Effect of pH on the rheological properties of borate crosslinked hydroxypropyl guar gum hydrogel and hydroxypropyl guar gum

Gums from different botanical sources: Physicochemical characterization seldom found in literature

Acidity, simple sugars, and minerals can impact gum properties, thus defining their applications. This study aimed to evaluate and compare rarely reported physicochemical properties of commercial gums from diverse botanical sources used as food additives. The gums studied, as they come from different plants, are believed to present differences in the characteristics evaluated. The content of minerals, simple sugars, pH, and titratable acidity was assessed in the arabic, locust bean, and guar gums. All gums contain trace amounts of simple sugars and minerals P, K, Ca, Mg, and S. Titratable acidity results found in gums may indicate the presence of organic acids. This work concludes that the gums studied are formed by polysaccharides and form slightly acid solutions.

Quantitative characterization of the crosslinking degree of hydroxypropyl guar gum fracturing fluid by low-field NMR

As a widely used water-based fracturing fluid, the performance of hydroxypropyl guar gum fracturing fluid is closely related to the degree of crosslinking, the quantitative characterization of which can reveal a detailed crosslinking mechanism and guide the preparation of fracturing fluid gels with an excellent performance. However, the commonly used high-temperature rheology method for evaluating the performance of fracturing fluids only qualitatively reflects the degree of crosslinking. In this study, low-field nuclear magnetic resonance (LF-NMR) was used to characterize the degree of crosslinking in guar gum fracturing fluid gels. The spin-spin relaxation time of the H proton in guar gum was molecularly analyzed using LF-NMR. The viscoelastic properties met the requirements when the crosslinking degree of the gel was 88-94 %. The transformation of the linear structure into a membrane structure during the crosslinking process of the guar gum fracturing fluid was confirmed by freeze-drying and scanning electron microscopy (SEM) from a microscopic perspective. The changing trend of the microstructure and viscoelastic properties of the fracturing fluid gel under different crosslinker dosages was consistent with changes in the degree of crosslinking. The LF-NMR test process is non-destructive to the gel structure, and the test results demonstrate good accuracy and repeatability.

Steady and dynamic shear rheology of aqueous solutions of quince seed gum combinations with locust bean or xanthan gums

This study presents the rheological properties of quince seed gum (Q) solution in comparison with xanthan gum (X) and locust bean gums (L) and the polymeric interactions of different ratios of Q:X and Q:L blends (1:1, 1:3 and 3:1). Q exhibits greater and stronger elastic properties than X and L. The frequency and temperature stability of Q and X are both higher than that of L. The viscoelastic properties of Q:X and Q:L solutions were found to be higher than those of the individual solutions. The higher polymer entanglements observed in Q:L blends resulted in enhanced synergistic interactions and thixotropy compared to Q:X. 3QX exhibited an enhanced elastic structure, but the best synergism was observed for 3QL due to the establishment of a stronger intermolecular bond for gelling. The lower tan δ observed with increasing Q indicate a Q-induced synergistic interaction with L. At all temperatures, 3QL showed the highest thixotropy. The combination of Q and L resulted in the formation of a true gel, with the higher gel strength being observed for QL and 3QL. This study shows that Q:L and Q:X combinations can yield desired flow properties. In particular, L provides a firmer gel network with Q.

Influence of 3-chloropropyl) triethoxysilane and pH on the properties of modified guar gum film

Guar gum (GG) as a polymer biopolymer is widely used in the field of bio-based packaging. However, its poor mechanical properties, barrier properties and high viscosity greatly hinder its use as an effective packaging material. Therefore, this study introduced CPTES to improve the mechanical (16.58-27.39 MPa) and tensile properties (26.80 %-30.67 %). The FTIR and XRD results indicated a strong interaction between the biofilm fractions modified by CPTES, CPTES bound to the hydroxyl groups on GG and formed a dense polysiloxane network through adsorption and grafting. OM and AFM reflect a denser and flatter film structure on the surface of the G30 film, which has the best film formation. Based on this, the pH of the solution was further adjusted to reach an alkaline environment, disrupting the intermolecular binding through electrostatic repulsion. The rheological behavior indicates that the viscosity and viscoelasticity of film solution gradually decrease with the increase in pH. OM and AFM results show that the G30/8 film has the best compact properties, while the nonporous compact film structure further improves the mechanical, barrierand and thermodynamic properties of the film. Accordingly, the findings of this study had a certain value for regulating the low viscoelasticity of GG emulsion and enhancing the stability of film formation.

Applications of inverse opal photonic crystal hydrogels in the preparation of acid-base color-changing materials

Hydrogels are three-dimensional (3D) crosslinked network hydrophilic polymers that have structures similar to that of biological protein tissue and can quickly absorb a large amount of water. Opal photonic crystals (OPCs) are a kind of photonic band gap material formed by the periodic arrangement of 3D media, and inverse opal photonic crystals (IOPCs) are their inverse structure. Inverse opal photonic crystal hydrogels (IOPCHs) can produce corresponding visual color responses to a change in acid or alkali in an external humid environment, which has wide applications in chemical sensing, anti-counterfeiting, medical detection, intelligent display, and other fields, and the field has developed rapidly in recent years. In this paper, the research progress on fast acid-base response IOPCHs (pH-IOPCHs) is comprehensively described from the perspective of material synthesis. The technical bottleneck of enhancing the performance of acid-base-responsive IOPCHs and the current practical application limitations are summarized, and the development prospects of acid-base-responsive IOPCHs are described. These comprehensive analyses are expected to provide new ideas for solving problems in the preparation and application of pH-IOPCHs.

Experimental Investigation of Hydraulic Fracturing Fluid Based on Pseudo Gemini Surfactant with Polysaccharide Addition

In the last decade, hydrogels for hydraulic fracturing based on viscoelastic surfactants have been actively studied. Interest in these systems is justified by their unique qualities: good viscoelasticity and the ability to form stable suspensions of proppant or sand, destruction without the formation of bridging agents, hydrophobization of the rock surface and metal of technological equipment, as well as oil-cleaning properties. These qualities are most often provided by a minimum set of components-a surfactant and an electrolyte. However, the absence of a polymer limits the use of these gels in formations where fluid leakoff is possible. In this article, a liquid was studied, based on a pseudo gemini surfactant (PGVES) with the addition of a water-soluble polysaccharide. The objects of study were selected based on the assumption of interactions between PGVES and the polymer; interactions which favorably influence the technological characteristics of the fracturing fluid. To confirm the hypothesis, rheological studies were carried out. These included rotational viscometry and oscillatory studies at various temperatures. The settling velocity of particles of various proppant fractions was studied and tests were carried out to assess fluid leakoff. The performed experiments show an improvement in the characteristics of the PGVES-based gel under the influence of the polysaccharide. In particular, the rheological properties increase significantly, the stability of proppant suspensions improves, and the fluid leakoff of systems decreases, all of which expands the possibility of using these fracturing fluids and makes this area of experimentation promising.

Double Photocrosslinked Responsive Hydrogels Based on Hydroxypropyl Guar

Double crosslinked hydrogels based on a biodegradable polymer were prepared by photocopolymerization of methacrylated hydroxypropyl guar (HPG-MA) and 3-acrylamidophenylboronic acid. Along with irreversible strong covalent crosslinks by methacrylic groups, these hydrogels contained labile boronate crosslinks formed as a result of the interaction of boronic acid with cis-diol moieties of HPG. These hydrogels demonstrated higher elasticity than HPG-MA hydrogels with only irreversible covalent crosslinks. Labile boronate crosslinks not only strengthened the hydrogels but also imparted to them pronounced responsive properties. It was demonstrated that the mechanical properties, the swelling behavior, as well as the uptake and release of some substances from the double crosslinked hydrogel were pH controlled. For instance, the hydrogels could release cationic disinfectant at a rate regulated by pH. Such photocrosslinkable in situ forming hydrogels are very promising for the production of smart coatings that release targeted substances at the desired rate.

Novel ultra-stretchable and self-healing crosslinked poly (ethylene oxide)-cationic guar gum hydrogel

Hydrogels are three-dimensional structures with specific features that render them useful for biomedical applications, such as tissue engineering scaffolds, drug delivery systems, and wound dressings. In recent years, there has been a significant increase in the search for improved mechanical properties of hydrogels derived from natural products to extend their applications in various fields, and there are different methods to obtain strengthened hydrogels. Cationic guar gum has physicochemical properties that allow it to interact with other polymers and generate hydrogels. This study aimed to develop an ultra-stretchable and self-healing hydrogel, evaluating the influence of adding PolyOX [poly(ethylene oxide)] on the mechanical properties and the interaction with cationic guar gum for potential tissue engineering applications. We found that variations in PolyOX concentrations and pH changes influenced the mechanical properties of cationic guar gum hydrogels. After optimization experiments, we obtained a novel hydrogel, which was semi-crystalline, highly stretchable, and with an extensibility area of approximately 400 cm2, representing a 33-fold increase compared to the hydrogel before being extended. Moreover, the hydrogel presented a recovery of 96.8% after the self-healing process and a viscosity of 153,347 ± 4,662 cP. Therefore, this novel hydrogel exhibited optimal mechanical and chemical properties and could be suitable for a broad range of applications in different fields, such as tissue engineering, drug delivery, or food storage.

Application of Hydrogels and Hydrocarbon-Based Gels in Oil Production Processes and Well Drilling

The use of gels in oil production processes has become a regular practice in oilfield operations and is constantly developing in all oil-producing countries of the world, as evidenced by the growth of publications and patent activity on this topic. Many oil production processes, such as hydraulic fracturing, conformance control, water, and gas shutoff, cannot be imagined without the use of gel technologies. Inorganic, organic, and hybrid gels are used, as well as foams, gel-forming, and gel-dispersed systems. The possibility of a broad control of structural and mechanical properties, thermal stability, and shear resistance by introducing microscale and nanoscale additives made hydrogels and hydrocarbon-based gels indispensable tools for oil engineers.

Study of crosslinker size on the rheological properties of borate crosslinked guar gum

Borate crosslinked guar gum gels have played a vital role in stimulating oil and gas wells for many years; however, the high dosage of guar gum in the existing fracturing fluid will increase the cost and cause more damage to the reservoir and ultimately affect the effect of stimulation. In this study, borate esters are modified onto polyethyleneimine (PEI) of different molecular weights, affording organic borate crosslinkers of different sizes. By analyzing the effect of crosslinker size on gel rheology, sand-carrying properties, and microstructure, it is observed that the crosslinking efficiency is most significantly enhanced when the crosslinker size is similar to the diameter of the guar gum molecules. This makes it possible for the gel to maintain good performance at low polymer concentrations and meet the performance requirements of fracturing, which provides new ideas for developing the next generation of economical, clean, and green fracturing fluids.

pH responsive cationic guar gum-borate self-healing hydrogels for muco-adhesion

We developed a new muco-adhesive hydrogel composed of cationic guar gum (CGG) and boric acid (BA). The CGG-BA precursor solution of 0.5-2% w/v concentration exhibited fluidity at low pH (3-5), while gelation occurred within 1 min at physiological pH (7-8) conditions. Scanning electron microscopy and Fourier-transform infrared spectroscopy results confirmed the change in physical and chemical behavior, respectively, with change in pH. The pH-responsive self-healing ability was analyzed through microscopy and rheology. CGG-BA hydrogels showed good self-healing property at pH 7.4. The in vitro biocompatibility test of the hydrogel studied using NIH3T3 and NHEK cells showed that it was non-toxic at concentrations of CGG-BA below 2% w/v. Ex vivo mucoadhesive tests confirmed the hydrogel's potential for use as a muco-adhesive. Burst pressure tests were conducted using pig esophageal mucosa and the results showed that at pH 7.4, 1% w/v CGG-BA self-healable hydrogel resisted about 8 ± 2 kPa pressure, comparable to that of Fibrin glue. This was higher than that at solution (pH 5) and brittle gel (pH 10) conditions. To confirm the good adhesive strength of the self-healable hydrogels, lap shear tests conducted, resulted in adhesive strengths measured in the range of 1.0 ± 0.5-2.0 ± 0.6 kPa, which was also comparable to fibrin glue control 1.8 ± 0.6 kPa. Hydrogel weight measurements showed that 40-80% gel lasted under physiological conditions for 10 h. The results suggest that CGG-BA hydrogel has potential as a pH responsive mucosal protectant biomaterial.

Effect of soy protein isolate on physical properties of quinoa dough and gluten-free bread quality characteristics

BACKGROUND

Quinoa is a good gluten-free resource for food processing, especially bread making, and can improve and prevent the development of complications associated with celiac disease (CD). However, lack of gluten affects quinoa bread quality. Previous research showed that soy protein isolate (SPI) could improve gluten-free bread quality to some extent. Therefore, this study investigated the effects of SPI on the physical properties of quinoa dough and gluten-free bread quality characteristics.

RESULTS

Results showed that, with appropriate SPI substitution, the farinograph properties of quinoa flour significantly improved (P < 0.05). The sample with 8% SPI substitution showed a better development time (DT, 3.30 ± 0.20 min), stability time (ST, 8.80 ± 0.10 min) and softening degree (SD, 8.80 ± 0.10 FU), which were close to those of wheat flour, although more water absorption (WA, 76.40 ± 2.10%) was needed than for wheat flour (66.30 ± 3.10%). The extensograph properties of quinoa flour also significantly improved after 8% SPI substitution (P < 0.05). Furthermore, SPI substitution increased G' moduli of quinoa dough and decreased tan δ to some extent, providing better rheological properties closer to those of wheat dough. SPI substitution also improved the quality and texture of quinoa bread and reduced the gap with wheat bread. When SPI substitution was 8%, the specific volume, hardness and springiness of quinoa bread were 2.29 ± 0.05 mL g^-1 , 1496.47 ± 85.21 g and 0.71 ± 0.03%, respectively.

CONCLUSION

These results suggested that SPI substitution would be an effective way to develop higher-quality gluten-free bread. © 2022 Society of Chemical Industry.

Experimental investigation on the high-pressure sand suspension and adsorption capacity of guar gum fracturing fluid in low-permeability shale reservoirs: factor analysis and mechanism disclosure

Guar fracturing technology has been considered as a kind of popular EOR technology, but the weak static suspension capacity becomes a challenge due to the poor temperature resistance and stability of guar fracturing fluid. The main goal of this investigation is to explore the effect of different factors on the high-pressure static sand suspension of guar gum fracturing fluid by a synthetic efficient nano-ZrO₂ cross-linker. In particular, a mechanism of static suspended sand of nano-ZrO₂ cross-linker is analyzed by microscopic simulation. The adsorption performance of guar fracturing fluid on the shale surface is also studied for analyzing the environmental pollution and damage of guar gum fracturing fluid to shale reservoirs after cross-linking in this investigation. The results obtained that the inclusion of a small content of nano-ZrO₂ cross-linker (0.4%) leads to an apparent increase of fracturing fluid viscosity and decrease in the falling quality of gravel (104 mPa·s and 0.3 g) compared to the classical cross-linker (63 mPa·s and 3.5 g). The lower adsorption capacity of guar fracturing fluid containing nano-ZrO₂ cross-linker on the shale surface means that it has a weaker pollution ability to the shale reservoir than the commercially available cross-linker. Meanwhile, the grid structure density formed by nano-cross-linker and guar gum is considered to be the key factor to significantly change the suspended sand capacity. The investigation of nano-cross-linker cannot only provide necessary theoretical technology and data support for the stability of water-based fracturing fluid, efficient sand carrying, and the development of water-based fracturing technology, but also effectively protect the underground shale reservoir.

Crosslinkers for polysaccharides and proteins: Synthesis conditions, mechanisms, and crosslinking efficiency, a review

Polysaccharides and proteins are important macromolecules for developing hydrogels devoted to biomedical applications. Chemical hydrogels offer chemical, mechanical, and dimensional stability than physical hydrogels due to the chemical bonds among the chains mediated by crosslinkers. There are many crosslinkers to synthesize polysaccharides and proteins based on hydrogels. In this review, we revisited the crosslinking reaction mechanisms between synthetic or natural crosslinkers and polysaccharides or proteins. The selected synthetic crosslinkers were glutaraldehyde, carbodiimide, boric acid, sodium trimetaphosphate, N,N'-methylene bisacrylamide, and polycarboxylic acid, whereas the selected natural crosslinkers included transglutaminase, tyrosinase, horseradish peroxidase, laccase, sortase A, genipin, vanillin, tannic acid, and phytic acid. No less important are the reactions involving click chemistry and the macromolecular crosslinkers for polysaccharides and proteins. Literature examples of polysaccharides or proteins crosslinked by the different strategies were presented along with the corresponding highlights. The general mechanism involved in chemical crosslinking mediated by gamma and UV radiation was discussed, with particular attention to materials commonly used in digital light processing. The evaluation of crosslinking efficiency by gravimetric measurements, rheology, and spectroscopic techniques was presented. Finally, we presented the challenges and opportunities to create safe chemical hydrogels for biomedical applications.

Rheological and thermal stability of interpenetrating polymer network hydrogel based on polyacrylamide/hydroxypropyl guar reinforced with graphene oxide for application in oil recovery

The purpose of the present work is to enhance the thermal stability and rheological properties of semi-interpenetrating polymer network (IPN) hydrogel based on partially hydrolyzed polyacrylamide/hydroxypropyl guar (HPAM/HPG) nanocomposite reinforced with graphene oxide (GO), at temperatures (200 and 240 °F) for use in oil recovery applications. FTIR spectra of the IPN nanocomposite hydrogels revealed interactions of GO with HPAM/HPG chains. An increase in the viscosity is also observed from the rheological study. Moreover, IPN and its nanocomposite hydrogels exhibited non-Newtonian behavior. The decline of viscosity of IPN nanocomposite hydrogels was observed with an increase in the temperature from 200 to 240 °F but was still higher than IPN hydrogel without GO. Dispersion of GO through the HPAM/HPG hydrogel matrix was evaluated by SEM morphology and electrical conductivity. The IPN nanocomposite hydrogels showed high viscosity stability, thermal stability, and flow activation energy as compared to IPN hydrogel without GO. Therefore, the addition of 0.1 wt.% of GO to the HPAM/HPG matrix is suitable to create a cross-linked polymer solution with improved properties which may be beneficial for use in oil recovery applications.

Synthesis and properties of organoboron functionalized nanocellulose for crosslinking low polymer fracturing fluid system

The traditional organoboron crosslinker used in the guar gum fracturing fluid has the disadvantages of a larger amount of guar gum and crosslinker and higher susceptibility to pH. Nanoparticles have special properties such as large specific surface area and many active groups, so the organic boron crosslinker and nanoparticles are combined to obtain nano crosslinkers. In this paper, rod-shaped nano-cellulose particles were prepared by acid hydrolysis, and a nanocellulose crosslinker was synthesized by combining with organic boron and KH550. Nanocellulose cross-linker has good temperature and salt resistance. It can meet the requirements of cross-linking guar gum fracturing fluid with a mass fraction of 0.3 wt% under neutral conditions. The residual viscosity is higher than 50 mPa s under shear at 170 s-1 and 110 °C for 60 minutes when the pH increases from 7 to 13, and NBC crosslinking can withstand a temperature of 160 °C under pH = 10. The crosslinking mechanism of the widely accepted nano-crosslinker is that the organoboron on the surface of the nanoparticle combines with the homeopathic ortho hydroxyl of the guar gum molecule to form a hydrogen bond and thereby form a complex network structure. This research shows that the hydrogen bonding between the nano-cellulose crosslinker and HPG molecules, and the resulting gel has a more complex network structure because of the formation of inter-chain cross-links.

Double-Network Hydrogels of Corn Fiber Gum and Soy Protein Isolate: Effect of Biopolymer Constituents and pH Values on Textural Properties and Microstructures

Corn fiber gum (CFG) -soy protein isolate (SPI) double-network (DN) hydrogels were fabricated using laccase and a heat treatment process, in which CFG solution formed the first gel network via laccase oxidation, while SPI formed the second network through heating, as described in our previous research. The aim of this study was to investigate the influences of CFG/SPI constituents (CFG concentration 0-3%, w/v; SPI concentration 8-10%, w/v) and pH values (5.0-7.5) on the textural properties, microstructures and water-holding capacities (WHC) of the CFG-SPI DN hydrogels. Confocal Laser Scanning Microscopy (CLSM) results showed an apparent phase separation when the CFG concentration was above 1% (w/v). The textural characteristics and WHC of most DN hydrogels were enhanced with increasing concentrations of CFG and SPI. Scanning Electron Microscopy (SEM) observations revealed that the microstructures of DN hydrogels were converted from coarse and irregular to smooth and ordered as pH values increased from 5.0 to 7.5. Excellent textural properties and WHC were observed at pH 7.0. This study developed various CFG-SPI DN hydrogels with diverse textures and structures, governed by the concentrations of protein/polysaccharide and pH values, and also contributes to the understanding of gum-protein interactions in DN hydrogels obtained under different conditions.

Evolution of Network Structure and Mechanical Properties in Autonomous-Strengthening Dental Adhesive

The inherent degradation property of most dental resins in the mouth leads to the long-term release of degradation by-products at the adhesive/tooth interface. The by-products increase the virulence of cariogenic bacteria, provoking a degradative positive-feedback loop that leads to physicochemical and mechanical failure. Photoinduced free-radical polymerization and sol‒gel reactions have been coupled to produce a novel autonomous-strengthening adhesive with enhanced hydrolytic stability. This paper investigates the effect of network structure on time-dependent mechanical properties in adhesives with and without autonomous strengthening. Stress relaxation was conducted under 0.2% strain for 8 h followed by 40 h recovery in water. The stress‒time relationship is analyzed by nonlinear least-squares data-fitting. The fitted Prony series predicts the sample’s history under monotonic loading. Results showed that the control failed after the first loading‒unloading‒recovery cycle with permanent deformation. While for the experimental sample, the displacement was almost completely recovered and the Young’s modulus increased significantly after the first test cycle. The experimental polymer exhibited higher degree of conversion, lower leachate, and time-dependent stiffening characteristics. The autonomous-strengthening reaction persists in the aqueous environment leading to a network with enhanced resistance to deformation. The results illustrate a rational approach for tuning the viscoelasticity of durable dental adhesives.

Effect of particle size, concentration, temperature and pH on rheological properties of shallots flour

Shallot flour was prepared and sieved into three different particle sizes of < 180 μm (sample A), 180 μm (sample B) and 250 μm (sample C). Effect of concentration [0.5%, 1.0%, 1.5% and 2.0% (w/w)], temperature (20, 30, 40, 60 and 80 °C), pH (4, 7 and 10) and freezing (- 20 °C) on rheological properties of shallot flour were studied at increasing shear of 0.1-100 s^-1. Effect of dynamic change in temperature (15-95 °C) was also measured at constant shear rate of 50 s^-1. Power law (Eq. 2) model with coefficient of determination (R²) above 0.90, well described the rheological behavior of the shallot flour as a shear thinning, non-Newtonian fluid at different concentration, temperature and pH. All the samples had n values below 1 and increase in viscosity or consistency index (k) value with increase in concentration of the sample was observed, while inverse relation was observed when temperature was increased. All samples showed increase in k value when the pH of the dispersion was varied from acidic to alkaline condition. Viscosity of samples were found unaffected even after freezing in freeze-thaw cycle. These data show sample A to be most suitable for their application as thickener, having highest k value. The obtained research provides information for utilization of shallot as a thickener in various food industries.

Synthesis and characterization of a novel, pH-responsive, bola-based dynamic crosslinked fracturing fluid

Fracturing fluids are important media for hydraulic fracturing. Typically, the fluids are gelled using a polymeric gelling agent. Technological improvements over the years have focused primarily on improving the rheological performance, thermal stability, and the clean-up of crosslinked gels. In this study, novel supramolecular assembly of a low-damage fracturing fluid combining an ionic polymer gel (hydroxypropyl trimethylammonium chloride guar-cationic guar) and a bola surfactant fluid (bola carboxylate polypropylene glycol) is carried out and it is reported to have improved properties and special characteristics due to the synergistic effects of the dual systems, which are different from those of polymer gels and surfactant fluids. The viscosity of the fracturing fluid shows a sudden increase upon an increase in temperature and excellent self-assembly recovery after shearing. The fracturing fluid exhibits pH-responsive viscosity changes and low permeability impairment, due to the formation of a network structure and supramolecular microspheres at different pH values.

Fracturing fluids are important media for hydraulic fracturing.

Reducing adsorption of hydroxypropyl guar gum on sandstone by silicon nanoparticles

Hydroxypropyl guar gum (HPG) is commonly used as the thicker of the fracturing fluid. It will be adsorbed on the sandstone that leads to decrease the permeability of the reservoir. Therefore, it is necessary to reduce the adsorption of HPG to decrease the permeability damage. The effect of silica nanoparticles (SNP) on the adsorption properties of HPG has been studied. X-ray photoelectron spectroscopy is employed to confirm the interaction force between HPG and sandstone. It is clear that hydrogen bonds is an important force of adsorption between HPG and sandstone. SNP can break hydrogen bonds between HPG and sandstone by occupying the rock surface, while altering the wettability of the rock. This results in effectively reducing the amount of HPG adsorption and retaining larger pores of the core after flooding with fracturing fluids. Adding SNP to HPG is an effective method to reduce reservoir damage.

Mussel-inspired dopamine oligomer intercalated tough and resilient gelatin methacryloyl (GelMA) hydrogels for cartilage regeneration

Gelatin methacryloyl (GelMA) hydrogels are widely used for tissue regeneration.

Self-assembly and rheological behaviors of intermacromolecular complexes consisting of oppositely charged fluorinated guar gums

We synthesized fluorinated cationic/anionic guar gums (FCGG and FAGG) and characterized these species using Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy. The degree of fluorine substitution of FCGG (0.26%) and FAGG (0.21%) was calculated by elemental analysis. In addition, we explored the self-assembly and rheological behaviors of FCGG-FAGG complexes by viscometry, scanning electron microscopy, light scattering, fluorescence spectroscopy, and rheometry. The maximum viscosity and molecular weights were observed with a FAGG:FCGG mass ratio of 7.0:3.0, denoted by COMP. Moreover, FAGG-FCGG interactions in COMP led to the lowest shape factor and critical associating concentration. Additionally, the relaxation time and crossover modulus of COMP (6.65 s and 0.90 Pa, respectively) were remarkably higher than those of FCGG and FAGG alone. Finally, viscoelastic hysteresis loops emerged for FAGG and COMP. The results suggested that the self-assembly behaviors of FAGG-FCGG were influenced by both ionic and fluorinated groups.

Characterization of high yield exopolysaccharide produced by Phyllobacterium sp. 921F exhibiting moisture preserving properties

A new strain bacteria was isolated and named as Phyllobacterium sp. 921F, due to its high production capacity of exopolysaccharide (EPS). Characterization of physico-chemical properties of the EPS and optimization for high production were conducted to aim at industrial applications. The optimum pH and temperature were 7.0 and 30°C, respectively. The following scale-up fermentation was carried out in 30L bioreactor and amounts of EPS (21.9g/L) were produced. The EPS with a molecular mass of 1082kDa was composed of glucose, galactose, and pyruvate. The EPS solution behaved as Newtonian at low concentrations (≤0.3%) and as shear thinning at higher concentration (e.g, 1%). The moisture retention ability of the EPS was found to be superior to hyaluronic acid. Results suggest that Phyllobacterium sp. 921F is a good candidate for large-scale production of the EPS which might be utilized in food and cosmetics industries.

Understanding the temperature–resistance performance of a borate cross-linked hydroxypropyl guar gum fracturing fluid based on a facile evaluation method

A facile procedure has been proposed to evaluate the temperature–resistance performance of fracturing fluids, which was used to understand the temperature–tolerance performance of a borate cross-linked hydroxypropyl guar gum fracturing fluid.