperature modes. The effect of the treatments was evaluated by testing the stiffness and water uptake resistance of the composite. The structure of the composites was analysed by scanning electron microscopy, X-ray diffraction and nuclear magnetic resonance. It was determined that the highest stiffness was achieved by the primary curing at 80 °C. Contrary to this, curing at temperatures higher than 100 °C increased the resistance to water uptake, resulting in smaller decrease in the storage modulus. Structural changes of the geopolymer were linked to the course of the curing temperature mode. Two types of the curing were suggested for the use of the carbon fibre/geopolymer composite in heat stress applications and in a humid environment, respectively.

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Effect of solid fat content (SFC) on the storage modulus (G′) and loss modulus (G″) of margarines was investigated. The G′ and G″ increased linearly with SFC in a double-logarithmic plot, independent of the types of margarine. There was a minor effect of dehydration on the G′ of margarine. Secondly, effect of the margarines on the G′ and yield stress of cookie dough was investigated. They could be corresponded to the G′ of each margarine in a double-logarithmic plot, independent of the types of margarine. These results will be useful to predict the die cutting and kneading properties of cookie dough. Finally, effect of the margarines on the texture properties of cookie was investigated at various temperature and water activity (aw) conditions. It was expected that the cookie samples having aw = 0.328 and aw = 0.753 were glassy state and rubbery state, respectively. Fracture stress of the cookie samples decreased with increasing temperature, and this behavior could be described as a linear relationship between log fracture stress and log G′ of dehydrated margarines. From the result, it was found that the fracture stress increased gradually (glassy cookie) and remarkably (rubbery cookie) with the G′ of dehydrated margarines. The reason why there was a major effect of margarine on the texture of rubbery cookie will be that amorphous hydrophilic part of the cookie was enough soft to be affected by the margarine. [ABSTRACT FROM AUTHOR]

The inflammability of wood fiber/high‐density polyethylene composites (WPCs/HDPE) remains a limitation for its application. Here the authors sought to improve the flame retardancy of WPCs by incorporating uniformly dispersed SiO2. Specifically, micron‐ and nano‐SiO2 were incorporated into HDPE via dry blending (dry dispersion) or solution blending (wet dispersion), to prepare the compounded matrices for the WPCs. The effects of SiO2 size and dispersion mode on the thermal stability and fire retardancy of WPCs were investigated. The results indicated that the nano‐SiO2 was more beneficial to improve the thermal stability of WPCs than the micron‐SiO2, especially incorporating via wet dispersion. The cone calorimetry tests revealed that incorporating 9 wt% micron‐SiO2 slightly decreased the heat release and smoke production of the WPCs. The incorporation of nano‐SiO2 in WPCs showed a moderate reduction in the heat release, while slightly increased the smoke production. The wet dispersion presented minor advantage over dry dispersion in improving the flame retardancy of WPCs. In addition, the dynamic thermal‐mechanical analysis revealed that the WPCs containing wet‐dispersed micron‐ or nano‐SiO2 exhibited a higher storage modulus compared to that dry‐dispersed SiO2. [ABSTRACT FROM AUTHOR]

In order to prepare excellent electro-responsive natural hydrogels, in this paper, soluble starch with large amount of hydroxyl groups was selected as raw material. For exploring the enhancement to electro-response of starch hydrogel, starch-Fe(III) composite hydrogels were successfully obtained by a combination of Fe(III) into starch hydrogel in this paper. The composite hydrogels were prepared as A-hydrogels cured in the presence of electric field and B-hydrogels which cured without electric field. The storage modulus of A-hydrogels and B-hydrogels was measured using a dynamic viscoelasticity spectrometer (DMA); the consequent modulus increment (ΔG = GA-GB) and modulus increment sensitivity (ΔG/GB) were analyzed for indicating electro-response of the hydrogels. The physical microstructure of the hydrogels was observed by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to study the chemical constitution and structure. The results show that there is a coordinate bond between Fe(III) with –OH of starch which leads to a stronger three-dimensional network structure and higher thermal stability of the starch-Fe(III) hydrogel. What's more, the electro-response of the hydrogels can be affected according to the Fe3+ concentration. When the Fe3+ concentration is 0.15 ~ 0.25 M under the electric field of 0.8 kV mm−1, the starch-Fe(III) hydrogels have the strongest electro-response, the maximum value of modulus increment (ΔG) is 24 kPa, and the modulus increment sensitivity (∆G/GB) is about 90%, far more than pure starch hydrogel. [ABSTRACT FROM AUTHOR]

The engagement of waste tires rubber as source of raw materials for different applications can be a partial solution to the great environmental problems caused by these products. In this study, waste tire rubber was devulcanized using both mechano–chemical and microwave methods. This process was achieved using different concentrations of 2-mercapto benzothiazole disulfide (MBTS) and tetramethylthiuram disulfide (TMTD) as a devulcanizing agent and different microwave devulcanizing times. The optimum content of both MBTS, TMTD and suitable microwave treatment time to make continuous film were noted. The devulcanized waste rubber was then added, at different concentrations, to virgin styrene–butadiene rubber (SBR). The thermal properties and dynamic mechanical behaviors were investigated for all blends. The thermal analysis proved that natural and styrene butadiene rubber are the main two constituents of the waste tire rubber utilized in this study. The mechanical behavior of the SBR blends remarkably improved by using 20 phr waste rubber (WR) devulcanized by 2 phr MBTS and by exposure for 2.2 min to microwaves. Storage modulus, tearing strength and tension set behaviors notably improved for all SBR/WR blends by irradiating with gamma ionizing radiation with a dose of 100 kGy and further improvement could be attained by increasing the dose up to 200 kGy. [ABSTRACT FROM AUTHOR]

In general hydrogel synthesis uses a trial and error method when creating new hydrogels and searches afterwards for a fitting application of the received hydrogel. A much more effective and sustainable approach would be to have an application in mind before starting a targeted synthesis of a hydrogel with specific properties. Hence the goal of the study is to investigate influencing factors—crosslink density here represented through the degree of substitution, mass average molecular mass, mixing ratio and time for gelation—to the storage modulus G ′ for covalently cross-linked hydrogels based on oxidized cellulose sulfate and carboxymethyl chitosan. The results can be summarized as follows: higher values for G ′ can be reached by increasing the mass average molecular mass, the crosslink density and by shifting the mixing ratio toward the polymer which determines the number of possible cross-linkings in the hydrogel. The findings of this work may be transferred to similar systems and are helpful for a targeted synthesis of hydrogels with specific characteristics. [ABSTRACT FROM AUTHOR]

The present study focuses on the effect of moisture uptake of jute/epoxy, hemp/epoxy, flax/epoxy and hybrid composites (jute/hemp/epoxy, hemp/flax/epoxy and jute/hemp/flax/epoxy) on the dynamic mechanical and tribological properties. Composite specimens were developed using hand lay-up compression technique. The developed composites were dipped in normal tap water at room temperature for the span of one year. Three parameters were used to analyze the results of dynamic mechanical analysis (damping capability, storage modulus and loss modulus), and three parameters (friction force, coefficient of friction and specific wear rate) were used to analyze the wear test results. Results of dynamic mechanical analysis and wear analysis after one year of moisture absorption were compared with already published results for specimens without moisture absorption. Substantial changes were observed in each parameter of dynamic mechanical analysis and tribology test performed after one year of water immersion. Water-saturated hybrid composite jute/hemp/epoxy achieved highest reduction of 16.03% in damping capability as compared to its dry specimens. Water-immersed jute/epoxy composite achieved highest increment of 763.2% and 589.8% in the value of storage modulus and loss modulus, respectively, as compared to its dry specimen. Hybrid composite jute/hemp/flax/epoxy achieved the highest increment of 13.5% and 19.9% in the value of coefficient of friction as compared to its dry specimen at 3 and 5 m/s sliding speed, respectively. Water-immersed hemp/flax/epoxy achieved the highest increment of 228.9% and 51.56% in the value of specific wear rate at 1 and 3 m/s sliding speed, respectively, as compared to its dry specimen. [ABSTRACT FROM AUTHOR]

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This paper establishes an empirical formula to predict the strain amplitude effect. A viscoelastic constitutive model—the superposition of a hyperelastic model and a viscoelastic model—is constructed based on the laws of thermodynamics. The Mooney–Rivlin model and the Prony series are employed for uniaxial tension testing. The empirical formula is derived using a hysteresis loop; it obtains results that are in agreement with the experimental results of dynamic mechanical analysis (DMA). The empirical formula proposed in this paper has certain accuracy in predicting the dynamic modulus under different strain amplitudes. [ABSTRACT FROM AUTHOR]

We investigate the potential of Brillouin Light Scattering (BLS) Microspectroscopy for fast non-invasive all-optical assessment of the mechanical properties of viscose fibers and bleached softwood pulp. Using an optimized Brillouin spectrometer, we demonstrate fast spatial mapping of the complex longitudinal modulus over extended areas (> 100 µm). Our results reveal that while the softwood pulp has a relatively uniform moduli, the viscous fibers have significant spatial heterogeneous in the moduli. Specifically, the viscose fibers exhibited a regular pattern of increasing and decreasing modulus normal to the fiber axis. The potential influence of a locally changing refractive index is investigated by holographic phase microscopy and ruled out. We discuss our results in light of the anisotropic mechanical properties of the fibers and are able to estimate the relative difference between the modulus along the fiber axis and that perpendicular to it. Results are presented alongside reference measurements of the quasi-static mechanical properties transverse to the fiber axes obtained using AFM-nanoindentation which reveal a similar trend, hinting at the potential usefulness of BLS for mechanical characterization applications. However, more detailed investigations are called for to uncover all the factors influencing the measured high-frequency BLS modulus and its significance in relation to physical properties of the fiber that may be of practical interest. [ABSTRACT FROM AUTHOR]

The random-branched and the star-like branched polystyrenes were prepared by atom transfer radical polymerization (ATRP). Then the random-branched polystyrene and star-like polystyrene were blended with the linear polystyrene. The structure and properties of the polymers were characterized by triple detection size exclusion chromatography (TD-SEC), diffusing wave spectroscopy (DWS), differential scanning calorimetry (DSC) andmechanical property testing. The results showed that the tensile strength of the industrial-grade polystyrene blended with the branched polymer decreased with the amount of branched polystyrene. But it was increased when the high storage modulus of BPS was used by keeping the BPS amount constant. The glass transition temperature of the industrial-grade polystyrene blended with the branched polymer decreased with increased amount of the BPS. For an example, the glass transition temperature of the polystyrene blend dropped by 1.87°C when 5wt% of the BPS was added to the blend. [ABSTRACT FROM AUTHOR]

(100 − x)PVDF–(x) PZT (PVDF: Polyvinylidene Difluoride and PZT: Lead Zirconate Titanate) composite was prepared in 0–3 connectivity by the solvent casting methods. The piezoelectric co-efficient is found to be increased with the increase in PZT concentration in the PVDF matrix. It is due to the increase of β phase of PVDF as well as lattice strain in PZT. The incorporation of PZT ceramics in the PVDF matrix causes an increase in storage loss modulus of the sample. The tanδ decreases due to incorporation of PZT ceramics in the PVDF matrix. The piezoelectric and mechanical properties are found to be increased in the PVDF-PZT composite compare to that of PVDF. [ABSTRACT FROM AUTHOR]

Inulin has been used as a fat substitute in baked goods due to its gelling properties and functionality. However, it usually has been done in low substitution levels. The aim of this study was to evaluate the effect in rheological parameters in cassava dough caused by high substitution levels of fats by inulin. Physical and chemical characterization of biscuits were done for evaluation of dough's potential usage in bakery products. Substitution of mozzarella cheese by inulin showed that up to 12.5 g inulin per 100 g cassava flour led to a lower storage modulus, suggesting bakery potential for bread like products. Higher substitutions (25 g, 37.5 g, and 50 g per 100 g cassava flour) led to a higher storage modulus and suggest a potential for cookies and similar products. Hardness results obtained support rheological ones, suggesting higher substitution levels are suitable for cookies and similar products. This is inferred by observing an increase in hardness ranging from 5.80 N up to 17.47 N. Cassava dough with fat substituted by inulin in high levels, has potential in the development of different baked goods. [ABSTRACT FROM AUTHOR]

In this study, the degradation of tensile properties is investigated by placing the neat ethylene propylene diene monomer (EPDM) rubber and different weight percentages (2 wt%, 4 wt% and 6 wt%) of MMT clay dispersed in the EPDM rubber samples in a humidity chamber for 0, 5, 7, 12 and 14 days. The thermal properties of neat EPDM rubber and its clay nanocomposites were studied by using different instruments, namely dynamic mechanical analyser (DMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The viscoelastic properties are studied over the temperature range of −80°C to 80°C at different frequencies by using DMA. An increase in storage modulus and the decrease in loss tangent values are observed with the increase in clay content from 0 wt% to 6 wt% in EPDM rubber. Increase in storage modulus and glass transition temperature (Tg) values is observed with the increase in frequency from 1 Hz to 50 Hz. Also, the thermal stability and change in mass of these materials as a function of temperature and time are studied using TGA. It is found that EPDM/4 wt% clay composites exhibit the highest residual weight at 690°C while neat EPDM exhibits the highest weight loss compared to samples dispersed with other clay weight percentages. Using X-ray diffraction (XRD), 2θ value was measured and the crystal structure is investigated. Fourier transformed infrared spectroscopy (FTIR) was used to characterise the grafting of clay in the EPDM rubber. The dielectric constant and conductivity were studied for different frequencies and temperatures. [ABSTRACT FROM AUTHOR]

Dough fermentation with lactic acid bacteria has been extensively studied due to the associated health benefits and its effects on physical and rheology parameters in dough and bread. However, most of the studies rely on long fermentation times. The aim of this study is to evaluate the effect of short fermentation times (0 to 8 h) with Lactobacillus paracasei in rheology, physical and chemical properties on cassava dough and biscuits. Both storage modulus and loss modulus decreased as the fermentation times increased, down to 54,206.67 ± 13,348 and 17,453.89 ± 3691 Pa, respectively. Fermentation with L. paracasei influenced biscuit's hardness and chemical properties, and gas cell sizes were increased notably. These results suggest that short fermentation times could be used to improve dough's rheological characteristics. [ABSTRACT FROM AUTHOR]

This study describes an investigation into the physical, mechanical and dynamic mechanical properties of coir (coconut fiber) and coconut husk particulates reinforced polymer composites which were prepared by the hot press method. The impact of coir loading on the physical and mechanical properties of the composites was examined in more detail. It was observed that the values of rigidity, flexural strength and hardness were raised up to 7.1 MN/m2, 17.0 MPa and 92.5 MN/m2, with increase in coir length. Impact energy reduced proportionately with increment in fiber length (from 0.78 J at no fiber inclusions to 0.42 J at 30 mm fiber length). With the increment of fiber length from zero to 10 mm, a reduction in density and increment in water absorption properties was observed. These properties (density and water absorption) remained with increase in fiber length for a given structure of matrix/filler. The surface morphology of composite with longest fiber length (30 mm) was investigated. Fiber pullout and little voids on composite surfaces were seen. Fundamentally, these regions can encourage the matrix impregnation onto the fiber. At the highest fiber loading and at highest frequency (10 Hz) used during the dynamic mechanical examination, the tan δ peak gets widened, underlining the enhanced fiber/matrix grip. Also, extra and noticeable peaks were seen at higher frequency conditions in the tan δ curves, because of the interlayer phenomenon. [ABSTRACT FROM AUTHOR]

Heat dissipation is very essential for the efficient working of electronic devices. There is a widespread demand for high thermal conductivity materials. Boron nitride nanotubes have high thermal conductivity but due to their poor interfacial adhesion with polymers, their use as heat dissipating material is restricted. In this study, a silane-coupling agent has been used to modify the boron nitride nanotubes. These tubes were then inserted in polymethyl methacrylate matrix. Various properties such as thermal conductivity, storage modulus, and loss factor have been predicted. Molecular dynamics simulations have also been used for accurate prediction of the properties of boron nitride nanotubes/polymethyl methacrylate composites. The boron nitride nanotubes weight percentage was varied from 0% to 70% for studying the effect on thermal conductivity, storage modulus, and loss factor. The experimentally obtained thermal conductivity increased rapidly from 0.6 W/mK at 40 wt.% of boron nitride nanotubes to about 3.8 W/mK at 80 wt.% of boron nitride nanotubes in polymethyl methacrylate matrix (an increase of nearly 533%). A similar trend was obtained using molecular dynamics simulations. The storage modulus increased from 2 GPa (for pure polymethyl methacrylate) to about 5 GPa (for 70 wt.% boron nitride nanotubes). The glass transition temperature of boron nitride nanotubes/polymethyl methacrylate composites shifted to higher temperatures with an increase in boron nitride nanotubes weight percentage. [ABSTRACT FROM AUTHOR]

Natural fiber polymer composites are gaining focus as low cost and light weight composite material due to the availability and ecofriendly nature of the natural fiber. Fiber composites are widely used in civil engineering, marine and aerospace industries where dynamic loads and environmental loads persist. Dynamic analysis of these composites under different loading and environmental conditions is essential before their usage. The present study focuses on the dynamic behavior of areca nut husk reinforced epoxy composites under different loading frequencies (5 Hz, 10 Hz and 15 Hz) and different temperatures (ranging from 28°C to 120°C). The effect of loading and temperature on storage modulus, loss modulus and glass transition temperature was analyzed. Increase in storage modulus is observed with increase in loading frequency. The storage modulus decreases with increase in temperature. The glass transition temperature of the composite is determined to be 105°C. The elastic modulus calculated from the DMA data is compared with three point bending test. [ABSTRACT FROM AUTHOR]

A special class of smart material was developed using shape memory polyurethane (SMPU) elastomer and graphene nanoplatelets (GNPs) via melt-blending process using micro-compounder. The shape recovery of the developed composites was studied under microwave irradiation. The nanocomposites were developed having 0.2, 0.4, 0.6, and 0.8 phr GNPs in the SMPU matrix. The effects of GNP reinforcement on morphology, shape memory effects, and viscoelastic properties of the composites were investigated. The recovery stress of virgin SMPU increased with reinforcement and maximized on the incorporation of 0.6 phr GNPs. The deformation-induced shape memory creation process influenced significantly the recovery stress of composites as compared to virgin SMPU. The recovery stresses of SMPU at 50, 75, and 100% strain were 1.5, 1.7, and 1.9 MPa, whereas the values of GNP-SMPU composites were 3.2, 3.4, and 4.1 MPa corresponding to 0.6 phr GNP reinforcement. The value of storage modulus above the glass transition temperature of SMPU increased from 9.2 to 15.1 MPa on the addition of 0.6 phr GNPs. The peak of the damping factor, tan δ shifted toward higher temperatures with the increased GNP content. The morphological study confirms the uniform dispersion of GNPs in the SMPU matrix. The microwave-induced heating of 0.8 phr GNP composite shows 80% shape recovery in 60 s, which is faster than convectional heating. [ABSTRACT FROM AUTHOR]

BACKGROUND: Laminopathies are genetic diseases caused by mutations in the nuclear lamina. OBJECTIVE: Given the clinical impact of laminopathies, understanding mechanical properties of cells bearing lamin mutations will lead to advancement in the treatment of heart failure. METHODS: Atomic force microscopy (AFM) was used to analyze the viscoelastic behavior of neonatal rat ventricular myocyte cells expressing three human lamin A/C gene (LMNA) mutations. RESULTS: Cell storage modulus was characterized, by two plateaus, one in the low frequency range, a second one at higher frequencies. The loss modulus instead showed a "bell" shape with a relaxation toward fluid properties at lower frequencies. Mutations shifted the relaxation to higher frequencies, rendering the networks more solid-like. This increase of stiffness with mutations (solid like behavior) was at frequencies around 1 Hz, close to the human heart rate. CONCLUSIONS: These features resulted from a combination of the properties of cytoskeleton filaments and their temporary cross-linker. Our results substantiate that cross-linked filaments contribute, for the most part, to the mechanical strength of the cytoskeleton of the cell studied and the relaxation time is determined by the dissociation dynamics of the cross-linking proteins. The severity of biomechanical defects due to these LMNA mutations correlated with the severity of the clinical phenotype. [ABSTRACT FROM AUTHOR]

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