Papers by Keyword: Hydrogel

Abstract: Hydrogel spheres made of sodium polyacrylate with free absorption of water can increase in volume by 100-1000 times due to the violation of the balance of forces of attraction and repulsion between the links of the gel. The addition of water will shift the balance in favor of the repulsive forces. This property will allow them to be used in cement systems as an active expanding aggregate, which will compact the structure, reduce the water-cement ratio during the formation of the cement paste structure, and then give water to the hardening cement stone. The hydrogel sphere itself will decrease in volume to its initial state and will leave the pore in its place. The resulting material can be considered aerated concrete with compacted inter-pore partitions. The advantage of this method over the traditional method of self-compacting masses is that there is no need to supply thermal energy to activate the expansion of the active aggregate, for example, by passing an electric current through the hardening mass. In this article, the properties of the hydrogel are investigated, the dynamics of the expansion of hydrogel spheres in water at different temperatures is determined.

Abstract: This study aims to determine the absorption and ability of hydrogels to hold water. The hydrogel was synthesized using the freeze-thaw method, then the absorption ability and water retention time in the hydrogel were tested and characterized by FTIR and trinocular stereo microscope. The FTIR results showed that the resulting hydrogel had N–H, O–H, aliphatic C–H, bend N–H, C–O, and C–N functional groups. The highest absorption of the hydrogel with a ratio of cellulose:chitosan:EDTA variations of 2:2.25:0.25 (g) respectively, which was 287.46% and the appearance of the hydrogel under a microscope showed that the structure of the hydrogel was rather hollow, so that it affected its absorption.

Abstract: Flexible supercapacitors have attracted more and more attention and research because they can be used as energy storage devices for future flexible electronic devices. In the existing research, graphene has been used to make supercapacitor electrodes, but usually these electrodes have very low specific capacitance or flexibility. Here, a three-dimensional graphene hydrogel for the fabrication of flexible supercapacitors was presented, and the preparation of flexible supercapacitors based on three-dimensional graphene hydrogels was given. Through the research, we find that the prepared flexible supercapacitor has excellent capacitance characteristics, such as high specific capacitance of 168F/g and excellent mechanical flexibility. This study shows that the three-dimensional graphene macro structure has great potential in the preparation of high-performance flexible energy storage devices.

Abstract: In this study, PVA/CS composite hydrogels were prepared by means of freezing and thawing cycles of agricultural wastes, corn straw (CS) and polyvinyl alcohol (PVA). The mechanical properties of the composite hydrogels were analyzed by universal tensile device. The effects of CS on tensile strength and elongation at break of PVA/CS composite hydrogels were analyzed. On the other hand, PVA and PVA/CS composite hydrogels were also freeze-dried to investigate the mechanical properties of all hydrogels after drying.

Abstract: Current available methods for water desalination are energy intensive, expensive, and not feasible for small-scale applications. As an alternative, hydrogels may be utilized as a draw agent and semi-permeable membrane forward osmosis by acting as both to desalinate water. This study aims to synthesize and characterize hydrogels made from cellulose derivatives and reduced graphene oxide nanofillers in order to desalinate and remove microbes from seawater without requiring a large energy input. The hydrogels are formed by combining carboxymethyl cellulose, hydroxymethyl cellulose, reduced graphene oxide, and water to form a paste which is soaked in a crosslinking solution made of citric acid. Swelling, compression, antimicrobial efficiency and desalination efficiency tests were done. The hydrogel that obtained the highest values has a swelling ratio of 1,447%, compressive strength of 4 bar, desalination efficiency of 30%, and antimicrobial properties.

Abstract: Intraperitoneal adhesion is a serious case that often occurs with a prevalence of 90-97 % after undergoing gynecological surgery and laparotomy. This study aims are to characterized the hydrogel and identified the optimal composition of Hyaluronic acid (HA) - N, O-carboxymethyl chitosan (NOCC) as an anti-adhesion biomaterial barrier. The synthesis method involved firstly the synthesis of aldehyde derivative of hyaluronic acid (AHA) and also the conversion of chitosan into its derivative, N,O-carboxymethyl chitosan. These two compounds were mixed in various compositions and crosslinked to form N, O-carboxymethyl chitosan (NOCC) /AHA. Fourier-transform infrared spectroscopy has confirmed that the functional groups found -C = O stretching at 1644 cm^-1 indicating the hyaluronic acid and carboxymethyl group (-CH2COOH) in 1380 cm^-1 which indicate the presence of chitosan. The crosslink is evidenced by the group C = N stretching at a wavenumber of about 1630 cm^-1. The best composition of intraperitoneal anti-adhesion is the ratio of hyaluronic acid: chitosan at 30:10 mg/ml. The swelling test is showed a swelling ratio of around 211.8 % in accordance with the standard as intraperitoneal anti-adhesion. Hydrogel has a degradation rate up to 86.87 % on day 10, and this is in accordance with the standard as intraperitoneal anti-adhesion. Cytotoxicity assay showed that hydrogel was nontoxic with a percentage of 92.9 % cell viability. The newly developed hyaluronic acid-carboxymethyl chitosan has characteristics that conform to the criteria of an intraperitoneal anti-adhesion.

Abstract: Urea is high solubility nitrogen fertilizer. There is major nitrogen pollution in ecosystem. Slow-release nitrogen fertilizer the way to decrease nitrogen form agriculture. Slow-release nitrogen fertilizer the way to decrease nitrogen in agriculture. Slow-release formulations of nitrogen fertilizer were developed based on alginate-gelatin by using calcium chloride as the cross-linker in the egg-box model as hydrogels. Water-retaining ratio, loading behavior, and the release kinetics were examined. The release kinetic rates were investigated by Zero-order kinetic, First-order kinetic, Higuchi, Korsmeyer-Peppas, Weibull, and Hixson-Crowell models. The results showed that the S1G0.5 sample (alginate 1 g and gelatin 0.5 g) was the optimum condition for application as urea slow-release fertilizers because it was a minimal release kinetic rate for 12 hrs. These results indicate that the alginate-gelatin hydrogel can be a slow-release nutrient to plant an environmentally friendly fertilizer.

Abstract: A novel slow-release N-fertilizer hydrogel beads were developed using sodium alginate (SA) and alginate-talcum (ST) composite as N-absorbent. In this work, the hydrogel composite were fabricated by simple method and low cost. N-fertilizer hydrogel beads were prepared two types, for SA types, which were different sodium alginate (1(SA1), 3(SA3), 5(SA5), 7(SA7), and 10(SA10) wt%). And, for ST types, sodium alginate and talcum were vary ratios to 1:0.5(S1T0.5), 1:1(S1T1), and 1:2 (S1T2). The chemical structure of hydrogel composite beads were characterized via Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The release behavior were investigate by Zero-order kinetic model, First-order kinetic model, Higuchi model and Korsmeyer-Peppas model. We have found that the N-fertilizer release constants in Korsmeyer-Peppas model were decrease with increase SA content for 1-5 wt% in SA hydrogel beads. However, SA contents were more than 5 wt% which rapidly enhanced fertilizer release. In addition, to add talcum in ST hydrogel beads significantly reduced fertilizer release rate. The N-fertilizer hydrogel beads exhibits significantly slow release behavior. These results indicates that the development of slow-release fertilizer hydrogel beads can be improve the effectiveness of N-fertilizer.

Abstract: Hydrogels are cross-linked polymeric structures, which consist of up to approximately 90% water, the remainder is polymer chain. Retention of large volumes of water in the intermolecular space is related to the presence of hydrophilic functional groups in the network. The unique hydrogels properties, such as porosity, and biological and mechanical properties, make them suitable for a wide range of applications, especially in the medical sector. Furthermore, ease of modification and good printability are expected in 3D bioprinting technologies. Nevertheless, to maintain their structure and softness, hydrogels must be stored in suitable conditions to prevent water vaporization. The water removal from the hydrogel network results in weight reduction, structural and volumetric changes. It is a considerable challenge for the printouts manufactured by 3D bioprinting technology, where hydrogel products are exposed to drying during the production process, which may affect their shape change and shrinkage. The paper presents a crosslinking process of a hydrogel-based on sodium alginate and the shrinkage of dried hydrogels depending on the crosslinking procedure. An investigation focused on the alginate hydrogel water content, as well as shrinkage of alginate hydrogel degree depending on the concentration of the cross-linking (CaCl₂) solution and the duration of the process. For longer cross-linking time or using higher cross-linking agent concentration, the cross-linking was more efficient. However, it is necessary to optimize the parameters for the bioprinting process.

Abstract: Some hydrophilic drugs (e.g. anti-tumor drug of doxorubicin (DOX) and anti-osteoporosis drug of alendronate sodium (ALN)) have great toxic and adverse effects on the human body. In this paper, two kinds of drug-loaded composite gel systems were prepared via mild and efficient chemical reaction synthesis, hyaluronic acid-linked ALN (HA-ALN) hydrogel and polyethylene glycol-linked DOX (Tetra-PEG-DOX) hydrogel. By characterizing their chemical structures, morphological networks, and ultraviolet absorption behaviors, two different types of drug-loaded composite gels can be constructed well. It is expected to achieve effective drug loading and controlled release. The two drug-loaded gels are applied in the fields of antitumor and anti-osteoporosis and exert their application value in the field of biomedicine.