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In recent years, plastic and metal 3D printing has experienced massive development in the professional and hobby spheres, especially for rapid prototyping, reverse engineering, maintenance and quick repairs. However, this technology is limited by a number of factors, with the most common being the cost and availability of the technology but also the lack of information on material properties. This study focuses on investigating the material properties of PLA, PETG, HIPS, PA, ABS and ASA in order to elucidate their behavior in terms of wear and thermal resistance. The research builds on previous studies focusing on the mechanical properties of these materials and includes wear testing and DMA analysis. Weight loss, frictional forces, and frictional work including relative frictional work are recorded as part of this testing. The storage modulus and loss modulus including tan(δ) were then measured using DMA. [ABSTRACT FROM AUTHOR]

In this work, Gum ghatti-cl-poly(acrylic acid)/CoFe2O4 (GGAACF) hydrogels were synthesized using a free radical polymerization technique, with CoFe2O4 nanoparticles incorporated via a co-precipitation method using nitrates as precursors. Thermal gravimetric analysis (TGA) revealed that the inclusion of CoFe2O4 nanoparticles enhanced the thermal stability of the hydrogels. Swelling studies indicated that the addition of 30 mg of CoFe2O4 nanoparticles maximized water retention. Rheological assessments demonstrated non-Newtonian behavior, with flow curves fitted best by the Power Law model. The incorporation of CoFe2O4 nanoparticles significantly improved the hydrogel's elasticity and viscosity, as evidenced by a higher storage modulus (G′) compared to the loss modulus (G″) across all frequencies, indicating the elastic nature of the hydrogels. The decrease in complex viscosity with increasing frequency confirmed the pseudoplastic properties of the hydrogels, attributed to the random alignment of CoFe2O4 nanoparticles within the matrix. Tan δ values were below unity at all tested frequencies, underscoring the hydrogels' strong elastic properties. These findings highlight the effectiveness of rheological analysis in characterizing the viscoelastic behavior of polymer hydrogels, which can be tailored for various applications. [ABSTRACT FROM AUTHOR]

One of the many intriguing current possibilities for these fibres is the possibility of employing them as a reinforcing component in polymeric structures. This study aims to evaluate the compatibility of bamboo fibre and olive tree leaf powder (OTL) as fillers in epoxy composites throughout a variety of cryogenic exposure lengths (such as 15 min, 30 min, and 60 min). The primary and hybrid composites were produced by compression moulding, with total fibre loadings of 30 weight percent and 3, 6, and 10 weight percent, respectively. The composites were subjected to tensile, bending, impact, and dynamic mechanical analysis (DMA) after production in order to characterise them. An investigation of the morphological analysis of the fractured composites was conducted using a scanning electron microscope (SEM). This study shows that 30-min cryogenic treatments, rather than 15- and 45-min ones, had the best outcomes. It increases in tensile strength by 11.34%, flexural strength by 21.76%, and impact strength by 26.52%. The values for the treated composites are 27.10% and 48.63% higher, respectively, than the tensile and flexural modules. Due to lead compounds' propensity to intensify the mismatch between the fibre and the resin, prolonged cryo-processing times may produce more severe thermal expansions. OTL and bio-composites composed of bamboo interact poorly, which makes them more harmful. The DMA results showed that hybrid composites outperformed primary materials with superior storage moduli, lower loss moduli, and lower damping factors. [ABSTRACT FROM AUTHOR]

This study, provides a comprehensive characterization of biodegradable oil-based magnetorheological fluid (MRF), focusing on its formulation, physical properties, and dynamic behaviour. It has emphasised the importance of using biodegradable oils like Karanja oil and Castor oil for enhanced sustainability and environmental safety. Characterization of MRFs is essential for optimizing their performance in dynamic systems. The physical characterization focused on morphology, sedimentation, and Fourier Transform Infrared Spectroscopy (FTIR) analyses. However, the dynamic characterization incorporates the rheological performance across varied conditions such as strain amplitude, frequency of excitation, temperature, and magnetic field. Sedimentation analysis reveals the superior stability of Carbonyl iron (CI) based MRFs, exhibiting a low sedimentation rate of 1.6% compared to Electrolytic iron (EI) based MRFs of 27% due to its morphological structure. Castor oil with an EI-based sample shows the highest damping capabilities among the MRF samples. The storage modulus increases with the increase in frequency; however, it reduces with the increase in temperature. This research underscores the potential of biodegradable oil-based MRFs with promising rheological properties for vibration attenuation of the dynamic system. [ABSTRACT FROM AUTHOR]

This article considers the effect of protein–starch interaction on the gelling, textural, andsensory properties of keropok lekor used as a fish protein–starch model. A two-level factorial design was employed to analyze the quality and acceptability of different formulations of keropok lekor crackers depending on the ratios of minced fish (MF, 20–50 g (w/w)), sago starch (SS, 10–40 g (w/w)), and water (W, 10–35 g (w/w)). The parameters measured were the onset (T0) and peak (Tp) temperatures of gelatinization, storage modulus (G′), and loss modulus during gelatinization (G″). The samples were rated by a group of 30 panelists during texture profile analysis and sensory evaluation. The most preferred samples had the MF : SS : W ratio of 20 : 10 : 10 and were characterized by the lowest onset and peak temperatures of gelatinization. Therefore, this formulation was singled out as optimal for keropok lekor.

The current study investigates the production of organoclay suitable for use in the base section of a passenger tire with a cap/base tread construction. The process involved the purification and modification of two types of sodium bentonite clay with different mineral characteristics and ion exchange capacities using a single-step process. The modification process of purified bentonite suspensions was performed using a two-tailed long-chain alkyl quaternary ammonium salt surfactant, namely di (hydrogenated tallow alkyl) dimethyl ammonium chloride (AD2HT), and two one-tailed long-chain alkyl quaternary ammonium salt surfactants, namely cetyl-trimethylammonium chloride (CTAC) and octadecylamine chloride (ODA), in relatively low amounts of surfactant (0.95 CEC), along with polyethylene glycol (4% clay) as an auxiliary modifier. X-ray diffraction (XRD) showed that the interlayer spacing of organoclays significantly increases. In addition, the XRD pattern depends on the kind of surfactant and is independent of the type of bentonite clay. The resulting organoclays were added to the tread base section of a passenger tire using the melt masterbatch technique along with a silane coupling agent. An increase in curing maximum torque (8–15%), curing delta torque (6–14%), hardness (2–10%), static modulus 300 (2–18%), and dynamic storage modulus (11–30%) of the rubber composites was observed without significant change of resilience and loss factor of the composite at 2 Phr of organoclay loadings. The organoclays based on the AD2HT modifier exhibited better mechanical properties than those based on the ODA and CTAC surfactants. The dynamic storage modulus of composites increased by about 30% with only 2 Phr of AD2HT-modified bentonites. Furthermore, the performance of the organoclay was found to be independent of the primary particle size, iron content, and ion exchange capacity of the bentonite clay within the studied range. [ABSTRACT FROM AUTHOR]

The curing cycle of natural rubber (NR) with a conventional accelerated sulfur system (CV) generally exhibits three phases. The induction phase, the crosslinking phase, and the reversion phase. Prolonged curing of NR/CV system even at a temperature of 150 °C can show reversion. Many research reports are available in the literature with reference to the reversion behavior and the subsequent network modifications of natural rubber with accelerated sulfur. However, the literature regarding post-reversion curing behavior is scanty. This article describes the post-reversion upturn of natural rubber with a conventional accelerator sulfur system at a higher curing temperature. A network rebuilding after collapsing the initially formed network due to reversion was identified as the primary reason for the post-reversion upturn. The dynamic rheological testing capability of the Rubber Process Analyzer (RPA) was employed to characterize the network formed during curing, reversion and post-reversion phases. The cure-strain sweep data from the RPA indicated that the shear storage modulus (G′) of the broken network increased due to the post-reversion upturn. The chemical crosslink densities of the samples were also found to increase due to the upturn curing behavior. From these experimental results and the information conceived from the previous literature, two plausible mechanisms have been proposed to interpret the post-reversion upturn cure behavior. [ABSTRACT FROM AUTHOR]

Embedding magnetic particles into cement paste produces a smart material in which the rheological properties of the resultant paste can be actively controlled through the use of magnetorheological (MR) principles. This research investigates the rheological behavior of cement-based MR pastes with and without air entrainment to gain a better understanding of the effects of air-entrained bubbles on MR cement pastes. Such information would be critical for the use of such MR pastes in three-dimensional (3-D) concrete printing applications. It is revealed that the incorporation of entrained air increases the MR response, and this effect is related to the bubble-bridge effect. [ABSTRACT FROM AUTHOR]

Increasing demand for high-performance lightweight materials for structural applications poses a challenge to material research and development; subsequently, the expectation of a single lightweight material to sustain itself in a multi-functional environment is also difficult. The present research attempts to address the above-said issue by developing and examining the structural stability of aluminum oxynitride (ALON)-reinforced Kevlar fabric-impregnated epoxy composite. Three different weight percentages 5, 10, and 15 of ALON particles are employed to fabricate the composite sheet through the hand-layup technique. The novel inclusion of ALON particles in the resin-impregnated composite is expected to improve its structural stability. Tensile, flexural, and dynamic mechanical tests are conducted to assess the improved structural stability conforming to standards. The results comprehend the significant improvement of 1.75 times in tensile, 2.59 times in flexural, and 1.28 times in damping characteristics for the higher composition of ALON particles compared to the ALON-free composite. The collective outcome of the study delineates that the novel composite is the right candidate for structural loading. The fracture study conducted through a scanning electron microscope reveals that the failure propagation is followed by collective delamination. [ABSTRACT FROM AUTHOR]

High-performance electrical insulation material can be manufactured using biomass plastic composite (BPC), which is a new type of composite material that is either made up of one or a combination of natural plant fibers/particulates, such as bamboo, cellulose fiber, rice husks, or hemp, and thermoplastic granules. In this study, the BPC composite material that was developed comprised polyethylene (PE), rice husk, and oyster shell. The results of the study showed a significant optimal improvement in the morphological, thermodynamic, and mechanical properties during the addition of 20% to 30% biomass particulates (i.e., rice husk and oyster shell). The thermogravimetric analysis, storage modulus, loss modulus, and damping factor (also known as the tangent of delta [tand]) values showed that compositions of the BPC material exhibited an increasing optimal thermomechanical stability when the composition of the BPC material was made with an increasing mixture of oyster shell, rice husk, and PE compared with that when only rice husk was added to PE. Similarly, the mechanical property of BPC was enhanced with 30% biomass material (i.e., rice husk and oyster shell) and 70% low-density PE plastics. This result indicated that BPC materials can be highly durable and long-lasting, as they are less prone to cracking or breaking. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation 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.)

One of the useful features of 3D-printed specimens of recycled polyethylene terephthalate glycol (R-PETG) is the ability to repetitively develop free recovery as well as the work-generating, shape-memory effect. This behavior is enabled by the R-PETG's capacity to stiffen during cooling, thus allowing for a new temporary shape to be induced. Aiming to devise an explanation for the polymer's stiffening, in this study, the variation in some of the R-PETG's parameters during cooling are emphasized and discussed. The evolution of an R-PETG filament's shape was monitored during room-temperature-bending heating–cooling cycles. Straight-shape recovery and the complete loss of stiffness were observed at the start and the end of heating, respectively, followed by the forced straightening of the filament, performed by the operator, around 40 °C, during cooling. The tests performed by dynamic mechanical analysis disclosed the rise of the storage modulus (E') after 100 °C heating followed by either liquid-nitrogen- or air-cooling to room temperature, in such a way that E' was always larger after cooling than initially. Static tests emphasized a peculiar stress variation during a heating–cooling cycle applied in air, within the heating chamber of the tensile testing machine. Tensile-failure tests were performed at −10 °C at a rate of 100 mm/min, with specimens printed at various deposition directions between 10 and 40° to the transversal direction. The specimens printed at 40°, which had the largest ultimate strains, were broken with tensile rates between 100 and 500 mm/min. Deformation rate increase favored the shift from crazing to delamination failure modes. The correlation between the structural changes, the sharp E' increase on heating, and the stiffening induced by cooling represents a novel approach that enables the use of 3D-printed R-PETG for the fabrication of the active parts of low-priced lightweight resettable actuators. [ABSTRACT FROM AUTHOR]

The heterogeneous nucleation process of polypropylene (PP)/high density polyethylene (HDPE)/thermoplastic elastomer (POE) composites was realized through blending modification, and characterization techniques, including scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and dynamic mechanical analysis, were used to analyze the pattern of the impact of modified dicyclohexyl-terephthalamide (TMB-5) on the mechanical properties and thermal stability of the PP/HDPE/POE composites. The results indicated that the modified TMB-5 was advantageous to the improvement of the mechanical properties and thermal stability of the high-temperature (cooking temperature)-resistant PP/HDPE/POE composites. When the amount of added modified TMB-5 was 0.4%, the impact strength and tensile strength of the PP/HDPE/POE composites increased to 36.3 kJ/m2 and 31.7 MPa, respectively, which were, respectively, 99.5% and 8.5% higher than those of the materials prepared when the amount of added modified TMB was 0.1%. The materials had higher storage modulus in room-temperature and high-temperature environments: 2,438.2 MPa (room temperature), 1,103.9 MPa (120°C), and 1,054.8 MPa (140°C). In addition, the capability of the PP/HDPE/POE composites to crystallize was improved continuously, and the crystallinity increased considerably. At the same time, the crystallization and melting temperatures increased, β-crystal formation was induced, and glass transition temperature increased, thus effectively improving the mechanical properties and thermal stability of the high-temperature (cooking temperature)-resistant PP/HDPE/POE composites.

Using the dynamic mechanical thermal analysis (DMTA) method, the frequency dependence of dynamic mechanical properties of cement asphalt (CA) binders were examined within the testing frequency range between 0.1 and 100 Hz in this study. Based on the time-temperature superposition (TTS) principle, the master curves of storage modulus (E′), loss modulus (E″), and loss factor (tanδ) of CA binders within a wide frequency range from 1 × 10−5 to 1 × 1010 Hz were obtained. The results showed that the E′ , E″ , and tanδ of CA binders were highly sensitive to the frequency due to the incorporation of asphalt. The value of E′ rose as the frequency increased, whereas E″ and tanδ showed different trends as the frequency increased. Storage modulus rising factor ΔE′ and peak value of loss factor tanδmax could be used to characterized the frequency dependence of dynamic mechanical properties. A simple solid model with fractional derivation was established to characterize the dynamic viscoelastic behavior of CA binders and was in excellent agreement with experiment data over both testing and a wide range of frequency. Correlations were observed between model parameters and asphalt content of CA binders. Our results contribute to the current field by providing the evidence for the dynamic mechanical properties estimation of CA mortar under various loading frequency. [ABSTRACT FROM AUTHOR]

The deformation capacity conditions several processes in cement-based materials, including workability and structural build-up. However, the origins of this deformation capacity present some ambiguities. This paper aims to contribute to improving the comprehension of the deformation capacity of fresh cement pastes. For this, the effect of water-to-cement ratio (w/c) and superplasticizer (SP) dosage on the viscoelastic properties of cement paste is examined using oscillatory rheology and yield stress measurements. It appears that water to cement ratio affects slightly the critical strain at the end of the linear viscoelastic domain (LVED) and strongly the storage modulus. The addition of superplasticizer seems to have a strong effect on the critical strain. In addition, it was shown that the critical strain at the end of the LVED is associated with strong physical forces (colloidal forces enhanced by early hydrates formation), while the transition strain at the flow onset is due to large structural reorganizations. [ABSTRACT FROM AUTHOR]

The present work attempts to estimate the impact of graphene and carbon fabric on the dynamic‐mechanical properties of epoxy nanocomposites with different weight percentages. By applying an oscillatory force to a composite, its response is measured, and by calculating the viscosity and the stiffness in relation to the temperature, time, or frequency, valuable information can be realized. It helps to identify "thermal transitions" occurring in polymers. The complex modulus shows the resistance of the composites to deformation caused by viscous and elastic effects. Though dynamic mechanical analysis (DMA) is used for the depiction of temperature‐dependent viscoelastic properties, in this investigation, the objectives were multi‐fold. It is aimed at understanding the role of carbon fabric and the incorporation of 1 wt% of graphene nanoplatelet (GNP) in the epoxy matrix, and the effect of 0.5 to 5 wt% of GNP. The dynamic mechanical properties, including storage modulus, loss modulus, and damping factor, are examined across a temperature range of 25–250°C. Based on the findings, the storage modulus of the composites exhibits a range between 2000 and 9000 MPa. Notably, the epoxy composite containing 1 wt% GNP filler demonstrates the highest storage modulus. The details of mechanisms involved in DMA measurement are schematically summarized. Highlights: Epoxy‐GNP and Epoxy‐GNP‐carbon fabric composites were fabricated.Storage modulus of composites does not show much dependence on the GNP.An increase in storage modulus by 05 times is observed in the ECG1 composite.The loss modulus of EC and EG1 composite is much higher. [ABSTRACT FROM AUTHOR]

In underground filling mining, freshly prepared cemented gangue-fly ash backfill (CGFB) slurries are typically piped into the gobs. The rheological properties of backfill slurry during pipeline transportation have a direct impact on the transportation characteristics, which in turn affect pipeline blockage and wear. In this paper, the rheological behavior and viscoelastic-plastic properties of CGFB during pipeline transportation are investigated. The effects of different solid content and cement content on resistivity were tested experimentally, and their viscoelasticity and plasticity were analyzed. The results show that with the increase in solid phase content and cement content, the viscosity, yield stress, and energy storage modulus of the materials showed an increasing trend. The viscosity and yield stress of the material both increased, reaching 32.77% and 51.22%, respectively. It was found by the dynamic shear test that in the low-strain region, the material showed a more significant elastic nature of the solid, while in the high-strain region, the viscosity of the material gradually increased. Cement has a substantially lower resistivity than fly ash and gangue, and with the increase in solid concentration, the resistivity of the material shows an increasing trend. With the increase in cement content, the resistivity generally shows a decreasing trend, but it should be noted that the resistivity change trend may tend to stabilize after the cement content exceeds 12%. The study's findings can aid in understanding the rheological properties of CGFB and its viscoelastic-plastic behavior during the underground filling and conveying process, which can provide a reference basis for research and application in related fields. [ABSTRACT FROM AUTHOR]

Poly(ether-ketone)/fly ash (FA) composites reinforced with 0-30 wt% FA were fabricated using ball milling followed by hot compaction. The composites were investigated for mechanical and viscoelastic properties. Scanning electron microscopy revealed excellent dispersion and good adhesion of FA particles with the matrix. The addition of FA increased the microhardness by 70% and the storage modulus (below glass transition) by 75%. The reinforcing efficiency was better above the glass transition, which increased to around 177% at 250°C. This research indicates that the FA can be used as an alternative reinforcement of costly ceramic powder for the electronic packaging substrate or printed circuit board applications. [ABSTRACT FROM AUTHOR]

Copyright of China Rubber Industry is the property of Editorial Office of China Rubber Industry 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 emerging need for a sustainable environment prompts the research community to develop functional materials with bio‐ and organic waste. This research advocates biodegradable waste management and its performance evaluation. The involvement of Caesalpinia decapetala (CD) as a potential reinforcement in the epoxy matrix and its analytical evaluation of thermal stability are novel ideas for disposing of bio and organic waste. Three different variants (10, 20, and 30 wt%) of CD seed particles are used to develop the epoxy composite, and further, their influence on dynamic mechanical characteristics such as damping type, loss modulus, and storage modulus has been investigated. The results corroborate that the higher CD seed content (30 wt%) in the epoxy matrix enhances the storage modulus, loss modulus, and damping on a scale of 1.14, 1.25, and 1.07 times that of the neat epoxy matrix. The reason behind the improved dynamic properties has been validated through theoretical modeling. A substantial increment in the degree of entanglement and activation energy in the band of 8.33 × 10−3 moles/m3 and 20.201 kJ/mol, respectively, in comparison with neat epoxy, is considered to be good authentication for the thermal stability of the CD 30 specimen. The analytical prediction of storage modulus is executed with five different models, whereas damping behavior is executed with two different models. The analytically estimated results are matched with the experimental ones, and we conclude that they are in fair agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

The mechanical properties of polymeric membranes are critical factors for a successful and durable application in water treatment technologies. Fabricating membranes with optimal mechanical properties require delicate balancing between material, additives, processing conditions, porosity, and many other variables. Several variables to be optimized demands detailed experimental and computational investigations. The design of experiments (DOEs) technique using a validated framework with a computational model for the prediction of the elastic behavior can lower the number of conducted experiments for optimal membrane fabrication conditions. In this study, optimization of the elastic modulus of polymeric membranes is performed using DOE with computational modeling and validated with experiments. The optimum storage modulus of polymeric nano‐filled membranes is determined at an operating temperature of 35°C. DOE is employed with a three‐factor–three‐level problem. The Taguchi DOE is utilized to obtain the experiments scheme, followed by the prediction of the storage modulus and fabrication of the polymeric nano‐filled membrane with the optimum modulus. Predicted results demonstrate that the modulus of polyether sulfone (PES) reinforced with 0.3 wt.% halloysite nanotubes (HNTs) is the optimum combination. The fabricated PES/0.3 wt.% HNT membrane is in good agreement with the predicted modulus with a percentage error of 3%. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants 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 comfort of walking depends heavily on the shoes used. Consequently, the midsole of shoes is designed in such a way that it can dampen force peaks during walking. This significantly increases the overall wellness during walking. Therefore, the midsole usually consists of rubber-like polymers, such as polyurethane and ethylene-vinyl acetate copolymer. Furthermore, the manufacturing process of these polymers results in a foam-like structure. This further enhances the damping behavior of the material. Nevertheless, it would be desirable to find a cheap and sustainable method to enhance the damping behavior of the shoe midsole. The purpose of this work is to see if hemp fibers, which are part of the polymer matrix material, could improve the stiffness without losing the damping behavior. The mechanical properties of such prepared fiber-reinforced composites were characterized by quasi-static tensile testing and dynamic mechanical analysis. The mechanical properties were examined in relation to the fiber type, weight fraction, and type of polyurethane used. Furthermore, the investigation of the embedding of these fibers in the polymer matrix was conducted through the utilization of optical and electron microscopy. [ABSTRACT FROM AUTHOR]

Third-degree burn injuries pose a significant health threat. Safer, easier-to-use, and more effective techniques are urgently needed for their treatment. We hypothesized that covalently bonded conjugates of fatty acids and tripeptides can form wound-compatible hydrogels that can accelerate healing. We first designed conjugated structures as fatty acid–aminoacid1–amonoacid2–aspartate amphiphiles (Cn acid–AA1–AA2–D), which were potentially capable of self-assembling into hydrogels according to the structure and properties of each moiety. We then generated 14 novel conjugates based on this design by using two Fmoc/tBu solid-phase peptide synthesis techniques; we verified their structures and purities through liquid chromatography with tandem mass spectrometry and nuclear magnetic resonance spectroscopy. Of them, 13 conjugates formed hydrogels at low concentrations (≥0.25% w/v), but C8 acid-ILD-NH2 showed the best hydrogelation and was investigated further. Scanning electron microscopy revealed that C8 acid-ILD-NH2 formed fibrous network structures and rapidly formed hydrogels that were stable in phosphate-buffered saline (pH 2–8, 37 °C), a typical pathophysiological condition. Injection and rheological studies revealed that the hydrogels manifested important wound treatment properties, including injectability, shear thinning, rapid re-gelation, and wound-compatible mechanics (e.g., moduli G″ and G′, ~0.5–15 kPa). The C8 acid-ILD-NH2(2) hydrogel markedly accelerated the healing of third-degree burn wounds on C57BL/6J mice. Taken together, our findings demonstrated the potential of the Cn fatty acid–AA1–AA2–D molecular template to form hydrogels capable of promoting the wound healing of third-degree burns. [ABSTRACT FROM AUTHOR]

We report on shear-stress relaxation of melts of poly(propyleneimine) (PPI) dendrimers of different generations (G2–G5). The aim of this study was to confirm our previous conclusion in Sheveleva et al. [Phys. Chem. Chem. Phys. 24, 13049–13056 (2022)] for carbosilane dendrimers that an impenetrable inner region leads to the manifestation of the crowded environment effect. The systems of PPI dendrimer melts are studied using atomistic molecular dynamics simulations. The time and frequency dependencies of the dynamic shear-stress modulus are investigated. The results are in good agreement with the available rheological experimental data for G2–G4 PPI. We have found that the crowded environment effect does not manifest itself in the mechanical relaxation of G4 PPI dendrimers in contrast to G4 carbosilane dendrimers. Despite their similar topology and close sizes, G4 PPI does not form an impenetrable core. The G5 PPI dendrimer has an impenetrable inner region, and the crowded environment effect is observed. As in carbosilane dendrimers, the maximal time of mechanical relaxation is increased due to the crowded environment effect. However, the opposite situation is for the rotational diffusion of the G5 PPI dendrimers. In contrast to carbosilane dendrimers, the rotational mobility of G5 PPI significantly slows down even taking into account the increase in the dendrimer size. The hydrogen bonding between PPI dendrimers affects the mechanical relaxation at high frequencies (short times) and enhances with growing G. [ABSTRACT FROM AUTHOR]

A novel polymer blend gel electrolyte was made based on two crystallizable polymers of poly(vinylidene fluoride) and nylon-11 in dielectric aprotic organic solvent of propylene carbonate (PC) and its mixture with ethylene carbonate (EC) with and without two different salt lithium tetrafluoroborate (LiBF4) and lithium bis-oxoborate (LiBOB). The melting point of nylon-11 comes down in the blend with PVDF in the presence of Li-salt. The unsalted samples show lower gel melting and gelation temperatures of PVDF with an increase in nylon-11 content in EC:PC 2:1 solvent mixture. The storage modulus increased with nylon-11 content and was responsible for more entanglement density through the formation of dense gel network structures. The conductivity falls rapidly at below room temperature because EC solidifies at 40 °C, which enhances the viscosity and motion of lithium ions. The conductivity is higher at room temperature for the EC:PC: 2:1 dielectric solvent mixture. The conductivity is lower in the blend gel, as the nylon-11 solution crystals hinder the motion of ions. Morphological investigation reveals that PVDF unsalted gel is spheroidal, whereas it is fibrillar, intertwined ball shape, and elastic in nature for salted gels. Fibrils become thicker and denser in the presence of nylon-11 and lithium salt. Overall, blended gel electrolytes have a thermal transition of melting/gelation temperature that does not affect conductivity, but storage modulus is much enhanced through inter-networking gelation structural integrity. Highlights: Gel electrolyte blends. Lithium salts. Ionic conductivity. Storage modulus. Morphology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this study, an inorganic retarder and a synthesized dispersant (based on PCE) were used to improve the retention and workability of alkali-activated ground granulated blast furnace slag (GGBFS), with NaOH as the sole activator. The objective of the study was to formulate pumpable concrete mixtures with workable time of more than 90 min. The prolonged retention in slump was attained by the addition of the retarder. The effect of the dispersants, synthesized with different monomer to macromonomer ratios, on the workability of the paste was investigated by analyzing the fundamental rheological parameters. The addition of dispersant reduced the initial storage modulus and improved the workability of the alkali-activated paste mixtures. The interaction between the dispersant and NaOH-activated GGBFS systems was investigated by means of adsorption studies and zeta potential measurements. The dispersing ability and the amount adsorbed on GGBFS increased with an increase in the anionic charge of the dispersant. Zeta potential measurements suggested that the dispersion mechanism is primarily due to steric hindrance. Concrete mixtures of compressive strength in the range of ordinary concrete with pumpable workability for 90 and 120 min were achieved with the addition of both retarder and dispersant. The study concludes that a retarder is necessary to prolong the workable times, whereas a dispersant with a higher anionic charge is required to improve the workability of sodium hydroxide-activated GGBFS mixtures.

Calcium-silicate-hydrate (C–S–H) is the most important phase in concrete materials, and plays a dominant role in the time-dependent properties of concrete. However, the evolution of mechanical behavior of C–S–H gels over time remains unclear, leading to a lack of fundamental understanding of the mechanical behavior of cementitious materials over time. In this study, nanoindentation continuous stiffness measurement (CSM) is adopted to probe the time-dependent behavior of C–S–H gel. Furthermore, the corresponding mechanism was analyzed and discussed. The results show that C–S–H structure units would occur preferred orientation arrangement under external load, and the process of completing the preferred orientation arrangement is expedited under greater load, resulting in decreased fluctuations in storage modulus and hardness. For different types of C–S–H, when the same load function is applied, the C–S–H gel with higher packing density first completes the preferred orientation arrangement. Besides, the hardness of C–S–H measured by the CSM was more sensitive to the indention time or depth than the storage modulus. Overall, this research provides direct evidence for C–S–H re-orientation from a micromechanical perspective.

Physiological loading of knee cartilage is highly dynamic and may contribute to the progression of osteoarthritis. Thus, an understanding of cartilage's dynamic mechanical properties is crucial in cartilage research. In this study, vibrometry was used as a fast (2 h), noncontact and novel alternative to the slower (30 h), traditional mechanical and biochemical assays for characterization of cartilage from the condyle, patella, trochlear groove and meniscus. Finite-element models predicted tissue resonant frequencies and bending modes, which strongly correlated with experiments (R2 = 0.93). Vibrometry-based viscoelastic properties significantly correlated with moduli from stress relaxation and creep tests, with correlation strengths reaching up to 0.78. Loss modulus also strongly correlated with glycosoaminoglycan (GAG) content. Dynamic properties measured by vibrometry significantly differed among various knee cartilages, ranging between 6.1 and 56.4 MPa. Interestingly, meniscus viscoelastic properties suggest that contrary to common belief, it may lack shock absorption abilities; instead, condylar hyaline cartilage may be a better shock absorber. These data demonstrate for the first time that vibrometry is a noncontact approach to dynamic mechanical characterization of hyaline and fibrocartilage cartilage with concrete relationships to standard quasi-static mechanical testing and biochemical composition. Thus, with a single tool, vibrometry greatly facilitates meeting multiple regulatory recommendations for mechanical characterization of cartilage replacements.

The relationship between crosslinking density and storage modulus of chloroprene rubber (CR) / ethylene-propylene-diene rubber (EPDM) blend was studied and the fitting model was established. The relationship between the crosslinking density, storage modulus and stress relaxation properties of each component in the blended rubber was also investigated. The results showed that the applicable temperature range of the model was 35-80 ℃ and the crosslinking density of the two phases were linearly related to the storage modulus. When m(CR)/m(EPDM) was 70/30, the predicted value of the storage modulus model of CR/EPDM blend was close to the measured value, which proved that the model had high reliability. The effect of CR phase on the total storage modulus of CR/EPDM blend was greater. The stress relaxation property of the blend had a linear relationship with the crosslinking density and storage modulus of each component.

The morphology of dispersed particles has been proven to have a significant impact on performance of electrorheological (ER) materials, while there is a lack of relevant research on its impact on the properties of electrorheological elastomers (EREs). In this study, the TiO2 particles with spherical, short rod, and long rod shape were fabricated with sol-gel method, and the EREs were prepared with these three kinds of particles as dispersion phase. Particle characterization results show that the rod-shape TiO2 particles with larger average size exhibit a combination of anatase and brookite phase. The viscoelastic properties of three types of EREs under varying strain amplitude and shear frequency were tested. The results indicate that the long rod-shape TiO2 particles filled EREs shows higher storage modulus G' and higher relative ER effect within the electric field from 0 to 3 kV/mm. The observations indicate the use of rod-shape TiO2 particles in the form of brookite phase may help enhance the ER properties of elastomers. The investigation contributes to the designing, preparation, and application of anisotropic ERE. [ABSTRACT FROM AUTHOR]

For bonded Fibre Reinforced Polymer (FRP) strengthening systems in civil engineering projects, the adhesive joint performance is a key factor in the effectiveness of the strengthening; however, it is known that the material properties of structural epoxy adhesives change with temperature. This present paper examines the implied relationship between the curing regimes and the storage modulus response of the adhesive using a Machine Learning (ML) approach. A dataset containing 157 experimental data collected from the scientific papers and academic theses was used for training and testing an Artificial Neural Network (ANN) model. The sensitivity analysis reveals that the curing conditions have a significant effect on the glass transition temperatures (Tg) of the adhesive, and consequently on the storage modulus response at elevated temperatures. Curing at an extremely high temperature for a long time does not, however, guarantee a better thermal performance. For the studied adhesive, curing in a warm (≥ 45°C) and dry (near 0 % RH) environment for 21 days is recommended for practical applications. A software with a Graphical User Interface (GUI) was established, which can predict the storage modulus response of the adhesive, plot the corresponding response curve, and estimate the optimum curing condition. [ABSTRACT FROM AUTHOR]

In this article, polymer nanocomposites of polyisoprene with specific blend ratio 25/75 wt% of cis‐polyisoprene (CPI) and trans‐polyisoprene (TPI) with varying concentration (0.1, 1, and 5 wt%) of so synthesized silver nanoparticles (AgNPs) have been prepared and characterized through x‐ray diffraction, transmission electron microscope and scanning electron microscope. Experimental results on dynamic mechanical analysis show that addition of AgNPs to CPI/TPI blend reduces storage modulus, activation energy and fragility while enhances damping, however, glass transition temperature remains unaffected. Other mechanical properties such as toughness and tensile strength first increases on addition of AgNPs in the CPI/TPI blend, but a decrease is noticed on further increase of AgNPs concentration. Young's modulus shows a drastic decrease on addition of AgNPs into CPI/TPI blend, however, an increase is observed at higher concentration of AgNPs. Thermal analysis results show that thermal conductivity enhances with the enhancement in concentration of AgNPs into CPI/TPI blend. Highlights: Addition of AgNPs into CPI/TPI blend reduces storage modulus, activation energy and fragilityIncorporation of AgNPs into CPI/TPI blend enhances damping but does not change glass transition temperature.Increase in concentration of AgNPs in CPI/TPI blend increases the thermal conductivity. [ABSTRACT FROM AUTHOR]

The purpose of this research is to improve the dynamic-mechanical properties of the polypropylene filled by artichoke stem (AS) particles and wollastonite (W) in different weight fractions. The effect of weight ratios of fillers in polypropylene was mathematically modeled using the data obtained as a result of the experimental work. In the modeling phase, multiple nonlinear neuro-regression analysis was used. In this context, proposed linear and nonlinear models have been examined by performing R2 training, R²adjusted, R²testing, and boundedness check. The models that satisfy these four criteria were selected as the objective functions for the optimization phase. Finally, Modified Differential Evolution Algorithm was used to obtain maximum storage modulus and loss modulus by adjusting weight percent ratio of artichoke stem particle and wollastonite. The experimental results and the modeling optimization results showed that when the polypropylene-artichoke stem particle-wollastonite hybrid polymer composite was used instead of other non-hybrid polymer composite, the storage modulus and the loss modulus improved by approximately 40%. [ABSTRACT FROM AUTHOR]

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Kodo millet's popularity grows due to its diverse applications and health benefits, primarily as a starch source for industries like food processing, requiring modifications to overcome raw starch limitations. In this study, raw kodo starch underwent treatment with cold plasma, varying in voltage (10, 20, and 30 kV) and duration (10, 20, and 30 min). The treated samples were designated as S1 to S9. The results showed that the modified starch exhibited significantly higher G' and G" values compared to the control sample. Three different models were attempted to describe the flow behavior, with the most suitable model selected. This analysis led to an increase in yield stress from 86.55 to 217.98 Pa and an increase in the flow index from 0.31 to 0.56 for the modified starch. This understanding of the rheological characteristics of modified starch can be invaluable for innovating new products, blending novel ingredients, and optimizing manufacturing processes. Practical applications: Kodo millet has gained significant popularity in recent times owing to its high fiber content and low glycemic index. In this research, starch extracted from kodo millet underwent plasma treatment, resulting in a modified starch with enhanced functional properties. The study focused on exploring the rheological properties of this treated starch, and the findings revealed notable improvements in dynamic rheological parameters, including the storage modulus, loss modulus, and viscosity of the starch, all of which increased due to the plasma treatment. The enhanced viscosity makes kodo millet starch particularly suitable for a wide range of food applications. This modified starch finds practical use in the preparation of porridges, soups, and as a reliable filling agent in various food products. This emerging technology has captured the attention of food manufacturers in the grain processing sector, offering a means to elevate the quality and desirability of new food products. [ABSTRACT FROM AUTHOR]

The effect of vulcanization accelerators on the structure and properties of rubbers based on Hydrin T6000 epichlorohydrin rubber was studied. As accelerators, we used mercaptobenzthiazole (MBT) in the amount of 1.5 pts. wt., tetramethylthiuram disulfide (TMTD) in the amount of 0.5–1.5 pts. wt., and N,N'‑diphenylguanidine (DPG) in the amount of 0.5–1.5 pts. wt., which represent a triple system of accelerators. The choice of accelerators is based on the possibility of obtaining a vulcanization spatial structure of different sulfide content: thiuram group accelerators promote the formation of mono- and disulfide bonds; guanidine group, polysulfide bonds; and thiazole group, from carbon-carbon to polysulfide with varying degrees of sulfide. According to the results of the study of physical and mechanical properties, the determination of the parameters of the spatial grid, and the study of the dynamic behavior of rubber, differences were revealed owing to the formation of a spatial structure with different types of crosslinks and density. It is shown that rubber containing 1.5 pts. wt. MBT, 0.5 pts. wt. DFG, and 0.5–1.0 pts. wt. TMTD possess the best set of properties owing to the manifestation of a synergistic effect on the formation of a vulcanization network of a certain density and the ratio of poly-, di-, and monosulfide crosslinks. Thus, the use of a group of accelerators with different functional effects makes it possible to obtain vulcanizates with an optimal set of technological and operational properties. [ABSTRACT FROM AUTHOR]

Micromechanical properties of polymeric materials play a critical role in various biological applications in terms of their biocompatibility and mechanical durability. Apart from material properties such as modulus and density, viscoelastic properties play a crucial role during the design and fabrication of devices. Here, we investigated the viscoelastic properties of poly (glycerol sebacate) (PGS), a widely used bioresorbable elastic material, through the nanoindentation technique, configured by the continuous stiffness measurement (CSM) method at frequencies from 10 Hz to 50 Hz. The results revealed that the storage modulus (E') depends on the test frequency and cannot be ignored as the results showed significant changes. Additionally, increasing the curing temperature of PGS specimens between 150 to 170°C allows modifying the storage modulus of samples between 0.52 MPa and 1.05 MPa at 10 Hz. The results were also confirmed using the dynamic mechanical measurements to validate the reliability of the CSM nanoindentation technique. [ABSTRACT FROM AUTHOR]

Poly(12-hydroxystearate) was prepared by polycondensation. Palmitic acid, 3-dimethylaminopropylamine and poly(12-hydroxystearate) were reacted to form a terminated polyhydroxystearate aliphatic amine (HTPF) hyperdispersant. The structure of the product was characterized by IR and ¹H NMR. The dispersion effect of HTPF on carbon black was analyzed by sedimentation experiment and scanning electron microscope. HTPF was added into ABS/carbon black masterbatch, and the effects of the amount of HTPF on the rheological and mechanical properties of ABS/carbon black masterbatch were studied. The results show that the loss modulus and storage modulus of the composites decrease gradually with the increase of HTPF content compared with the pure masterbatch, and the composites appear shear thinning behavior. With the increase of HTPF content, the mechanical properties of the composites gradually improved. When the content of HTPF is 40%, the tensile strength and impact strength of the composite reach the maximum of 45.9 MPa and 8.54 kJ/m²; When the content of HTPF is 50%, the flexural strength of the composites reaches 80.22 MPa. [ABSTRACT FROM AUTHOR]

In this study, we investigated the electrorheological characteristics of a fibrous hydrated magnesium silicate, sepiolite suspension. The sepiolite nanoparticles were heat-treated between 150 and 900 °C, and 2 wt% sepiolite was dispersed in silicone oil. The structural change of the baked particles was analyzed. The effects of the particle loading and applied voltage were evaluated. It was found that the heat-treated sepiolite suspension showed relatively higher viscosity, storage modulus and loss modulus. In addition, as the applied voltage increased, the shear yield stress increased. When a 9 kV/mm direct current (DC) field was applied, a shear yield stress of 16.8 kPa was measured. [ABSTRACT FROM AUTHOR]

The effect of incorporation of micron sized aluminum trihydrate, multi‐walled carbon nanotubes, and graphene nano platelets into glass fiber reinforced epoxy matrix is investigated using dynamic mechanical analysis. The objective of the investigation was to develop polymer central core of high temperature low sag transmission conductor. The effect of individual and hybrid carbon fillers on the viscoelastic properties of the epoxy composites is investigated and discussed. The storage modulus of the glass reinforced epoxy increases by 20% at room temperature due to incorporation of carbon nanofillers. In glass transition region, the increase is higher between 40% and 60% and it varies up to 90% in the rubbery region. Key attributes of carbon filler addition are limited enhancement of storage modulus at room temperature, higher enhancement over glassy, glass transition, and rubbery regions. The carbon fillers extend the temperature range of the glassy region. The cross‐link density, filler efficiency, and degree of entanglement of fibers are estimated to understand the implications of the carbon fillers on the viscoelastic properties. The loss modulus peak of glass epoxy composite increases from 2800 to 3900 MPa with carbon fillers and the increase in glass transition temperature is 47°C. Incorporation of carbon fillers leads to increase of damping factor peak from 0.2 to 0.28. Cole–Cole plots have established the inherent heterogeneity of epoxy systems due to the presence of carbon fillers. Prediction models for storage modulus and damping factor have been proposed to highlight the influence of geometry and size of carbon filler. [ABSTRACT FROM AUTHOR]

The morphology of dispersed particles has been proven to have a significant impact on performance of electrorheological (ER) materials, while there is a lack of relevant research on its impact on the properties of electrorheological elastomers (EREs). In this study, the TiO2 particles with spherical, short rod, and long rod shape were fabricated with sol-gel method, and the EREs were prepared with these three kinds of particles as dispersion phase. Particle characterization results show that the rod-shape TiO2 particles with larger average size exhibit a combination of anatase and brookite phase. The viscoelastic properties of three types of EREs under varying strain amplitude and shear frequency were tested. The results indicate that the long rod-shape TiO2 particles filled EREs shows higher storage modulus G′ and higher relative ER effect within the electric field from 0 to 3 kV/mm. The observations indicate the use of rod-shape TiO2 particles in the form of brookite phase may help enhance the ER properties of elastomers. The investigation contributes to the designing, preparation, and application of anisotropic ERE.

In this study, starch is treated with different concentrations of citric acid (CA, 5, 10, 20, and 30 g/100 g dry basis) which leads to the production of citrate starch. The effect of CA concentration on physio‐chemical, structural, rheological, thermal properties, and digestibility is analyzed. A Fourier transform infrared (FTIR) spectroscopy Stands for FTIR peak at 1728 cm−1 is observed, indicating ester bond formation between CA and starch molecules. A nonsignificant change in the crystalline pattern is observed between native and citrate starch, whereas a decrease in relative crystallinity from 15.75% to 6.91% is observed. With the increase in the degree of substitution, gelatinization decreases, and gelatinization's enthalpy (ΔH) decreases from 13.72 to 9.63 J g−1. The rapid digestible starch (RDS) decreases by CA treatment, whereas slow digestible starch (SDS) and resistant starch (RS) increase significantly from 32.81 g/100 g dry basis to 39.45 g/100 g dry basis and 9.87 g/100 g dry basis to 25.26 g/100 g dry basis, respectively. [ABSTRACT FROM AUTHOR]