Syntheses and properties of superabsorbent composites based on natural guar gum and attapulgite

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.     

Fe2O3/ATP载氧体制备及煤化学链燃烧性能研究

以天然凹凸棒(ATP)为载体,分别利用机械混合法、浸渍法和溶胶-凝胶法制备了3种铁基复合载氧体。利用X射线衍射(XRD)、能谱(EDS)、N₂-吸附脱附等温线等对其进行物化表征,并在900 ℃流化床中考察其煤化学链燃烧反应性能。结果表明,ATP能显著增加载氧体比表面积和抗磨损能力,并对煤转化过程有催化作用,其与Fe₂O₃的协同作用使初始碳转化速率显著提高。溶胶-凝胶法制备的U-Fe4ATP6表面Ca元素含量为4.3%,比表面积为4.920 7 m²/g,均高于其他两种载氧体,表现出更高的催化性能和反应活性:初始碳转化速率为0.168 min^-1,平均CO₂浓度为98.6%,燃烧效率为98.7%。20次反应后,U-Fe4ATP6催化性能略有降低,对应的初始碳转化速率降至0.108 min^-1,停留时间t₉₅延长到18 min;且能维持较高的反应活性,对应的CO₂捕集效率和燃烧效率分别稳定在98.6%和96.7%。     

Orientation behavior of attapulgite nanoparticles in poly(acrylonitrile)/attapulgite solutions by rheological analysis

Nanocomposites based on poly(acrylonitrile) (PAN) and attapulgite (AT) had been prepared by solution blending in dimethyl sulfoxide (DMSO). The rheological properties of the nanocomposites solutions were investigated by HAAKE rheometer with plate‐cone geometry. The steady and oscillation shear experiments were carried out to investigate the effects of clay exfoliation and orientation as well as polymer‐clay interaction. The presence of small amount of AT nanoparticles with large aspect ratio improved the fluidity of these PAN solutions under low shear rate, whereas large amount of AT will reduce its aspect ratio by aggregation and constrain the polymer segment motion in the solutions. The relaxation and disentanglement behaviors of the PAN chains in nanocomposite solutions were also studied by oscillation and thixotropic experiments, from which, it can be concluded that well dispersed and oriented AT nanorods will reduce interaction among macromolecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 945–954, 2009     

凹凸棒石黏土润滑油添加剂对钢/钢摩擦副摩擦学性能的影响

采用天然凹凸棒石黏土作为润滑油添加剂加入150SN润滑油中,在Optimal SRV-IV摩擦磨损试验机上研究了添加剂含量对钢/钢摩擦副摩擦学性能的影响,借助SEM及EDS分析了摩擦副的表面形貌及表面元素组成.结果表明:凹凸棒石黏土的浓度为0.6%可使平均摩擦系数较基础油润滑条件下降低42.32%;凹凸棒石黏土的浓度为0.4%可使磨损体积降低85.48%;凹凸棒石黏土的加入使得磨损表面更加光滑平整,同时磨损表面氧元素含量升高.分析认为凹凸棒石黏土层链状的晶体结构和摩擦过程中复杂的理化过程是实现减磨抗磨的原因.     

槲皮素表面分子印迹聚合物的制备及其应用研究

以接枝双键的凹凸棒土(TM)为载体,槲皮素为模板分子,采用表面印迹技术制备对槲皮素具有特异吸附性能的分子印迹聚合物(MIP)。利用光谱法选择实验条件及对化合物表征。采用静态法研究聚合物对槲皮素的结合性能与识别性能。结果表明,该分子印迹材料对槲皮素具有特异的识别特性和优良的亲和性,提高了传统聚合物的结合率。以该印迹聚合物为固相萃取材料,结合高效液相色谱法,对白菜中的槲皮素进行分离富集,方法回收率为84.0%~90.6%,相对标准偏差低于5.6%。     

凹凸棒土增强聚丙烯复合材料冲击断裂韧性的研究

 用Charpy冲击实验装置研究凹凸棒土（AT）增强聚丙烯（PP）复合材料的断裂韧性。测量AT含量为10wt%~40wt%试样的断裂韧性。结果显示，在AT含量为10wt%~30wt%范围内，复合材料的断裂韧性（G_c）高于纯基体PP．这说明，在一定条件下，加入AT可以改善PP的断裂韧性。     

STUDY ON THE ADSORPTION BEHAVIOR OF Pb(Ⅱ) ON NANOMETER ATTAPULGITE BY FAAS

The adsorptive behavior of nanometer attapulgite modified by acid to Pb(Ⅱ) was investigated by flame atomic absorption spectrometry (FAAS) in this paper. The mainly effect parameters on the adsorptive efficiency of Pb(Ⅱ), such as the acidity of the solution, the amount of attapulgite, oscillation time and static time were studied. Also the influencing factors of the recovery efficiency of Pb(Ⅱ), including the concentration of hydrochloric acid, the volume of hydrochloric acid, oscillation time and static time were investigated. The adsorptive capacity of Pb(Ⅱ) on nanometer attapulgite was 26.5mg/g and the adsorptive capacity of first cycle and second cycle regenerated nanometer attapulgite were 26.5mg/g and 26.3mg/g, respectively. The results obtained indicated that the regenerated effect was good.     

A Kinetic Study of the Thermal Degradation of Nylon-6/Attapulgite Nanocomposites

The thermal degradation behavior of nylon-6 (PA6) and PA6/attapulgite (ATP) nanocomposites was investigated by thermogravimetric analysis under non-isothermal conditions at various heating rates in nitrogen. It is suggested that during thermal degradation, ATP, as a protective barrier, can slow down degradation of polymer, but the catalytic effects of structural water and hydroxyl groups may accelerate the degradation of PA6. The combination of these two effects determined the final thermal stability of nanocomposites. The apparent activation energies of the samples were evaluated by the Kissinger and Flynn–Wall–Ozawa methods. The results showed that the presence of ATP adversely affected the thermal stability of PA6. The degradation activation energies of PA6/ATP nanocomposites decreased monotonically with increase in ATP content; thus, it is suggested that the ATP has a disadvantageous effect on the thermal stability of PA6.     

凹凸棒土应用于重金属离子吸附剂的研究

以新型无机矿物材料凹凸棒土作为吸附剂处理废水中的重金属离子。通过扫描电镜、红外光谱及等温吸附-脱附曲线对凹凸棒土进行了表征,并阐述了凹凸棒土对重金属离子的可能吸附机理。在室温下,分别将0.05 g凹凸棒土投入初始质量浓度为500 mg.L-1的Cu(Ⅱ)、Cd(Ⅱ)、Ni(Ⅱ)和Cr(Ⅵ)的溶液中,凹凸棒土对上述离子的平衡吸附量分别高达99、56、117、198 mg.g-1。结果表明,用凹凸棒土吸附废水中的重金属离子切实可行、经济有效。     

Attapulgite and ultrasonic oscillation induced crystallization behavior of polypropylene

In this article, the effect of ultrasonic oscillation on the dispersed morphology of attapulgite in polypropylene (PP) and crystallizing kinetics of PP/attapulgite composites prepared through extrusion in the presence and the absence of ultrasonic oscillation were studied. X‐ray diffraction analysis results showed that ultrasonic oscillation did not change attapulgite crystal structure during extrusion in PP/attapulgite composites. On the other hand, scanning electron microscopy and transmission electron microscope photographs indicated that ultrasonic oscillation promoted the dispersion of attapulgite particles in PP matrix. The dispersed morphology of attapulgite and ultrasound oscillation affected the crystalline form, nucleation rate, crystallization temperature, crystallinity, and spherulite size of PP crystals. PP transcrystals were formed on the attapulgite particle surface. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2300–2308, 2007