Purification,structural data and biological properties of polysaccharide from Prunus amygdalus gum

This work demonstrates the efficiency of almond gum polysaccharides (AGPs) as bioactive compounds. AGPs were first extracted using H₂O₂, in the presence of NaOH, at different times and temperatures. The optimal extraction conditions were 4% H₂O₂ and 2 N NaOH, for 7 h at 50 °C, leading to an extraction yield of 58.2% (w/w). After a purification step, the retained AGPs were characterised using high‐performance liquid chromatography showing a molecular weight of 99.3 kDa. The monosaccharide composition of AGPs were assessed using gas chromatography–mass spectrometry. AGPs were found to be a complex heteropolysaccharide with a repeating unit mainly composed of galactose, arabinose, xylose, mannose, rhamnose, and glucuronic acid with the respective ratios: 45:26:7:10:1:11. The acidic nature of the polysaccharide is due to the presence of glucuronic acid. Total antioxidant activity, free radical‐scavenging activity and reducing power assay of AGPs were investigated. The obtained results showed high antioxidant activities of AGPs. Furthermore, beyond 60 mg mL^?1, AGPs exhibited bacterial growth inhibition for five pathogenic strains: Escherichia coli, Staphylococcus aureus, Enterococcus feacalis, Pseudomonas aeruginosa and Salmonella typhimurium.     

Flow of solutions of hydroxypropyl guar-poly(ethylene oxide) mixtures through a porous medium

Summary In flow through porous media, solutions of poly(ethylene oxide) (PEO) exhibit extension thickening, whereas hydroxypropyl guar (HPG) solutions are shear-thinning at high concentrations. The results show that the extension-thickening exhibited by PEO solutions becomes less critical with increasing flow rate as the concentration of HPG in the solution is increased. At high concentrations of HPG, the presence of PEO inhibits the shear-thinning behaviour, without increasing the apparent viscosity of the solution. The presence of HPG reduces the rate and extent of degradation of PEO in the flowing solution.     

The emulsifying properties of a polysaccharide isolated from the fruit of Cordia abyssinica

Polysaccharide was isolated from Cordia abyssinica and its effect, at differing concentrations, on its emulsifying ability was determined. Emulsions of vegetable oil containing up to 1% of the polysaccharide in phosphate pH 7.4 buffer, were prepared by using a hand piston homogenizer. Emulsification was assessed by diluting samples of the emulsions in sodium dodecyl sulphate and measuring absorbance at 500 nm. Addition of increasing concentrations of the polysaccharide up to 1% enhanced emulsification and emulsion stability. Above 1% concentration the polysaccharide solutions were too viscous for making emulsions conveniently. At a constant concentration of the polysaccharide, addition of up to a 1% concentration of salt enhanced emulsion formation. Further addition of salt above 1% resulted in no further changes in emulsifying ability, but the stability of the emulsions formed decreased on increasing the concentration of salt above 1%. The effect of pH on emulsifying ability was investigated by preparing emulsions using buffers of different pH, from pH 3 to pH 13. The polysaccharide had poor emulsifying ability below pH 7. Emulsifying ability increased with pH between pH 7 and 11. At pH above 11 there was a decrease in emulsifying ability.     

黄原胶接枝共聚物降滤失剂应用性能评价

黄原胶（XG）具有优良的耐盐性和增稠降滤失性能，但耐温性较差。对XG分子结构的分析认为，可利用XG链上的活泼基团接枝丙烯酰胺等乙烯基单体，增强其耐温性能，用作耐温抗盐钻井液处理剂。对比了合成的黄原胶丙烯酰胺等接枝共聚物（XGG）降滤失剂与XG在淡水、4％盐水和饱和盐水钻井液中的增粘降滤失性能和抗温性能，并通过岩心膨胀试验对比了XGG、XG和KCl对页岩的抑制性能。试验结果表明，在淡水钻井液中XGG具有极强的增粘效果和降滤失能力，远远超过XG1随着钻井液矿化度的提高，XGG的性能有一定下降，但XGG在各种钻井液中均具有比XG更好的高温增稠和控制失水的能力；XG已具有优良的抑制性，XGG的抑制性得到进一步提高。     

Potential applications of poly(vinyl alcohol)‐congo red aqueous solutions and hydrogels as liquids for hydraulic fracturing

The authors report on the viscoelastic characterization of guar hydrogels obtained through complexation reactions with borax ions. These gels are compared with hydrogels obtained from poly(vinyl alcohol) of different degree of hydrolysis through complexation reactions with congo red. The effect of the degree of hydrolysis and both, the concentration of PVA and the concentration of congo red, on the viscoelastic properties of the hydrogels is analyzed. The potential use of the PVA‐based hydrogels as hydraulic fracturing liquids is discussed in relation to the commonly used fracturing liquid based on the guar–borax system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

户外像素管软质灌注胶的研制与应用

采用脂环族环氧树脂、柔韧性环氧树脂、改性脂环胺类固化剂为主要原料，研制出户外像素管灌注软胶，产品具有耐紫外线辐照、耐冷热冲击、粘接性好等特点。介绍其制备方法、性能及用。     

新型加成型硅橡胶灌封胶的研究

本文合成了两种新型加成型硅橡胶：ＴＡＳ硅橡胶和ＭＤＡＳ硅橡胶。与通常使用的乙烯基加成型硅橡胶相比，ＴＡＳ或ＭＤＡＳ硅橡胶的固化条件与之相似，但ＴＡＳ－ｐｔ和ＭＤＡＳ－ｐｔ固化体系对许多能阻滞乙烯基加成型硅橡胶固化的物质不敏感。另一方面，ＴＡＳ－ｐｔ和ＭＤＡＳ－ｐｔ固化体系对许多材料（尤其对金属）呈现良好的粘接性能，且当样品浸于水中１５天后，仍保持其粘性。上述性能，使之具有许多用途。本文还讨论了ＴＡＳ和ＭＤＡＳ生胶的合成方法，以及影响ＴＡＳ、ＭＤＡＳ固化的若干因素。     

黄原胶的结构、性能与应用

简要介绍了黄原胶的结构、性能;综述了它在化学工业及食品工业中的应用;重点论述了黄原胶作为悬浮剂、乳化剂、稳定剂、增稠剂等在日用化学工业中的应用,具有优良的悬浮性、乳化性、流变性、热稳定性及酸、碱稳定性;最后指出了我国在黄原胶应用方面的不足及以后的发展方向。     

Studies on graft copolymerization of 4‐vinylpyridine onto guar gum

Graft copolymerization of 4‐vinylpyridine (4‐VP) onto guar gum (GOH) using potassium monopersulfate (PMS)/thioacetamide (TAA) as a redox pair was studied in an aqueous medium under inert atmosphere. The concentration of potassium monopersulfate and thioacetamide should be 1.0 × 10^?2 and 5.0 × 10^?3 mol dm^?3, respectively, for highest grafting ratio and efficiency. Efficient grafting was observed at 19.25 × 10^?2 and 4.87 × 10^?2 mol dm^?3 concentration of 4‐vinylpyridine and sulfuric acid, respectively. The optimum temperature for grafting is 30°C. As the time period of reaction is increased, the grafting ratio increases, whereas efficiency decreases. The plausible mechanism of grafting has been suggested. A sample of guar gum and guar‐ g‐4‐vinylpyridine were subjected to thermogravimetric analysis with the objective of studying the effect of grafting 4‐vinylpyridine on the thermal stability of guar gum. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2380–2385, 2002     

Transport of Gellan Gum Microbeads in Soil Columns of Various Grain Size Distributions

The transport of gellan gum microbeads as potential cell carriers was investigated in horizontal columns packed with different grain size classes of gravel (2–16 mm) and sand (0.25–2 mm). A suspension of microbeads was pulsed into each column for 6 h, followed by injection of water for 42 h. In general, the total amount of microbeads travelling across a given section of the column increased with injection time but decreased towards the column outlet, varying as a direct function of grain size. The results of this study demonstrate the feasibility of the transport of gellan gum microbeads through medium sand to medium gravel across distances up to 110 cm.