High Viscoelasticity Research Articles

Self‐assembly properties of ultra‐long‐chain gemini surfactant with high performance in a fracturing fluid application

ABSTRACTA new cationic gemini surfactant (C25‐6‐C25), which had a special structure consisting of ultra‐long hydrophobic chains and amide groups, was synthesized using a main feedstock source obtained from rapeseed for thickening purposes. The 12 mmol L−1 C25‐6‐C25 fluid containing 0.19 mol L−1 potassium chloride (KCl) exhibited highly elastic properties at the angular frequency of 0.04–10 rad s−1. Its viscosity could be maintained at 55 mPa s for 1.5 h under a shear rate of 170 s−1 at 110 °C and it also showed a good proppant‐suspending property. C25‐6‐C25/KCl fluid exhibited high viscoelasticity and good performance, which were attributed to intermolecular forces, hydrogen bonding, and the shielding effect of electrostatic repulsion by KCl. Thus, C25‐6‐C25 is a very promising candidate for fracturing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44602.

Viscoelastic effect and creep elimination of dielectric elastomers in adversarial resonance

Dielectric elastomers are known to exhibit viscoelastic properties. When they are used in an adversarial resonator structure (known as a DEAR), the performance obtained is time-dependent. A thermodynamic model, involving the rheological model, is established to investigate the effect of viscoelasticity on the dynamic response. We verified the validity of our model by comparing with the experimental results. Based on the model, we theoretically analyze how the viscoelasticity is affected by the peak voltage, frequency, pre-stretching, temperature, and the shape of the signal waveform. The equilibrium position of the deformed membrane is found to drift severely during vibration, which can be attributed to the high viscoelasticity of the membrane. This behavior can lead to issues when designing precise instruments, and the drift of the equilibrium position can also result in the expansion of the amplitude envelope. We further demonstrate that under certain alternating electric loads, the viscoelastic drift of the equilibrium position is identical to the slow viscoelastic creep observed when the corresponding effective DC voltage is applied. Based on these findings and the adversarial mechanism of the DEAR structure, two strategies based on DC and AC offset correction are proposed to eliminate the viscoelastic drift. Simulation results show that applying AC offset correction has the additional benefit of allowing the amplitude of vibration to be continuously tunable over a specific range.

Light and electron microscopic analyses of the high deformability of adhesive toe pads in White's tree frog, Litoria caerulea.

White's tree frog (Litoria caerulea) has large, adhesive toe pads that are among the softest of all known biological structures. To explore the morphological basis for the physical properties of the toe pads, the internal microstructure of the toe pads in L. caerulea was examined using both light and transmission electron microscopy. Three design elements that are distinct from other areas of skin were observed. First, the keratinocytes comprising the adhesive surface of the toe pad all contained keratin filament bundles (tonofibrils) exhibiting structural anisotropy. Specifically, the curved conformation of the hierarchical (branching) tonofibrils was characterized by the formation of anastomoses consisting of tonofibrils beneath the adhesive cell surface and stem keratin filament bundles concentrated in the lower-middle part of the dorsal-side of adhesive cells. Second, the cytoplasm of keratinocytes in the most superficial cell layer contained glycoproteins (stained by periodic acid/Schiff reagent) that are considered to confer high viscoelasticity. Third, the dermis contained large lymph spaces interspersed with elastic fibers and collagen fibers, which were relatively sparsely distributed compared to the dorsal skin of the toe pads. The profiles of these structures were easily deformed by the slight application of pressure. These findings reaffirmed that the unique internal architecture of the toe pads in L. caerulea contributed to their remarkable softness and high deformability, which in turn increased the contact area and provided improved adaptability to the local topography of natural surfaces. J. Morphol. 277:1509-1516, 2016. © 2016 Wiley Periodicals, Inc.

Supramolecular Fluid of Associative Polymer and Viscoelastic Surfactant for Hydraulic Fracturing

Summary This paper details the study of a new fracturing fluid that is based on a supramolecular complex between associative polymer and viscoelastic surfactant (VES). The crosslinked complex gel was based on weak physical attractive forces, such as van der Waals, hydrogen bonding, and electrostatic interaction between associative polymer and wormlike micelles of VES. The concentration of surfactant in the new fluid is 10 times less than that of VES fracturing fluid. The combination of VES and associative polymer synergistically enhances the viscosity to several times more than that of the individual components alone. The fluid system was optimized by experimental design. The microstructure of wormlike micelles and complex formation was verified by electron microscopy. The fluid is shear stable at high temperature for 1 hour. The dynamic rheological properties of the supramoleulcar fluid show high viscoelasticity, in which the elastic moduli are higher than the loss moduli below an angular frequency of 0.1 rad/s. The proppant-transport test in a large-scale fracture simulator showed good proppant-suspension ability. The fluid has 50% lower formation damage than conventional guar. The fluid was prepared with fewer additives, formed gel instantly, and can be mixed on the fly in the field. The gel can be completely broken with almost no residue. Field application of the new fracturing fluid in a gas well showed the enhancement of gas production by more than 100%. The fluid has 20% lower friction pressure than guar fluid. Hence, the new supramolecular fluid is an effective fracturing fluid.

Dual-Responsive Viscoelastic Lyotropic Liquid Crystal Fluids to Control the Diffusion of Hydrophilic and Hydrophobic Molecules.

A smart lyotropic liquid crystal (LLC) system was prepared to control the diffusion rate of hydrophilic and hydrophobic molecules. The LLC system is composed of a nonionic surfactant (tetraethylene glycol monododecylether; C12 EO4 ) and an anionic azobenzene surfactant (Azo-surfactant). C12 EO4 was the main component of the LLC system. The Azo-surfactant, which can undergo photo-isomerization, played the role of trigger in this system. LLC gels formed in a solution comprised of Azo-surfactant (10 mm) and C12 EO4 (300 mm). The LLC gels became broken when more Azo-surfactant was added (e.g., up to 15 mm) and the viscoelasticity was lost. Surprisingly, when we used UV light to irradiate the 300 mm C12 EO4 /15 mm Azo-surfactant sample, the gel was recovered and high viscoelasticity was observed. However, under visible-light irradiation, the gel became broken again. The gel formation could also be triggered by heating the sample. On heating the 300 mm C12 EO4 /15 mm Azo-surfactant sample, the system thickened to a point at which typical gel behavior was registered. When the sample was cooled, the gel broke again. The LLC could be used for controlled release of hydrophilic and hydrophobic molecules, and could be considered as a versatile vehicle for the delivery of actives in systems of practical importance.

Replication of skilled polishing technique with serial–parallel mechanism polishing machine

Currently, viscoelastic polymers are used to coat automotive body to prevent scratches. On the other hand, the application of a polymer with high viscoelasticity makes the repair polishing process of the coated body more difficult. Hence, performing the polishing process requires the operator to be technically skilled. However, the number of workers with necessary technical skill has been decreasing because of an aging population. In addition, the surface quality and process time are dependent on the proficiency level of the worker. To automate the repair polishing process, in our past research, a serial–parallel mechanism polishing machine was developed to simultaneously control the tool trajectory, tool posture, and polishing force. The present study aims to construct a replication system of a skilled polishing technique on the basis of the above three physical parameters by applying the developed polishing machine. First, the tool trajectory, tool posture, and polishing force of a skilled worker, which reflect the polishing technique, were acquired using a high-speed camera and a dynamometer. By inputting the acquired data to the developed machine, the machine can copy the polishing technique because the tool trajectory, tool posture, and polishing force can be independently controlled. From the results of the polishing test, the surface quality after polishing was comparable to that of the skilled worker output, which satisfies the criteria of surface quality.

Biotechnological production of hyaluronic acid: a mini review.

Hyaluronic acid (HA) is a polysaccharide found in the extracellular matrix of vertebrate epithelial, neural and connective tissues. Due to the high moisture retention, biocompatibility and viscoelasticity properties of this polymer, HA has become an important component of major pharmaceutical, biomedical and cosmetic products with high commercial value worldwide. Currently, large scale production of HA involves extraction from animal tissues as well as the use of bacterial expression systems in Streptococci. However, due to concerns over safety, alternative sources of HA have been pursued which include the use of endotoxin-free microorganisms such as Bacilli and Escherichia coli. In this review, we explore current knowledge of biosynthetic enzymes that produce HA, how these systems have been used commercially to produce HA and how the challenges of producing HA cheaply and safely are being addressed.

Foamability of sodium dodecyl sulfate solutions: Anomalous effect of dodecanol unexplained by conventional theories

Conventional theories indicate that surfactant solutions with low surface tension, fast adsorption kinetics, and high interfacial viscoelasticity increase foamability. These theories are applicable to single surfactants of pre-CMC. Here, we examine whether these theories are applicable for surfactant mixtures. Specifically, we investigated the foamability of sodium dodecyl sulfate (SDS)-dodecanol (DOH) solutions. We found that the foamability of SDS–DOH solutions exhibited ‘anomalies’ that were unexplained by conventional theories. The remarkable decrease in the foamability of SDS solutions caused by the addition of DOH could not be easily explained by the theories of surface tension and surface viscoelasticity. Instead, we proposed alternative mechanisms to resolve these unexpected results. Below the DOH solubility limit, the replacement of SDS molecules by DOH molecules at the air–water interface results in a reduced surface potential, leading to a lower foamability. The antifoam effects of DOH droplets can account for the reduced foamability above this limit. This paper highlights the complex effect of surfactant mixtures on foamability.

Stretching-induced ion complexation in physical polyampholyte hydrogels.

Recently, we have developed a series of charge balanced polyampholyte (PA) physical hydrogels by random copolymerization in water, which show extraordinarily high toughness, self-healing ability and viscoelasticity. The excellent performance of PA hydrogels is ascribed to dynamic ionic bond formation through inter- and intra-chain interactions. The randomness results in ionic bonds of wide strength distribution, the strong bonds, which serve as permanent crosslinking, imparting the elasticity, while the weak bonds reversibly break and re-form, dissipating energy. In this work, we developed a simple physical method, called a pre-stretching method, to promote the performance of PA hydrogels. By imposing a pre-stretching on the sample in the as-prepared state, ion complexation during dialysis is prominently accelerated and the final performance is largely promoted. Further analysis suggests that the strong bond formation induced by pre-stretching is responsible for the change in final performance. Pre-stretching decreases the entropy of the system and increases the chain alignment, resulting in an increased possibility for strong bond formation.

Rheology and Rheokinetics of Photosensitive Micelle Composed of 3-Chloro-2-Hydroxypropyl Oleyl Dimethyl Ammonium Acetate and trans-4-Phenylazo Benzoic Acid

A novel rheological reversible photosensitive micelle composed of 3-chloro-2-hydroxypropyl oleyl dimethyl ammonium acetate (ODAA) and trans-4-phenylazo benzoic acid (trans-ACA) was investigated. The mixed micelle system under a suitable molar ratio (ODAA:ACA = 1.25:1) shows great viscoelastic property. Before UV irradiation, the ODAA/ACA micelle system exhibits high viscosity and good viscoelasticity. Upon irradiation by UV light (365 nm), ACA undergoes a photoisomerization from its trans to its cis form, causing a change of the molecular structure, which leads to viscosity decreases obviously; thixotropy and viscoelasticity almost disappear. The above changes of rheological properties can be reversible by exposing to visible light. Furthermore, the rheokinetics process of ODAA/ACA micelle system during UV irradiation was studied and rheokinetics equation was established, which can well describe the changing processes of viscosity and viscoelasticity. The viscoelasticity process is divided into two sections to be simulated by rheokinetics equation. In addition, these photosensitive phenomena are repeatable easily and the mechanism can be validated by UV-vis spectra.

The influence of printing parameters on cell survival rate and printability in microextrusion-based 3D cell printing technology

Three-dimensional (3D) cell printing technology has provided a versatile methodology to fabricate cell-laden tissue-like constructs and in vitro tissue/pathological models for tissue engineering, drug testing and screening applications. However, it still remains a challenge to print bioinks with high viscoelasticity to achieve long-term stable structure and maintain high cell survival rate after printing at the same time. In this study, we systematically investigated the influence of 3D cell printing parameters, i.e. composition and concentration of bioink, holding temperature and holding time, on the printability and cell survival rate in microextrusion-based 3D cell printing technology. Rheological measurements were utilized to characterize the viscoelasticity of gelatin-based bioinks. Results demonstrated that the bioink viscoelasticity was increased when increasing the bioink concentration, increasing holding time and decreasing holding temperature below gelation temperature. The decline of cell survival rate after 3D cell printing process was observed when increasing the viscoelasticity of the gelatin-based bioinks. However, different process parameter combinations would result in the similar rheological characteristics and thus showed similar cell survival rate after 3D bioprinting process. On the other hand, bioink viscoelasticity should also reach a certain point to ensure good printability and shape fidelity. At last, we proposed a protocol for 3D bioprinting of temperature-sensitive gelatin-based hydrogel bioinks with both high cell survival rate and good printability. This research would be useful for biofabrication researchers to adjust the 3D bioprinting process parameters quickly and as a referable template for designing new bioinks.

A rheological investigation of sol–gel transition of hydroxypropyl cellulose with nonionic surfactant sorbitan monopalmitate: Modulation of gel strength by UV irradiation

Abstract The interaction of hydrophobically modified biocompatible polymer hydroxypropyl cellulose (HPC) with nonionic surfactant sorbitan monopalmitate (Span 40) in aqueous solutions have been studied using rheology. The associated physicochemical properties of the HPC+ Span 40 mixed system such as cac, psp and cmc were studied as a function of Span 40 concentration. Steady shear rheological experiments indicate that the HPC as well as HPC+ Span 40 systems possesses two distinct regions in the rheogram Newtonian followed by Pseudoplastic behavior, and behave as plastic systems with the value of m parameter in the empirical Cross model equation η 0 − η α / η − η α = 1 / 1 + C ( γ ) m varying between 0.725–0.675 and 2.24–1.58 in the first and second shear thinning regions. Dynamic rheological results suggest that the microstructural changes that occur during thermo reversible gelation of aqueous solutions of HPC and HPC+ Span 40 systems follow a two step mechanism i.e., gelation followed by precipitation. The thermal stability of the HPC hydrogel decreases as the concentration of Span 40 increases. Moreover, increase in the UV radiation dose on 10% HPC increases its gel strength probably due to the formation of active radicals in the polymer which on further reaction results in formation of highly cross linked gel of high viscoelasticity. However, this phenomena was not observed in 10% HPC solution after addition of Span 40.

Mechanical behavior and failure mechanism of recycled semi-flexible pavement material

The mechanical behavior and failure mechanism of recycled semi-flexible pavement material were investigated by different scales method. The macroscopic mechanical behavior of samples was studied by static and dynamic splitting tensile tests on mechanics testing system (MTS). The mechanical analysis in micro scale was carried out by material image analysis method and finite element analysis system. The strains of recycled semi-flexible pavement material on samples surface and in each phase materials were obtained. The test results reveal that the performance of recovered asphalt binder was the major determinant on the structural stability of recycled semi-flexible pavement material. The asphalt binder with high viscoelasticity could delay the initial cracking time and reduce the residual strain under cyclic loading conditions. The failure possibility order of each phase in recycled semi-flexible pavement material was asphalt binder, reclaimed aggregate, cement paste and virgin aggregate.

Ultrasound aided smooth dispensing for high viscoelastic epoxy in microelectronic packaging

Epoxy dispensing is one of the most critical processes in microelectronic packaging. However, due its high viscoelasticity, dispensing of epoxy is extremely difficult, and a lower viscoelasticity epoxy is desired to improve the process. In this paper, a novel method is proposed to achieve a lowered viscoelastic epoxy by using ultrasound. The viscoelasticity and molecular structures of the epoxies were compared and analyzed before and after experimentation. Different factors of the ultrasonic process, including power, processing time and ultrasonic energy, were studied in this study. It is found that elasticity is more sensitive to ultrasonic processing while viscosity is little affected. Further, large power and long processing time can minimize the viscoelasticity to ideal values. Due to the reduced loss modulus and storage modulus after ultrasonic processing, smooth dispensing is demonstrated for the processed epoxy. The subsequently color temperature experiments show that ultrasonic processing will not affect LED’s lighting. It is clear that the ultrasonic processing will have good potential to aide smooth dispensing for high viscoelastic epoxy in electronic industry.

PH-switchable wormlike micelle formation by N-alkyl-N-methylpyrrolidinium bromide-based cationic surfactant

A non-covalent bonding method is utilized for forming pH-switchable wormlike micelles system by mixing N-hexadecyl-N-methylpyrrolidinium bromide-based cationic surfactant and pyrocatechol. The peculiarity of this system is that it has high viscoelasticity at acidic conditions and alkaline conditions, while it shows water-like behaviors at neutral conditions. Rheology, dynamic light scattering, and cryogenic-transmission electron microscopy results revealed that the microstructure transition between spherical micelles and wormlike micelles was the fundamental cause of the pH-switchable rheological properties. The unusual rheological and micellar responses of this system to pH are caused by different binding capacity of hydrotrope to C16MPBr as pH varies. Fluorescence analysis and nuclear magnetic resonance result support this hypothesis.

Worm‐like micelles: A new approach for heavy oil recovery from fractured systems

In this work, a new type of flooding system, “worm‐like micelles”, in enhanced heavy oil recovery (EOR) has been introduced. Application of these types of surfactants, because of their intriguing and surprising behaviour, is attractive for EOR studies. Fundamental understanding of the sweep efficiencies as well as displacement mechanisms of this flooding system in heterogeneous systems especially for heavy oils remains a topic of debate in the literature. Worm‐like micellar surfactant solutions are made up of highly flexible cylindrical aggregates. Such micellar solutions display high surface activity and high viscoelasticity, making them attractive in practical applications for EOR. In this study, worm‐like micellar solutions were used for flooding experiments in micromodels, initially saturated with heavy crude oil. The fractured micromodels with different fracture geometrical properties, different orientation angles and length, were used in the tests under oil‐wet condition. During experiments, high quality pictures of injection processes were recorded. Oil recoveries as a function of injected pore volumes and microscopic mechanisms during displacements were investigated from precise analyses of the provided pictures. It was observed that three mechanisms govern the EOR process during worm‐like micellar solution flooding: ultra‐low interfacial tension, high viscosity of the injecting fluid and in situ formation of macro‐emulsion. Considering these mechanisms, worm‐like micellar surfactants solutions are potentially good choices for EOR in heterogeneous systems such as fractured reservoirs. This study illustrates that the application of worm‐like micelles for heavy oil recovery in heterogeneous systems can reduce the risks involved with heterogeneity on flooding performance in such reservoirs.

A simulation study on the effect of spring-shaped fillers on the viscoelasticity of rubber nanocomposite

Background/PurposeRubber nanocomposites have been widely used in many engineering fields due to their unique properties such as high elasticity and viscoelasticity. Much attention has been paid to the viscoelasticity of rubbers because it directly relates to the performance of the rubber products. MethodsBased on the micromechanical theory, the finite element method is used to analyze the effect of elastic modulus and volume content of spring-shape nanofillers on the dynamic viscosity of composites. ResultsThe simulation results show that there is an optimal elastic modulus of spring-shape nanofillers to make the loss factor a minimum. There is a threshold value of spring-shape nanofiller content for the dissipation energy density of composite. ConclusionThe elastic modulus of spring-shape nanofillers has a large effect on the loss factor of composites. The selection of elastic modulus of spring-shape nanofillers is critical for applications of composites. The efficiency of spring-shape nanofillers in reducing the dynamic viscosity of composites is so high that volume content of spring-shape nanofillers as low as 0.1% can greatly reduce the loss factor of composites with bonding interface.

MoP-37 HIGH FREQUENCY VISCOELASTICITY FOR MEDIA HANDLING

Paper handling technology is based on a function of the friction. Reliability degradation is mainly occurred by the boundary lubrication state by the paper powder film on rubber roller surface. In this condition, friction is said to have a large influence of the hysteresis loss of the rubber viscoelasticity in the high frequency over megahertz vibration caused by the paper surface roughness. We have investigated the relationship between a high frequency viscoelasticity by the ultrasound measuring apparatus and a friction of rubber roller by the high speed roller slip rate tester.

Faceted fatty acid vesicles formed from single-tailed perfluorinated surfactants.

The aggregation behavior and rheological properties of two mixtures of perfluorononanoic acid (PFNA)/NaOH and perfluorodecanoic acid (PFDA)/NaOH were investigated in aqueous solutions. Interestingly, pH-sensitive polyhedral fatty acid vesicles were spontaneously formed in both systems, which were determined by freeze-fracture transmission electron microscopy (FF-TEM) measurements. Especially, a phase transition from faceted vesicles to the L3 phase with the increase of pH was observed in the PFNA/NaOH system while it was not observed in the PFDA/NaOH system. Differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) measurements confirmed that the bilayers of the faceted vesicles were in the crystalline station indicating that the crystallization of fluorocarbon chains was the main driving force for their formation. Besides, the two systems of faceted perfluorofatty acid vesicles exhibit interesting rheological properties, for instance, they showed high viscoelasticity and shear-thinning behaviour, and the elastic modulus (G') and viscous modulus (G'') of PFDA/NaOH vesicles were much higher than those of PFNA/NaOH vesicles. Conversely, the solution of the L3 phase with fluid bilayers did not present viscoelastic properties. Therefore, the viscoelastic properties of vesicles resulted from the crystalline fluorinated alkyl chains with high rigidity at room temperature and the dense packing of vesicles. As far as we know, such faceted fatty acid vesicles formed from single-tailed perfluorinated surfactants have been rarely reported. Our work successfully constructs polyhedral fatty acid vesicles and proposes their formation mechanism, which should be a great advance in the fundamental research of fatty acid vesicles.

Reversible thermal behaviour of vegetable oil cellulose ether emulsions as fat replacers. Influence of glycerol

Thermal reversibility properties of vegetable oil cellulose ether emulsions with and without glycerol incorporation were studied by small amplitude oscillatory shear, optical microscopy and particle size analysis. Differences in the viscoelastic properties were observed among the different cellulose emulsions at 20 °C and 80 °C after thermal gelation. At 20 °C the highest viscoelasticity was shown by the MX emulsion. The emulsion gelation temperature decreased with cellulose ether methoxyl content and with the presence of glycerol. Emulsion MX showed the lowest thermal stability. Heating the MX cellulose emulsion caused syneresis, fat flocculation and the appearance of particle size polydispersity, indicating lower thermal stability and lower thermal reversibility. The different viscoelastic properties and thermal stabilities obtained by varying the type of cellulose, both with and without glycerol incorporation, increase the number of possible food applications where the emulsions could be employed as suitable fat replacers. Whether higher or lower emulsion thermal stability is more or less convenient for a specific food application is a future topic of study.