Swelling Behavior of Guar Gum-g-Poly(Sodium Acrylate -co-Styrene)/Attapulgite Superabsorbent Composites

A series of superabsorbent composites, guar gum-g-poly(sodium acrylate-co- styrene)/attapulgite [GG-g-P(NaA-co-St)/APT], were prepared by simultaneous grafting partially neutralized acrylic acid and hydrophobic styrene (St) onto guar gum in the presence of attapulgite as an inorganic component. Equilibrium swelling capacity strongly depended on the concentration of St, drastically increasing with increasing St concentration to 24.3 mmol/L and then decreasing. The influence of St concentration on the swelling kinetics of the superabsorbent was studied by means of a Schott's second-order model. The proper amount of St is of benefit for the improvement of the initial swelling rate in either distilled water or saline solution. The influence of St concentration on the swelling behaviors in various external media (the aqueous solutions of various salts, pHs, hydrophilic organic solvent/water mixture and surfactants) was also investigated systematically. Results showed that the concentration of St is the key factor influencing equilibrium swelling capacity of the superabsorbent composites in each swelling media, and moderate amounts of St could enhance the responsiveness of the corresponding superabsorbent composite to external stimulation.     

黄原胶发酵液蒸发器的传热性能研究

对黄原胶发酵液的蒸发浓缩进行了研究,测定了以3种不同传热管为传热面的蒸发器的传热和流体阻力性能．结果表明,以强化管为传热面的蒸发器的阻力有所提高,但其传热系数也得到了提高,是普通管的3．6倍左右．黄原胶发酵液的浓度从发酵终了时的2．5％～3．2％经浓缩提高到4．5％～5．0％,发酵液体积减小近1/2,从而有效地降低了目前黄原胶后提取过程中的溶剂周转使用量、消耗量和提取成本。     

Fast and excellent healing of hydroxypropyl guar gum/poly(N,N‐dimethyl acrylamide) hydrogels

In this article, a fast and high efficient healing hydroxypropyl guar gum (HPG)/poly(N,N‐dimethyl acrylamide) (PDMA) hydrogel is prepared by a facile synthesis method. HPG networks are formed through hydrogen‐bond interaction between the hydroxyl groups in the HPG chains, and PDMA networks are self‐crosslinked without any chemical crosslinker. The cut hydrogel could heal when nanosilica solution is chosen as the connector that is related to the adsorption of polymer to the surface of nanosilica. The fracture stress of the HPG/PDMA gels presents a fast and almost full recovery within a short time (1 min), while the recovery of fracture strain and elastic modulus is related to time in 2 h. The healing efficiency of HPG/PDMA gel is investigated as a function of healing time, HPG content, and N,N‐dimethyl acrylamide content. The microscopic healing process and healing mechanism are also discussed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 239–247     

Electrical conductivity,impedance, and percolation behavior of carbon nanofiber and carbon nanotube containing gellan gum hydrogels

The electrical impedance behavior of gellan gum (GG), GG–carbon nanotube, and GG–carbon nanofiber hydrogel composites is reported. It is demonstrated that the impedance behavior of these gels can be modeled using a Warburg element in series with a resistor. Sonolysis (required to disperse the carbon fillers) does not affect GG hydrogel electrical conductivity (1.2 ± 0.1 mS/cm), but has a detrimental effect on the gel's mechanical characteristics. It was found that the electrical conductivity (evaluated using impedance analysis) increases with increasing volume fraction of the carbon fillers and decreasing water content. For example, carbon nanotube containing hydrogels exhibited a six‐ to sevenfold increase in electrical conductivity (to 7 ± 2 mS/cm) at water content of 82%. It is demonstrated that at water content of 95 ± 2% the electrical behavior of multiwalled nanotube containing hydrogels transitions (percolates) from transport dominated by ions (owing to GG) to transport dominated by electrons (owing to the carbon nanotube network). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 864–871     

Rheokinetic study of gel-breaking process of xanthan gum solution

The dynamic rheological behavior of xanthan gum (XG) during the gel-breaking process was studied in this work. Both experimental and numerical simulations were adopted to investigate the effects of temperature and added salt on the gel-breaking process. The results showed that the gel-breaking reaction is slowed down by the added salt, while temperature has a positive influence on the chemical degradation of XG. The novel rheokinetics equations were established to describe the gel-breaking process of XG and the simulated values are in good agreement with experimental data. The changes of the model parameters with respect to temperature and added salt are consistent with the experimental results obtained with rheometer, which verifies the feasibility of the established rheokinetics equations for characterizing the gel-breaking reaction of XG.     

Synthesis,characterization, and hoping transport properties of HCl doped conducting biopolymer‐co‐polyaniline zwitterion hybrids

A series of electrically conductive zwitterion hybrid materials were facilely synthesized with anionic acacia gum (AG) and cationic HCl doped polyaniline (PANI) through radical copolymerization method. A representative acacia gum‐polyaniline hybrid (AG‐PANI) was characterized using UV‐vis, FTIR, ¹H NMR, and SEM. HCl doped AG‐PANI possesses zwitterion character due to the presence of NH on PANI and ? COO^? of AG. The cyclic voltammogram of AG‐PANI showed three anodic peaks at 0.20 V, 0.58 V, and 0.64 V along with two cathodic peaks at 0.50 V and 0.40 V with large capacitive background currents. AG‐PANI exhibited electrical conductivity that was found dependent on the ratio of aniline to AG, temperature, and pH. Its electrical conductivity versus temperature plot indicated Mott's nearest‐neighbor hopping mechanism at the temperature range 83–323 K. The hybridization of AG and PANI yielded eco‐friendly advanced functional materials for technological applications. Copyright © 2008 John Wiley & Sons, Ltd.     

Development of sterculia gum based wound dressings for use in drug delivery

The present study deals with the modification of sterculia gum to develop the novel wounds dressing for the delivery of antimicrobial agent (tetracycline hydrochloride). The sterculia crosslinked PVA (sterculia-cl-PVA) hydrogels were characterized by FTIR and swelling studies. For the evaluation of swelling and drug release mechanism, the swelling kinetics and in vitro release dynamics of model drug from this matrix were studied in solution of different pH and simulated wounds fluid. Per gram of polymer has taken (8.3 ± 0.1) g of simulated wounds fluid and has released (0.820 ± 0.6) mg of drug in the simulated fluid. The value of the ‘n’ (0.84) indicates the non-Fickian diffusion mechanism for the release of drug in simulated fluids.     

Viability of Biopolymers for Enhanced Oil Recovery

Xanthan gum and scleroglucan are assessed as environmentally friendly enhanced oil recovery (EOR) agents. Viscometric and interfacial tension measurements show that the polysaccharides exhibit favorable viscosifying performance, robust shear tolerance, electrolyte tolerance, and moderate interactions with surfactants. Non-ionic surfactants and anionic surfactants bind to xanthan gum and transform the backbone conformation from a strong helix to a more flexible structure, reducing the viscosifying efficacy of xanthan. In contrast, non-ionic surfactants and anionic surfactants bind to scleroglucan and increase the viscosifying efficacy by non-electrostatic interactions or imparted electrostatic effects. The two polysaccharides are technically viable as viscosifying agents in typical EOR injection fluid formulations.     

阳离子瓜尔胶与黄原胶的凝胶化性能研究

阳离子瓜尔胶 3 氯 2 羟丙基三甲基氯化铵与黄原胶共混产生协同效应 ,生成凝胶 .研究了共混比例r =m(CG 40 )∶m(黄原胶 ) ,共混温度 ,体系盐离子浓度 ,恒温时间及 pH值对凝胶化的影响 .结果表明 ,当多糖总浓度为 4% ,共混比例为 2 0∶80 ,共混温度为 60℃ ,盐离子浓度为 1.0mol·L-1,恒温时间为 3 0min时 ,可达最大凝胶强度值 ;最适 pH值为 7.0 .并从FTIR谱图上分析了这两种多糖共混凝胶化的作用机理     

Effects of the thermal history and concentration on the aggregation of Erwinia gum in an aqueous solution

The aggregation of Erwinia (E) gum in a 0.2 M NaCl aqueous solution was investigated by multi‐angle laser light scattering and gel permeation chromatography (GPC) combined with light scattering. The GPC chromatograms of five fractions contained two peaks; the fractions had the same elution volume but different peak areas, suggesting that aggregates and single chains coexisted in the solution at 25 °C. The apparent weight‐average molecular weights (M_w) of the aggregates and single chains for each fraction were all about 2.1 × 10⁶ and 7.8 × 10⁴, respectively. This indicates that the aggregates were composed of about 27 molecules of E gum in the concentration range used (1.0 × 10⁻⁶ to 5.0 × 10⁻⁴ g/mL). The weight fraction of the aggregates (w_ag) increased with increasing concentration, but the aggregates still existed even in an extremely dilute solution. The fractionation process and polymer concentration hardly affected the apparent aggregation number but significantly changed w_ag. The E‐gum M_w decreased sharply with an increase in temperature. When the E‐gum solution was kept at 100 °C, w_ag decreased sharply for 20 h and leveled off after 100 h. Once the aggregates were decomposed at a higher temperature, no aggregation was observed in the solution at 25 °C, indicating that the aggregation was irreversible. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1352–1358, 2000