Gel Formation Process Research Articles

Evidence for silica gel and its role in faulting in the Tuscarora Sandstone

Silica gel has been proposed as a fault weakening mechanism that may offer a solution to the stress paradox of faulting and be important in promoting seismic slip. Evidence that a gel was present in a fault zone during displacement has proven elusive owing to the unstable nature of a gel and its descendants. Examination of faults in the Middle Silurian Tuscarora Sandstone and other quartz-rich rocks in the region has shown that the microcrystalline quartz in bands and cement in cataclasites was derived from a silica gel. The presence of comminuted grains, silica nanospheres, flow features, amorphous silica, and polygonal crystal domains of low dislocation density within microcrystalline quartz on and adjacent to the fault surfaces is interpreted as evidence of a mobile silica gel precursor. Brecciated microbreccias and mutually crosscutting relationships between microfractures, microcrystalline quartz bands, and microveins along and adjacent to fault surfaces suggest that formation of these features was cyclic. Mutually overprinting textures between brittle and fault creep microstructures (stylolites) indicate alternating episodic brittle deformation and pressure solution. As silica-rich rocks are common, understanding the process of silica gel formation on fault surfaces and its behavior may provide new insights into the mechanics of faulting in the brittle crust.

The underlying mechanism in gel formation and its mathematical simulation during anionic polyacrylamide solution ultrafiltration process.

A dead-end ultrafiltration cup was continuously operated to investigate the underlying mechanisms of membrane fouling caused by gel layer in this paper. Anionic polyacrylamide was used as a model foulant for gel formation process in various ultrafiltration processes by two kinds of ultrafiltration membrane, e.g., polyvinylidene fluoride (PVDF) membrane (OM) and TiO2/Al2O3-PVDF membrane (MM); then, a gel formation model was established and systematically assessed. The results show that the gel formation process in ultrafiltration can be divided into three stages: "slow-rapid-slow" flux decay curve. The R2 value of the simulation curve was still higher than 0.90 for both OM and MM. Based on the current cognition, the proposed gel layer formation mechanism and mathematical model were feasible.

Characterization of the structure and diffusion behavior of calcium alginate gel beads

ABSTRACTA simple and novel method using gel shrinkage to indirectly characterize the structure of calcium alginate gel (CAG) beads during the calcium alginate gelation process was presented in this study. The effect of preparation process parameters (gelling cations, bead diameter, and alginate M w and concentration) on the structure of the CAG bead formation process was thoroughly investigated. It was found that (a) the concentration of the Na+ and Ca2+ ion in gel bath was found to be the determining factor in the gel structure formation process by regulating the dissociation of alginate and the complexation of the calcium; (b) Na+ acts as a competitor with calcium and a screen in the electrostatic repulsion; (c) the effect of beads size below 700 μm on the structure of CAG beads can be neglected; and (d) the sodium alginate concentration has no significant effect on the gel formation process. Furthermore, the diffusion of bovine serum albumin (BSA) was controlled by the density of CAG bead. Consequently, a faster diffusion rate of BSA within the looser structure of beads can be observed. These results are keys to understanding the behavior and performance of beads in their utilization medium. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48923.

Simultaneous measurements of dynamic modulus and turbidity and effects of calcium ions on the process of thrombin-induced fibrin gel formation

Simultaneous measurements of dynamic modulus and turbidity and effects of calcium ions on the process of thrombin-induced fibrin gel formation

The properties and formation mechanism of oat β-glucan mixed gels with different molecular weight composition induced by high-pressure processing.

High pressure, an emerging nonthermal technology has been widely applied in food product modifications. The effects of oat β-glucan concentration and pressure on the properties of mixed gels with the different ratios of varying molecular weight (MW) β-gulcan induced by HPP were investigated. The results showed that the lowest β-glucan concentration forming a gel was 15% at 200 MPa, while 8% β-glucan was required to form a gel at 500 MPa. The gel intensity and textural properties increased with elevating β-glucan total concentration and pressure. The characteristic compact and smooth mixed gel formed with 12% β-glucan at a ratio of 50:50 at 400 MPa for 30 min. Under this optimal parameters, the mixed solution showed a relatively lower particle size and turbidity, and the hydrogen bonding and electrostatic interaction played the main role during the gel formation process by high pressure. In addition, the core molecular structure of β-glucan was maintained in the mixed gel formed under the optimal parameters.

In Situ Crosslinking Bionanocomposite Hydrogels with Potential for Wound Healing Applications.

In situ forming hydrogels are a class of biomaterials that can fulfil a variety of important biomedically relevant functions and hold promise for the emerging field of patient-specific treatments (e.g., cell therapy, drug delivery). Here we report the results of our investigations on the generation of in situ forming hydrogels with potential for wound healing applications (e.g., complex blast injuries). The combination of polysaccharides that were oxidized to display aldehydes, amine displaying chitosan and nanostructured ZnO yields in situ forming bionanocomposite hydrogels. The physicochemical properties of the components, their cytotoxicity towards HaCat cells and the in vitro release of zinc ions on synthetic skin were studied. The in situ gel formation process was complete within minutes, the components were non-toxic towards HaCat cells at functional levels, Zn2+ was released from the gels, and such materials may facilitate wound healing.

Protein structure and sulfhydryl group changes affected by protein gel properties: process of thermal-induced gel formation of myofibrillar protein

ABSTRACT The study investigated the change in protein structure upon thermo-induced gelation of myofibrillar protein (MP, 2%) under different temperatures (30–80°C) at 0.6 M NaCl and pH 6.2. The results showed that heating from 45°C led to changes in physicochemical properties and intermolecular forces involved during MP gelation, which are related to each other. During the heating process, the free sulfhydryl content slowly increased and reached the highest value at 45°C (10.23 ± 0.13 μmol/g protein). When the temperature exceeded 50°C, Ellman’s titration and SDS-PAGE results indicated that MP gel began to form with the formation of disulfide bonds, which contributed to stabilize the gel structure. Gel strength of the heat-induced MP gel formed at 60°C was significantly higher than that at other temperatures (P < .05), reaching 1.12 ± 0.02 N. Strictly speaking, myofibrillar protein gelatinized after 60°C, and water-holding capacity of the MP gel decreased from 60-80°C, and reached a relatively low value at 80°C. Furthermore, Raman spectra showed that the α-helix content decreased with increasing temperature, β-sheets and random coil contents increased, and the content of the twist-twist-trans conformation increased steadily.

Hydrodynamics and mass transfer with gel formation in a roll type ultrafiltration membrane

At this point in history, mankind faces a daunting challenge: how are we to produce high-grade foods without damage to the environment? The only possible rational solution lies in the efficient use of natural raw materials. However, the practical side of the matter cannot be resolved without innovative food equipment designed on the basis of the latest scientific achievements. The current research features the theory and practice of curd whey and skimmed milk ultrafiltration. It focuses on the main operating parameters of the equipment involved and the maximum permissible value of the milk solids content. The experiment included whey, obtained as a byproduct of cottage cheese processing, and skimmed milk, obtained by whole milk separation. The membrane method in the processing of secondary dairy raw materials allows for an environmentally-friendly waste-free production. It is a promising trend in the modern food industry: it creates opportunities for a large range of novel dairy products, beverages, and animal feed, as well as for other sustainable technologies. The paper describes how the volume of permeate flux mass transfer and the selectivity of polysulfonamide ultrafiltration membranes (PSA-20 and PSA-50) depend on the volume of operating load and circulation rate during whey and skimmed milk separation. The authors analyzed the mass transfer and the hydrodynamics in the channel of a roll type baromembrane, including the gel formation process. They established the influence of the milk solids weight ratio in the liquid polydisperse system on the permeate flux volume and the selectivity of the polysulfonamide ultrafiltration membrane (PSA-50).

Role of alkali concentration on reaction kinetics of fly ash geopolymerization

This paper assesses the effect of alkali concentration on the reaction kinetics and mechanism of fly ash geopolymerization. The kinetic parameters of fly ash with different alkali (6–10 M NaOH) solution have been determined by using heat of reaction data measured at isothermal conduction calorimeter at different reaction temperatures, 34–60 °C. With increasing alkali concentration the peak gets intensify and position shifts towards higher time and total heat of reaction enhances. At higher alkali concentration amount of Al and Si dissolute increases, thus, higher energy is required to initiate and forward the reaction. However, the kinetic parameters are varying with alkali, but no alternation is determined in the involved reaction mechanism, nucleation and growth. The apparent activation energy has been evaluated by rate method, suggests three main steps such as dissolution, gel formation and restructuring process of geopolymer reaction. Fly ash geopolymerization is kinetically favored in between 39 and 45 °C temperature with all alkali concentration in experimented condition.

Вивчення особливостей процесу осадоутворення силікатно-лужної композиції в присутності морської води

Мета: Метою цієї статті є дослідження процесу осадоутворення при розведенні розчину силікату морською водою. Проаналізіровано зміну процесу осадоутворення зі збільшенням рН вихідного розчину силікатно-лужної композиції. Методи дослідження: Для визначення відносної концентрації силікату в надосадовій рідині використовувалися методи прямого і зворотного титрування; рН-метрія – для контролю за зміною рН силікатно-лужних композицій в процесі експерименту. Результати: найбільш інтенсивно процес осадоутворення відбувається при співвідношенні силікату в морській воді в суміші 40 ÷ 60; зі збільшенням рН вихідної композиції кількість осаду при змішуванні з морською водою послідовно зменшується; для утворення гелю достатньо, щоб залишкова концентрація силікату в розчині становила 1,5–2 % мас; найбільш значні зміни рН композицій відбувається при вмісті в суміші морської води понад 50 %. Обговорення: З метою визначення мінімальної концентрації силікату, необхідною для утворення гелю при змішуванні силікатних композицій з морською водою, необхідно визначати концентрацію силікату в надосадовій рідині (фільтраті). Було встановлено, що кількість силікату в надосадовій рідині збільшується для всіх співвідношень силікату і морської води зі збільшенням рН вихідної композиції, причому для досягнення однакової концентрації силікату в надосадовій рідині зі збільшенням рН збільшується частка морської води в суміші. Виявлено, що утворення гелю (для композиції з вихідним значенням рН = 11,72) відбувалося при залишковій концентрації силікату в розчині 0,25-0,3 від вихідної. Таким чином, було встановлено, що мінімальна концентрація силікату в розчині може становити 1,5-2,0% мас.

Formation of a Bile Salt-Drug Hydrogel to Predict Human Intestinal Absorption

The unique character of bile salts to self-assemble into hydrogels in the presence of halide salts was exploited in this work to facilitate the prediction of human intestinal absorption (%HIA) for a set of 25 compounds. This was achieved by firstly incorporating each compound separately within the process of gel formation to create a series of gel-drug membranes. Scanning electron microscopy analysis of the freeze-dried samples of the blank bile salt hydrogels and drug-loaded bile salt hydrogels indicated a unique microstructure made of a network of intertwined fibrils. Drug-loaded sodium deoxycholate hydrogels were then utilized as the donor phase to study permeability using flow-through and static diffusion cells. The resulting values of the release-permeability coefficient (Kp) were then analyzed, along with other molecular descriptors, for the %HIA using multiple linear regression. Overall, when comparing predicted values (using the systems presented in this study) with known literature values, it can be seen that both methods (i.e., using static and flow-through cells) had good predictability with R2PRED values of 79.8% and 79.7%, respectively. This study therefore proposes a novel, accurate, and precise way to predict HIA for compounds of pharmaceutical interest using a simple in vitro permeation system. It is important to develop alternatives to the current methods used in prediction of HIA, which are expensive and time-consuming or include the use of animals. Therefore, the proposed method in this study being economic and time-saving provides superiority over these current methods and suggests the possibility of its use as an alternate to such methods for prediction of HIA.

Formulation and evaluation of in situ herbal gel containing aqueous and methanolic extract of fruits of Quercus infectoria Oliv. for vaginal application

Conventional vaginal dosage forms frequently produce leakages and drip. There is a need for the development of innovative vaginal formulation technology that fulfills certain criteria such as desirable product dispersion throughout the vagina, retention for intended intervals, and adequate release of drug. These features can be achieved by the use of bioadhesive based novel delivery systems. In-situ gelation is a process of gel formation at the site of application after the composition or formulation has been applied the site. Formulation and evaluation of one such bioadhesive based novel drug delivery system for an effective and patient friendly use of an antifungal drug to formulated In-situ gel. Quercus infectoria is medicinally important plant grown wildly in India and is useful in the treatment of fungal and microbial infection by tribal’s of India. The plant is used by tribal women to treat vaginal infection as mentioned in folk-lore. Therefore, the present plant as selected to formulate in-situ herbal gel using Quercus infectoria as active ingredients for the treatment of vaginal infection.&#x0D; Keywords: Herbal Gels, Quercus infectoria, bioadhesive, vaginal drug delivery

Changes of structural and physical properties of semi-gel from Alaska pollock surimi during 4 °C storage

This study compared the semi-gel system of Alaska pollock surimi formed at a low temperature with a heat-induced gel system. The cold semi-gel and heat-induced gel were found to have obvious differences in their degrees of protein unfolding, aggregation, and gel network structures. Microscopic observations and an analysis of their fractal dimensions revealed different degrees of compactness and uniformity in the two network structures. Rheological parameters, including the least permanent deformation, equilibrium stress, and frequency exponent, confirmed the non-total aggregation and lower degree of cross-linking in the cold semi-gel. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the myosin heavy chain (MHC) value gradually decreased, but the light meromyosin (LMM) value remained stable during cold storage. Furthermore, a decrease in the α-helix and an increase in the β-sheet and random coil values, as revealed by Fourier-transform infrared (FT-IR) spectroscopy, indicated that the proteins unfolded differently in the two gel systems. By comparing the times required for the cold semi-gel and heat-induced gel to form, we concluded that the formation process of heat-induced gel is intertwined while it is temporally separated in cold storage. Overall, myosin was selected as the starting point for establishing a schema chart to characterize the gelation processes of the cold semi-gel and heat-induced gel. These findings are helpful for understanding the gelation process of surimi in refrigerated storage.

Synthesis, structure, and properties of bisphenol A formaldehyde sol—precursor of low-density aerogel

Low-density organic aerogels (down to 11–12 mg/cm3) were successively synthesized by polycondensation of formaldehyde with bisphenol A (2,2-diphenylolpropane or BPhA) methylol derivatives by the thermal treatment under basic conditions. In this paper, the main features of bisphenol A-formaldehyde (BF) sol and hydrogel formation have been examined for the first time. The molecular weight distribution both of the initial resin and the soluble products of its thermal processing were studied by size exclusion chromatography. A detailed study of the structure of sols and the dynamics of its change was carried out by dynamic and static light scattering and scanning and transmission electron microscopy. The results obtained allowed to describe the process of gel formation as a diffusion-limited cluster-cluster fractal aggregation of sol nanoparticles formed during the polycondensation. Crosslinking of low-density fractal aggregates leads to the formation of a macro-porous structure with a high pore volume and, ultimately, to a low-density aerogel.

Protolytic properties influence of the dispersion medium on the process of silicic acid polycondensation

The paper presents a procedure for the preparation of sodium polysilicate from silica hydrosol for use as an additional binding agent in the production of composite materials based on wood matrix. It is proved that 3-stages mechanical activation of low quality sand makes it possible to obtain silica particles with sizes on the upper boundary of the ultradispersed range (100 nm). The effect of dimensional characteristics, the zeta potential of the surface of silica particles, and the protolytic properties of the dispersion medium on the gel formation process is studied. The obtained dependence of the zeta potential of particles from the pH of diluent has shown that in acidic region have equivalence point and a low zeta-potential area in which the colloidal particles become unstable (which may lead to rapid gelification in the system). It is proposed to accelerate the process of depolarization of silica particles by maintain the pH value of the dispersion medium equal to 2-4, this will quickly produce a large yield of gel-like sodium polysilicate.

SINTESIS DAN KARAKTERISASI XEROGEL HASIL KOPRESIPITASI DARI PASIR PANTAI PANJANG BENGKULU

[SYNTHESIS AND CHARACTERIZATION OF XEROGEL RESULTS OF COPRECIPITATION OF LONG BEACH BENGKULU BEACH]. This research aims to synthesize and characterization to Xerogel which synthesizes from Pantai Panjang sands Bengkulu. The method used for this study to synthesizes Xerogel is to use the coprecipitation method. Qualitative XRF test against raw sand materials that were used show that the content of the element is the most significant element of Si. The first stages of the synthesis of Xerogel is a purification of the sand sample.. Xerogel synthesis is carried out in two phases, namely the manufacture of aqueous solutions of Sodium Silicate and continued with the formation of a gel. The production of Sodium Silicate solution is done using the NaOH concentration at 5, 6 and 7 M. Gel formation process is done by adding a solution of HCl 10 M into the solution of Sodium Silicate, followed by process of filtration, washing and drying in the oven. The results showed that the optimum conditions of synthesis of Xerogel obtained using 6 M NaOH , with a yield obtained is amounting at 0.8%. The results of the test by XRD shows that the silica crystal structure on Xerogel are amorphous-shaped. SEM-EDS test results show that the acquired Xerogel on research has a smooth texture and size is not homogeneous with the highest content of elements are the elements Si and O. PSA test shows that particle size in Xerogel an average at 191.4 nm.

A novel process for peanut tofu gel: Its texture, microstructure and protein behavioral changes affected by processing conditions

This work reports, a novel method of peanut tofu preparation by combining transglutaminase (TG) and high-temperature pressure cooking (HTPC, 115 °C, 0.17 MPa) treatment, and its gel formation was studied. Texture and Scanning electron microscope (SEM) results showed TG addition (0.75 mg/g) significantly improved the tofu texture (p < 0.05), with a denser network composed of relatively even pores, whereas the excessive addition (1.25 mg/g) resulted in a softer tofu. At all concentrations (0.25–1.25 mg/g), TG treatment induced the crosslinking of protein molecules as proved by SDS-PAGE, particle size and apparent viscosity analyses. DSC measurement indicated that the subsequent HTPC treatment was able to denature peanut proteins completely. Moreover, by analyzing the changes in surface hydrophobicity (H0) and total free sulphydryl content (TFS) during processing, we found that hydrophobic interactions and disulfide bonds were the major forces involved in the formation of peanut tofu gel. This study suggests this novel method could be applied to make peanut tofu and provides a basis for understanding its gel formation process.

Effects of ultrasonic treatment on gel rheological properties and gel formation of high-methoxyl pectin

To explore modification effects of ultrasonic treatment on high-methoxyl pectin (HMP), HMP was used as raw material and processed by ultrasonic treatment under different powers (120, 240, 360 and 480 W). Rheological properties of HMP gel were tested. Moreover, the HMP gel formation process was analyzed through kinetic analysis. Results demonstrate that the viscosity of HMP was reduced significantly by ultrasonic treatment. However, the rheological properties of HMP gel were retained, and they still showed typical pseudoplastic and shear thinning properties. HMP gel of the low-power treatment group showed better viscoelasticity compared with those of the contrast group. The maximum G′ and G″ were achieved after HMP was treated by 120 W ultrasonic power when elasticity of HMP was enhanced significantly. Moreover, the structure of HMP was damaged by the cavitation effect and mechanical effect as ultrasonic power increased, thereby the strength of gel decreased significantly. Ultrasonic treatment could weaken the gel formation ability of HMP. During gel formation, the activation energy difference between the high-temperature and low-temperature stages reduced with increasing ultrasonic power. The 120 W treatment group achieved the maximum activation energy difference between the high-temperature and low-temperature stages, while the 480 W treatment group achieved the minimum activation energy difference.

Effect of including a gas layer on the gel formation process during the drying of a polymer solution.

In this paper, we study the influence of the upper gas layer on the drying and gelation of a polymer solution. The gel is formed due to the evaporation of the binary solution into (inert) air. A one-dimensional model is proposed, where the evaporation flux is more realistically described than in previous studies. The approach is based on general thermodynamic principles. A composition-dependent diffusion coefficient is used in the liquid phase and the local equilibrium hypothesis is introduced at the interface to describe the evaporation process. The results show that the high thickness of the gas layer reduces evaporation, thus leading to longer drying times. Our model is also compared with more phenomenological descriptions of evaporation, for which the mass flux through the interface is described by the introduction of a Peclet number. A global agreement is found for appropriate values of the Peclet numbers and our model can thus be considered as a tool allowing to link the value of the empirical Peclet number to the physics of the gas phase. Finally, in contrast with other models, our approach emphasizes the possibility of very fast gelation at the interface, which could prevent all Marangoni convection during the drying process.

Structural properties of waxy corn and potato starch blends in excess water

The structural properties of blends of waxy corn starch and potato starch at different proportions were evaluated at 20% solids content. The results from differential scanning calorimetry, wide-angle X-ray scattering, and small-angle X-ray scattering of the starch blends indicated that each starch gelatinized completely and independently. The setback viscosity values were higher in the blends compared with native starches, which suggested that the granular interactions had an important effect. The presence of waxy corn starch granules could have reinforced the network formed by amylose leached from potato starch granules. The intrinsic characteristics of waxy corn starch and potato starch determined the type of granular and molecular interactions that could be carried out during the processes of gelatinization and gel formation in starch blends.