Delayed crosslinking polymer gel systems are widely used in-depth profile control technology for water production control. In this paper, an amphiphilic polymer P(AM-NaA-DDAM) was synthesized by a free radical micellar polymerization method and a delayed crosslinking amphiphilic polymer gel system was prepared based on multiple emulsion of W1/O/W2 emulsion which was prepared by a two-step emulsification method. The optimized formulation of amphiphilic polymer gel systems is: 0.15% P(AM-NaA-DDAM), 0.3% methenamine, 0.02% resorcinol, and 0.3% citric acid. The delayed gelation time of the delayed crosslinking amphiphilic polymer gel system is closely related to the stability of the W1/O emulsion. By using multiple emulsion delayed crosslinking method, the delayed crosslinking amphiphilic polymer gel system with diesel as the oil phase can delay the gelation time up to 168 hours. 相似文献
Catechin-loaded calcium pectinate gel beads prepared by internal gelation were characterized for their catechin entrapment efficiency and release behavior. The entrapment efficiency was higher when the beads were prepared with a lower catechin-to-pectin ratio, shorter gelling time, higher pectin concentration, and lower acetic acid concentration. The entrapment efficiency was much higher under all tested conditions, when the beads were prepared by internal gelation instead of external gelation. The catechin release was slower for the beads prepared with lower catechin-to-pectin ratio, longer gelling time, and higher concentrations of pectin and acetic acid in both simulated gastric and intestinal fluids. Antioxidant power of catechin was effectively maintained in alkaline simulated intestinal fluid when catechin was entrapped within the beads, compared to cases where it was not entrapped, indicating that the beads can protect catechin molecules from the alkaline environment and release them in a sustained fashion. 相似文献
The gelation process of organically polymer gel was investigated by dynamic thickening measurements. Rheological measurements were used to evaluate the viscosity of the gel. During the gelation process, high temperature resulted in higher rate of crosslinking. Rigid and stable gel was formed in neutral and alkaline media, and the higher of the pH value, the faster of the gelation process. However, gel could not be formed in acid condition. Moreover, the rate of crosslinking increased with the increase of concentration of polymer and crosslinker. The addition of NH4Cl elongated the gelation time significantly, but played a negative role in the gel strength, while a rigid gel was formed in the presence of Sodium acetate or trisodium citrate dehydrate. This paper summarizes the results and discusses how various parameters affect the gelation process of the gel. 相似文献
Summary: We developed a novel thermo‐reversible gelation system by mixing xyloglucan with an iodine solution. Xyloglucan dissolves in water to produce a colorless solution. However, the addition of iodine solution induces color and gelation; heating causes the gel to melt and become colorless. According to results from spectroscopic and small‐angle X‐ray scattering experiments, the gelation mechanism was proposed to involve two xyloglucan chains that associate side‐by‐side and incorporate iodine and/or iodide ions.
Xyloglucan gel prepared by mixing xyloglucan and iodine solution and heating to 60 °C, followed by cooling. 相似文献
Summary: We report a study of thermoreversible gelation of polybenzimidazole (PBI) in phosphoric acid (PA). The PBI gel in PA exhibits fibrillar network morphology and reversible first order phase transition. The gelation rate is measured by the tube tilting method and found to depend both upon gelation concentration and gelation temperature. The UV‐vis study demonstrates that the gelation process is a two‐step process: conformational transformation and aggregation which produces crystallites for gel formation. The WAXS study supports the presence of crystallites in the gel. The PA doping level of the membrane increases significantly because of gelation.
Thermoreversible gelation of polybenzimidazole in phosphoric acid and the membrane produced from the gel. 相似文献
A new method for determining the degree of conversion of gelation (gel) and gel time (tgel) at gel point using a single technology, DSC, is discussed in this work. Four kinds of thermoset resins are evaluated. It is found that the mutation points of reduced reaction rate (Vr) vs. reaction conversion () curves, corresponding with the changes of reaction mechanism, represents the gelation of the reaction. The at the mutation point is defined as gel. From isothermal DSC curves, the point at gel is defined astgel. Traditional techniques (ASTM D3532 and DSC method) are also used to determine gel andtgel in order to demonstrate this new method. We have found that the results obtained from this new method are very consistent with the results obtained from traditional methods. 相似文献
Variations in the starting materials, solvent, catalyst, and water to alkoxide ratio affect gel times and gel properties in sol-gel reactions. Silicon tetraacetate-derived sols gel surprisingly quickly. This paper discusses the acid catalyzed hydrolysis and condensation of silicon tetraacetate in an attempt to understand this rapid gelation. 29Si and 1H NMR spectra show that tetraethoxysilane is an intermediate, and ethyl acetate is produced via a secondary reaction. A correlation between gel times and H+ concentration is demonstrated. 相似文献