共查询到14条相似文献,搜索用时 62 毫秒
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本文探索了表征羟丙基瓜尔胶(HPG)中羟丙基摩尔取代度(MS)以及取代位置的化学方法.当反应温度为110℃、反应时间为14h以及HPG中羟基与对甲苯磺酸-乙酸酐摩尔比为1:3.5时,用对甲苯磺酸-乙酸酐化学法和气相色谱法可准确测定HPG的羟丙基MS,与1H-NMR测定结果相对误差小于10%.在pH=10.30和0℃的条件下,瓜尔胶的伯羟基被2,2,6,6-四甲基哌啶氮--氧化物(TEMPO)-NaClO-NaBr体系选择性氧化成羧基,由此可表征羟丙基链段的取代位置. 相似文献
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高碘酸钠氧化法测定羟丙基瓜尔胶上仲羟基取代度 总被引:1,自引:0,他引:1
高碘酸钠氧化可以使邻羟基C-C键发生高选择性断裂, 同时产生两分子醛基. 在pH=4.3及25 ℃的条件下, 对瓜尔胶及其衍生物羟丙基瓜尔胶进行高碘酸钠氧化, 采用红外光谱与核磁共振谱对氧化产物结构进行了表征. 结果表明, 氧化后的瓜尔胶和及羟丙基瓜尔胶结构中醛基主要以半缩醛的形式存在. 通过测定高碘酸钠的消耗量得到不同摩尔取代度羟丙基瓜尔胶糖单元上邻羟基的含量, 结合概率分析方法, 确定摩尔取代度分别为0.04, 0.14, 0.36, 0.51, 0.78, 1.05和1.53的羟丙基瓜尔胶在仲羟基上取代度分别为0.02, 0.09, 0.18, 0.30, 0.46, 0.59和1.03, 与其它方法得到的结果一致. 相似文献
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本文在研究1,6-脱水葡萄糖均聚的基础上,提出了一种用1,6-脱水葡萄糖对瓜尔胶进行绿色化改性的新方法,并通过核磁对瓜尔胶的葡萄糖接枝产物进行表征,发现随着1,6-脱水葡萄糖与瓜尔胶质量比的增加,产物的葡萄糖摩尔取代度逐渐增大,当1,6-脱水葡萄糖与瓜尔胶质量比为3:1时,共聚产物的摩尔取代度可达0.6.1,6-脱水葡... 相似文献
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本文以离子液体1-烯丙基-3-甲基咪唑氯盐(AmimCl)为反应介质,以氢氧化钠为催化剂合成了羟丙基瓜尔胶(HPG),并通过1H NMR确定了产品的摩尔取代度。探讨了水的用量、环氧丙烷的用量、反应温度和反应时间对摩尔取代度的影响。在水与瓜尔胶的质量比为1.7、氢氧化钠与瓜尔胶的质量比为5%、环氧丙烷与瓜尔胶的质量比为3.5、反应温度为60℃和反应时间为12h的条件下,摩尔取代度(MS)可以达到0.76。同时发现在不加催化剂NaOH的情况下,瓜尔胶在AmimCl中的羟丙基化反应同样可以发生,只是得到的HPG的MS相对较小。 相似文献
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Utilization of raw materials available in nature and their application to derive other useful products without any adverse impact on the environment has long been a desired goal. In this work, guar gum (GG) and attapulgite (APT) clay were used as raw materials for preparing guar gum‐g‐poly(acrylic acid)/attapulgite (GG‐g‐PAA/APT) superabsorbent composites through the graft copolymerization of GG, partially neutralized acrylic acid (AA) and APT in aqueous solution. The effects of reaction conditions such as concentrations of the initiator and crosslinker, APT content, etc. on water absorbency were investigated. The composite prepared under optimal conditions gave the best absorption of 529 g/g sample in distilled water and 61 g/g sample in 0.9 wt% NaCl solution. Swelling behaviors revealed that the superabsorbent composites retained a high water absorbency over a wide pH range of 4–11, and the developed composites also exhibited improved reswelling and water‐retention capabilities. The superabsorbent composites can be utilized as eco‐friendly water‐manageable materials for agricultural and horticultural applications. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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《Journal of Polymer Science.Polymer Physics》2018,56(3):239-247
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 相似文献
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Thermal and mechanical properties of cationic guar gum/poly(acrylic acid) hydrogel membranes 总被引:3,自引:0,他引:3
Yihong Huang 《Polymer Degradation and Stability》2007,92(6):1072-1081
Novel hydrogel membranes (coded as GA) based on cationic guar gum (CGG) and poly(acrylic acid) (PAA) were synthesized with various feed compositions. Their structure and properties were studied by Fourier transform infrared spectra, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analyses and tensile tests. The structure analyses indicated that there existed strong electrostatic interaction between CGG and PAA, which resulted in uniform structure and complete miscibility between the two components. On the basis of thermogravimetric analyses, the activation energies (Ea) of the first degradation of the membranes increased from 34.5 to 77.1 kJ/mol with an increase of CGG content, while the residual ratios of the membranes increased from 7.6 to 36.1 wt% at 600 °C. This indicated an elevated thermal stability of PAA-based materials through an introduction of CGG. The tensile tests exhibited the mechanical properties of the membranes were improved with an increase of CGG content, and the maximum value of 41.1 MPa was reached. 相似文献