Rheological Tests Research Articles

Structural characterization of Porphyra haitanensis extracts and their effects on structure, physicochemical properties, and in vitro digestibility of corn starch

Porphyra haitanensis with many bioactive components has great prospects for application in the functional food, pharmaceutical, and cosmeceutical industries. In this study, two sequentially extracted fractions (PhE1 & PhE2) were isolated and structurally characterized. The results showed that PhE1 was mainly composed of protein (36.82%) and neutral sugar (32.43%), while PhE2 mainly contained neutral sugar (58.70%). Both had galactose as main monosaccharides, PhE2 also contained a small amount of glucose. To widen the application of PhEs in starchy foods, they were added to corn starch (CS) system and co-gelatinized. Rheological tests indicated that PhEs could effectively affect gel strength of CS. The addition of PhEs effectively inhibited the content of leached amylose in CS gelatinization system except those at an addition of 5% PhE1 and 5% PhE2. FT-IR data suggested that PhE1 could improve the short-range order, but PhE2 showed no significant effects. SEM images showed that the pore wall of the composites thickened, and the network structure became relatively ordered. In vitro tests, PhEs significantly reduced the contents of rapidly digestible starch, and PhE1 presented better effects. Therefore, PhEs may be used as potential materials to delay the digestion of CS and related products.

Development and mechanism research of hydrophobic associative polymer drag reducing agents

ABSTRACT The challenge of insufficient proppant transportation capacity in slick water remains unresolved. To tackle this concern, a hydrophobically associating water-soluble polymer (HAWP), characterized by a low molecular weight (MW) of 8.11 × 105 g/mol, was successfully synthesized via a photo-initiation method. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The results show that in comparison to conventional drag reducers in slick water with an average MW of approximately 1 × 107 g/mol, HAWP demonstrates significantly reduced MW. The rheological test results indicate that upon addition of sodium dodecyl benzene sulfonate (SDS, 200 mg/L) to the HAWP solution (0.3 wt%), the storage modulus experienced a substantial increase from 0.14 Pa to 7.42 Pa, demonstrating enhanced mechanical properties. Meanwhile, drag reduction (DR) tests showed that the efficiency of drag reduction achieved by the polymer system (PS) drag reducer was comparable to that of conventional linear polymers. This research achievement effectively addresses the challenges of low molecular weight and resistance reduction encountered in previous endeavors.

Tuning Lubrication Performance of Phase‐changing Emulsion‐filled Gels by Sugar alcohols

Lubrication by hydrogels is proving to be an emerging area in colloid science. Although oil‐driven friction reduction is predominant in literature, emulsion gel‐based lubrication has attracted very little attention to date. We hypothesize that an interplay of viscolelasticity and oil volume fraction may modulate lubricity of emulsion‐filled gels. Herein, phase‐change gelatin‐based emulsion‐filled gels with different sugar alcohol and oil droplet concentrations (0‐30 wt%) were tested for their lubrication performance. The rheological and tribological tests were analysed in conjunction with spectroscopic and structural characterizations in order to reveal structure‐function relationship. Structural characterizations demonstrated that hydrogen bonding was enhanced in pure gelatin gels with the increase of sugar alcohol (glycerol)‐replacement time, which enhanced the storage modulus (G') of the gel networks. Emulsified droplets served as active fillers further strengthening the G’ and strikingly the presence of glycerol reduced the thermo‐responsiveness of the emulsion‐filled gels. Emulsion‐filled gels containing sugar alcohols, irrespective of their type, can greatly reduce the friction coefficients (μ) between hydrophobic surfaces in the boundary and mixed regimes versus the systems without sugar alcohols. In the hydrodynamic regime, the friction coefficient of the system was proportional to the second plateau shear viscosity, regulated by the oil content.This article is protected by copyright. All rights reserved.

Improving Water-Based Drilling Mud Performance Using Biopolymer Gum: Integrating Experimental and Machine Learning Techniques.

Drilling through shale formations can be expensive and time-consuming due to the instability of the wellbore. Further, there is a need to develop inhibitors that are environmentally friendly. Our study discovered a cost-effective solution to this problem using Gum Arabic (ArG). We evaluated the inhibition potential of an ArG clay swelling inhibitor and fluid loss controller in water-based mud (WBM) by conducting a linear swelling test, capillary suction timer test, and zeta potential, fluid loss, and rheology tests. Our results displayed a significant reduction in linear swelling of bentonite clay (Na-Ben) by up to 36.1% at a concentration of 1.0 wt. % ArG. The capillary suction timer (CST) showed that capillary suction time also increased with the increase in the concentration of ArG, which indicates the fluid-loss-controlling potential of ArG. Adding ArG to the drilling mud prominently decreased fluid loss by up to 50%. Further, ArG reduced the shear stresses of the base mud, showing its inhibition and friction-reducing effect. These findings suggest that ArG is a strong candidate for an alternate green swelling inhibitor and fluid loss controller in WBM. Introducing this new green additive could significantly reduce non-productive time and costs associated with wellbore instability while drilling. Further, a dynamic linear swelling model, based on machine learning (ML), was created to forecast the linear swelling capacity of clay samples treated with ArG. The ML model proposed demonstrates exceptional accuracy (R2 score = 0.998 on testing) in predicting the swelling properties of ArG in drilling mud.

Self-assembled lyotropic liquid crystals from natural surfactant: A study on their structural, rheological and antimicrobial behaviour

Soft self-assembled systems with smart functions have been explored over the past decades for diverse applications. However, the toxicity of synthetic surfactant based self-assembled systems and their stability always remain a point of concern. There is always a great quest to find an alternative to overcome such shortcomings of self-assembled systems. Hence, in this context, we made an effort to engineer self-assembled lyotropic liquid crystals (LLCs) using different concentrations of the medicinal plant Glycyrrhiza glabra L. in the nonaqueous polar media of glycerol, ethylene glycol and formamide. These nonaqueous solvents with considerable polarity, high cohesive energy, dipole moment and hydrogen bonding ability, not only offer the perfect environment for self-assembly, but also provide longtime stability. Nematic lyotropic ordering is obtained for studied systems at different concentrations of Glycyrrhiza glabra L./ nonaqueous solvents as confirmed via polarising optical microscopy (POM) and X-ray diffraction (XRD) analysis. Electrostatic and hydrogen bonding interactions among polar solvents and amphiphilic Glycyrrhiza glabra L. molecules could be responsible for nematic ordering. FTIR spectroscopy is employed to confirm the hydrogen bonding in LLCs. The prepared LLCs are studied through static, dynamic rheology under the shear range 1–100 s-1 to explore their fluidic behaviour and establish correlation with structural parameters. The studied LLC systems from three solvents exhibit non-Newtonian shear thinning behaviour at all concentrations. The dynamic rheology tests indicate the elastic behaviour of all LLC systems. LLCs derived from glycerol exhibit soft-solid gel-like behaviour, while weak gel-type behaviour is observed for ethylene glycol and formamide-based LLCs. Considering the medicinal value of prepared LLCs, their antibacterial activity has been checked against the gram-positive bacteria Bacillus subtilis. LLC phases show strong antibacterial activity, about 2–3 times better than that of the standard drug streptomycin used for this study.

Evaluation of warm mix effect in laboratory using a self-developed WMA additive Alube

In response to the problems of high mixing temperatures and energy consumption of polymer-modified asphalt mixtures in road construction, a surfactant-based warm mix additive ‘Alube’ was developed. The warm mix SBS-modified asphalt and its mixture were prepared. Their rheological performance and chemical structure were analysed by the rheological and microscopic tests. The active mixing power (P) of asphalt mixtures were examined by the variable speed mixing (VSM) test. The mixing flowability model was then established to evaluate the warm mix effect. The results indicated that the mixing flowability of asphalt mixtures obeyed the linear Bingham visco-plastic model, and the slope and intercept of the flow straight characterised the mixing viscosity and plastic limit. It is evaluated that 0.7% Alube1 and Evotherm reduced the mixing temperature of SBS-modified asphalt mixture by 14°C and 12°C, respectively. Moreover, Alube1 is suitable for a wide range of applications through warm mix asphalt technology.

Research on Low-Cost High-Viscosity Asphalt and Its Performance for Porous Asphalt Pavement.

To develop a cost-effective, high-viscosity asphalt for porous asphalt pavement, we utilized SBS, tackifier, and solubilizer as the main raw materials, identified the optimal composition through an orthogonal experiment of three factors and three levels, and prepared a low-cost high-viscosity asphalt. We compared its conventional and rheological properties against those of rubber asphalt, SBS modified asphalt, and matrix asphalt, employing fluorescence microscopy and Fourier transform infrared spectroscopy for microstructural analysis. The results indicate that the optimal formula composition for high-viscosity asphalt was 4-5% styrene-butadiene-styrene (SBS) + 1-2% tackifier +0-3% solubilizer +0.15% stabilizer. The components evenly dispersed and the performances were enhanced with chemical and physical modification. Compared with SBS modified asphalt, rubber asphalt, and matrix asphalt, the softening point, 5 °C ductility, and 60 °C dynamic viscosity of high-viscosity asphalt were significantly improved, while the 175 °C Brookfield viscosity was equivalent to SBS modified asphalt. In particular, the 60 °C dynamic viscosity reaches 383,180 Pa·s. Rheological tests indicate that the high- and low-temperature grade of high-viscosity asphalt reaches 88-18 °C, and that high-viscosity asphalt has the best high-temperature resistance to permanent deformation and low-temperature resistance to cracking. It can save about 30% cost compared to commercially available high-viscosity asphalt, which is conducive to the promotion and application of porous asphalt pavement.

Investigation of Rheological and Physical Properties of SBS and WCO Composite Modified Bitumen

Nowadays, the use of waste materials in various industries is becoming widespread in order to promote waste recycling. Thus, scientists are researching the use of waste materials in bitumen modification. In this study, it was aimed to investigate the effect of waste cooking oil (WCO) on the physical and rheological properties of unaged Styrene-Butadiene-Styrene modified bitumen (SBSMB) by adding WCO at different ratios (1, 3, 5, 7, and 9%) to SBS modified bitumen. Accordingly, rotational viscosity (RV) tests and rheological tests with dynamic shear rheometer (DSR) based on the determination of complex shear modulus (|G*|) and phase angle (δ) were conducted along with the traditional bitumen tests. As a result of the experimental study, it was observed that adding WCO increased the workability and fatigue resistance of SBSMB, however, decreased its rutting resistance. Therefore, the mixing and compaction temperatures of SBSMB can be decreased by adding low amounts of WCO without excessive performance loss. Thus, during the construction of asphalt pavements, environmental damage can be reduced by utilizing waste materials and reducing CO2 emissions.

Improving Sag Resistance in Geopolymer Coatings Using Diatomite Filler: Effects on Rheological Properties and Early Hydration.

The reduction in the rheological parameters and dissolution rate of precursors in geopolymer coatings during early hydration significantly contributes to sagging. This study aims to improve the sag resistance of these coatings by incorporating diatomite filler. Rheological testing was conducted to assess the impact of diatomite and its concentration on the yield stress, plastic viscosity, and thixotropy of the geopolymer coatings. The results indicated that diatomite's large specific surface area and high reactivity have a significant influence on the rheological parameters and early dissolution rate of precursors. With a diatomite concentration of 1.1%, the coating exhibited a yield stress of 2.749 Pa and a plastic viscosity of 0.921 Pa·s, maintaining stability, homogeneity, and no sagging at a thickness of 600 μm. Furthermore, the highly active SiO2 in diatomite participates in the secondary hydration reaction of the geopolymer materials led to the formation of substantial C-(A)-S-H gel. This gel enhances internal interconnectivity within the coating, thereby improving its rheological and mechanical properties.

Optimizing the design parameters for chamotte particle‐reinforced geopolymers

AbstractThis study delved into the utilization of chamotte particles in varying contents (0–50 wt%) as reinforcing agents in both fresh and hardened states within potassium‐based geopolymer (KGP) composites. Although the previous research predominantly underscored the high‐temperature stability of chamotte in composites subjected to extreme conditions, this study focuses on expanding their potential applications at ambient temperature. The experimental findings showed that the flowability of the pastes experienced a slight reduction up to 20 wt% chamotte, followed by a substantial decrease, ultimately resulting in complete shape retention at 50 wt%. Squeeze flow and standard rheological tests supported these observations, revealing elevated work‐to‐squeeze values peaking at 1.3 J. X‐ray diffraction data showed that crystallinity prevailed in chamotte, establishing its efficacy as a nonreactive reinforcement. In the hardened state, the inclusion of chamotte enhanced the mechanical properties of the composites, specifically compressive, flexural, and splitting tensile strengths, reaching up to 61.7, 13.2, and 5.6 MPa, respectively. Young's modulus (E) and shear modulus (G) also exhibited an upward trend with increasing chamotte content, reaching values of up to 17.7 and 7.7 GPa at 50 wt%, respectively. Scanning electron microscopy (SEM) analysis validated particle interlocking and crack‐bridging mechanisms. In general, this study highlights the effectiveness of chamotte particles in improving the mechanical properties of KGP composites at room temperature. It also emphasizes the necessity of considering the mentioned parameters in the design of particulate‐reinforced geopolymer compositions for diverse applications.

Enhancing Mechanical Performance of High-Density Polyethylene at Different Environmental Conditions with Outstanding Foamability through In-Situ Rubber Nanofibrillation: Exploring the Impact of Interface Modification.

In this study, we utilized in situ nanofibrillation of thermoplastic polyester ether elastomer (TPEE) within a high-density polyethylene (HDPE) matrix to enhance the rheological properties, foamability, and mechanical characteristics of the HDPE nanocomposite at both room and subzero temperatures. Due to the inherent polarity differences between these two components, TPEE is thermodynamically incompatible with the nonpolar HDPE. To address this compatibility issue, we employed a compatibilizer, styrene/ethylene-butylene/styrene copolymer-grafted maleic anhydride (SEBS-g-MA), to reduce the interfacial tension between the two blend components. In the initial step, we prepared a 10% masterbatch of HDPE/TPEE with and without the compatibilizer using a twin-screw extruder. Subsequently, we processed the 10% masterbatch further through spun bonding to create fiber-in-fiber composites. Scanning electron microscopy (SEM) analysis revealed a significant reduction in the spherical size of HDPE/TPEE particles following the inclusion of SEBS-g-MA, as well as a much smaller TPEE nanofiber size (approximately 60-70 nm for 5% TPEE). Moreover, extensional rheological testing revealed a notable enhancement in extensional rheological properties, with strain-hardening behavior being more pronounced in the compatibilized nanofibrillar composites compared to the noncompatibilized ones. SEM images of the foam structures depicted substantial improvement in the foamability of HDPE in terms of the cell size and density following the nanofibrillation process and the use of the compatibilizer. Ultimately, the in situ rubber fibrillation and enhancement of HDPE and TPEE interface using a compatibilizer led to increasing the HDPE ductility at room and subzero temperatures while maintaining its stiffness.

Rheology of plant protein–polysaccharide gel inks for 3D food printing: Modeling and structure–property relations

Plant protein–polysaccharide composite hydrogels and emulsion gels are attractive materials for production of edible inks for 3D food printing. Their ability to satisfy the printability requirements is conventionally evaluated in small- and large-amplitude oscillatory shear tests. A model is derived that describes experimental data in linear and nonlinear rheological tests on protein gels in a unified manner. The model is based on the population-balance approach and involves a reasonably small number of adjustable parameters. Fitting observations on soy protein isolate–xanthan gum, peanut protein–gellan gum, peanut protein–carrageenan, pea protein–carrageenan and pea protein isolate–flaxseed gum gels demonstrates that material parameters evolve consistently with composition of the gels. The governing equations describe adequately the effects of pH and ionic strength of aqueous solutions on the mechanical properties of the gels and predict the stress–strain Lissajous curves and the crossover amplitudes for transition from the solid-like to fluid-like response. Based on the analysis of observations in large-amplitude oscillatory tests with various frequencies, a mechanism is proposed for transition from the type-I (strain thinning) to type-III (weak strain overshoot) response of protein–polysaccharide gels.

The impact of boron carbide in soft and hard body armor: A comprehensive evaluation on Kevlar and UHMWPE fabrics

AbstractIn this research, an investigation was conducted to ascertain the impact of boron carbide (B4C) microparticles on soft and hard armor configurations, utilizing two distinct high‐performance fabrics namely, Kevlar and Ultra‐high Molecular Weight Polyethylene (UHMWPE), also this work discerned the optimal fabric for protection against dagger attacks and 9 mm full metal jacket (FMJ) projectiles. Initially, rheological tests on four shear thickening fluid (STF) samples revealed that 70% of nano‐silicate (SiO2) content was the optimal ratio. Besides, scanning electronic microscope (SEM) tests showed that B4C affected the nano‐silicate dispersion. Hence, the use of STF as a matrix, led to complete protection in low‐velocity stab test and behavior improvement when subjected to NIJ ballistic test for both fabric types. On the other hand, the dynamic mechanical analysis (DMA) of the thermosetting epoxy resin‐based composites reinforced by B4C indicated that the 10% ratio offered maximum rigidity, resulting in improved ballistic performance. This study revealed that Kevlar fabrics exhibit superior behavior in soft protection, while UHMWPE hard composite display further rigidity against high‐velocity impacts. Overall, this work contributes novel insights into the efficiency of B4C integration within soft and hard armor configurations using two ballistic fabrics, highlighting their performance characteristics in ballistic shielding.Highlights Investigation of B4C microparticles: The research examines the impact of B4C microparticles on soft and hard armor configurations. High‐performance fabrics: Kevlar and UHMWPE uses. The use of STF as a matrix for soft and thermosetting epoxy resin for hard armor: enhanced composite performance. Low‐velocity and high‐velocity impact tests investigations; microparticles B4C incorporation: superior mechanical characteristics. Remarkable energy absorption: promising shielding uses.

Magnetic smart polymer gel with directional plugging for conformance control in oil reservoirs

Polymer gel technology has been proven to be one of the most effective methods for conformance control and enhanced oil recovery. However, to effectively gel highly permeable layers, precise placement of the gelant within the formation is required. Herein, to make the most use of polymer gel in conformance control, a novel magnetic smart polymer gel consisting of polyacrylamide and Fe3O4@polyethylenimine, is designed and prepared as a conformance fluid to achieve directional plugging in target reservoirs. To deeper understanding of the properties of Fe3O4@polyethylenimine and smart gel, as well as how they are formed and function, the microstructure of these materials was characterized through various techniques, including analysis of their crystal and chemical structures, micromorphology, and cross-linking mechanism, et al. The rheological tests suggest that the system has good viscosity and elasticity, and the gel strength can reach 105,463 mPa⋅s after aging 30 days at 120 °C. Furthermore, the controlled manipulation indicated that smart gel can move quickly and repeatedly to a designated location under a magnetic field. Additionally, the influence of the magnetic generator on the intelligent plugging performance of the smart gel system is also explored. It has been found that magnetic plugging can extend the effective lifespan of smart gel. Finally, the conformance control performance of the smart gel system is revealed by the parallel cores flow experiment. This work presents a novel smart gel system designed for directional plugging, to enhance conformance control in high-temperature oil reservoirs.

Development of interpenetrating network hydrogels: Enhancing the release and bioaccessibility of green tea polyphenols

Green Tea polyphenols (GTP) are important bioactive compounds with excellent physiological regulation functions. However, they are easily destroyed by the gastric environment during digestion. In this work, a sodium alginate (SA)-gellan gum (GG) interpenetrating network (IPN) hydrogel was synthesized to protect and delivery GTP. The ratio of SA/GG significantly affects the network structure of IPN hydrogels and the performance of delivering GTP. The hydrogel formed by interpenetrating 20 % GG with 80 % SA as the main network had the highest water uptake (55 g/g), holding capacity (950 mg/g), and freeze-thaw stability, with springiness reaching 0.933 and hardness reaching 1300 g, which due to the filling effect and non-covalent interaction. Rheological tests showed that the crosslink density of IPN hydrogel in SA-dominated network was improved by the addition of GG to make it better bound to GTP, and the higher water uptake meant that the system could absorb more GTP-containing solution. This IPN hydrogel maintained 917.3 mg/g encapsulation efficiency at the highest loading capacity (1080 mg/g) in tests as delivery system. In in vitro digestion simulations, owing to the pH responsiveness, the IPN hydrogel reduced the loss of GTP in gastric fluid, achieving a bioaccessibility of 71.6 % in the intestinal tract.

Influence of Carboxymethyl Cellulose as a Thickening Agent for Glauber's Salt-Based Low Temperature PCM.

This work is focused on a novel, promising low temperature phase change material (PCM), based on the eutectic Glauber's salt composition. To allow phase transition within the refrigeration range of temperatures of +5 °C to +12 °C, combined with a high repeatability of melting-freezing processes, and minimized subcooling, the application of three variants of sodium carboxymethyl cellulose (Na-CMC) with distinct molecular weights (700,000, 250,000, and 90,000) is considered. The primary objective is to optimize the stabilization of this eutectic PCM formulation, while maintaining the desired enthalpy level. Preparation methods are refined to ensure repeatability in mixing components, thereby optimizing performance and stability. Additionally, the influence of Na-CMC molecular weight on stabilization is examined through differential scanning calorimetry (DSC), T-history, and rheology tests. The PCM formulation of interest builds upon prior research in which borax, ammonium chloride, and potassium chloride were used as additives to sodium sulfate decahydrate (Glauber's salt), prioritizing environmentally responsible materials. The results reveal that CMC with molecular weights of 250 kg/mol and 90 kg/mol effectively stabilize the PCM without phase separation issues, slowing crystallization kinetics. Conversely, CMC of 700 kg/mol proved ineffective due to the disruption of gel formation at its low gel point, hindering higher concentrations. Calculations of ionic concentration indicate higher Na ion content in PCM stabilized with 90 kg/mol CMC, suggesting increased ionic interactions and gel strength. A tradeoff is discovered between the faster crystallization in lower molecular weight CMC and the higher concentration required, which increases the amount of inert material that does not participate in the phase transition. After thermal cycling, the best formulation had a latent heat of 130 J/g with no supercooling, demonstrating excellent performance. This work advances PCM's reliability as a thermal energy storage solution for diverse applications and highlights the complex relationship between Na-CMC molecular weight and PCM stabilization.

Tannic acid strengthen adhesion of poly(AAm-co-GG) hydrogels for multiple solid surfaces repairing

This study aims to develop bio-compatible mechanically robust, adhesive hydrogels using acrylamide and gellan gum. Tannic acid (TA) and N, N-methylene bisacrylamide (MBA) were used as physical and chemical crosslinkers respectively. Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) analysis verified the successful synthesis of hydrogels through free radical addition polymerization. The rheological tests, such as frequency sweep, creep recovery, and amplitude sweep were performed to evaluate the effect of TA on the adhesive behavior and viscoelastic properties of hydrogels. Results highlighted the pivotal role of polymer chain interactions in regulating the adhesive behavior. The tannic acid concentration was varied to assess the adhesive performance, higher tannic acid concentration resulted in improved adherence. The adhesion strength order was received as 33.6 > 18 > 7.56 > 6.7 > 6.23 kPa. The prepared adhesive hydrogels performed exceptionally well on wood, cloth, rubber, glass, and ceramics-like materials. Furthermore, the hydrogels were practically found efficient at low as well as at high temperatures. The low price, high efficiency, easy to synthesize, and bio-friendly. etc. characteristics can make these hydrogels to be applied convincingly as adhesives in the future.

Protein of yak milk residue: Structure, functionality, and the effects on the quality of non-fat yogurt

The purpose of this study was to compare the structural and functional of protein from yak milk residue, which collected from different elevations (MRP1 and MRP2) in Tibet, as well as their potential for enhancing the quality of non-fat yogurt. The results showed that MRP1 exhibited higher levels of β-sheet, turbidity, particle size, and gel properties. MRP2 had better flexibility, emulsification, foaming, water/oil absorption capacity. The addition of MRP1 (3%) could improve texture and sensory properties of yogurt. Although MRP2 yogurt had higher hardness, gumminess, chewiness and water holding capacity, poor mouthfeel. Rheological test showed that MRPs yogurt exhibited typical gel-like and shear-thinning behavior. Moreover, the fortification of non-fat yogurts with MRP1 brought the formation of larger protein clusters with a more tightly knit network of smaller pores. These results indicate that MRP1 can be used as a fat substitute to improve the quality of non-fat yogurt.

Lipid functionalization of magnesium oxide nanoparticles: Synthesis and characterization

In this study, magnesium oxide nanoparticles were synthesized and subsequently functionalized with phosphatidylcholine to potentially enhance their antimicrobial effects. The magnesium oxide nanoparticles exhibited a spherical shape with an average size of 102.6 ± 23.34 nm, while the functionalized ones measured 117.0 ± 27.79 nm. Functionalization was confirmed through characterization techniques such as ELS, SEM, FTIR, XRD, fluorescence analysis, TGA, Raman spectroscopy, and rheological tests, providing evidence of lipid functionalization and presenting physicochemical and technological characteristics that could potentially be utilized in a new antimicrobial nanosystem.

A chemical interpretation for the post-reversion upturn in the natural rubber/accelerated sulfur system based on the viscoelastic properties and cross-link density measurements

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.