聚酰亚胺/有机蒙脱土/丁苯橡胶复合材料性能的研究

将聚酰亚胺(PI)与有机蒙脱土(OMMT)混合,制备了PI/OMMT粉状材料;将粉状材料与丁苯胶乳(SBR)混合,制备了颗粒状PI/OMMT/SBR复合材料.SEM照片显示,有机蒙脱土可改善聚酰亚胺与丁苯橡胶的相容性.X射线衍射(XRD)结果表明,聚酰亚胺分子链与丁苯橡胶分子链一起插入有机蒙脱土层间,使层间距变大;有机蒙脱土作为交联点存在.动态力学性能测试结果表明,在频率扫描下,加入PI/OMMT后丁苯橡胶的G′最高,但tanδ较低.     

坝体材料非线性对坝基深层抗滑稳定影响分析

结合亭子口水利枢纽升船机上闸首坝基深层抗滑稳定研究,采用非线性有限元法对坝基软弱夹层及抗滑齿槽受荷破坏过程进行了计算分析。为考证齿槽周边坝体混凝土是否会先于软弱夹层屈服,考虑坝体材料为非线性本构关系,并将计算成果与坝体材料为线性本构关系的结果进行比较,分析认为坝体为非线性材料时计算出来的安全系数较小。计算表明,升船机上闸首在设置抗滑齿槽后,整个坝基系统的安全系数较高,坝基深层抗滑稳定是安全的。     

氧化石墨烯-水性环氧树脂固化剂的制备及性能

以三乙烯四胺（TETA）,氧化石墨烯（GO）,环氧树脂E44、三羟甲基丙烷三缩水甘油醚（TPEG）、甲基聚氧乙烯环氧基醚（MEH）和γ-(2,3-环氧丙氧)丙基三甲氧基硅烷（KH560）为原料,采用原位聚合法首先将TETA与GO球磨分散,使TETA与GO通过共价键相连,然后依次滴加E44、TPEG、MEH和KH560合成氧化石墨烯-水性环氧树脂固化剂（TGO-WPEA）,再与环氧树脂乳液（Epikote-6520）复合制得氧化石墨烯改性水性环氧树脂防腐涂料（TGO-EP）。通过FTIR、XPS和XRD对纳米材料进行结构表征,采用电化学测试和盐雾实验对复合涂层TGO-EP的防腐性能进行了研究。结果表明,固化剂分子通过共价键连接到GO表面,改善了GO在环氧树脂中的分散稳定性和接枝率,提高了TGO-EP复合涂料对腐蚀介质的屏蔽性能。与EP涂层相比,其腐蚀电位从-0.267mV提高到-0.125mV,腐蚀电流密度从5.44×10-8减小到1.09×10-8 A/cm2;EIS测试表明,浸泡20d后,TGO-EP仍具有最高的低频阻抗。     

芝麻素及其衍生物与DNA相互作用的研究

在pH=7.4的生理条件下,采用紫外吸收光谱法、圆二色(CD)光谱法、DNA热变性法及粘度法对芝麻提取物芝麻酚(SL)、芝麻素(SN)及细辛脂素(AN)与小牛胸腺DNA(ctDNA)的相互作用机理进行初步探讨。研究结果显示,ctDNA能使三种化合物在290 nm附近处的紫外吸收峰产生减色效应,且伴随轻微的红移现象,ctDNA浓度越大,减色效应越明显,SL、SN及AN与ctDNA的结合常数大小分别为2.65×10~4、4.91×10~4、7.33×10~4 L/mol;三种化合物均能使ctDNA的正CD带(276 nm)增加,负CD带(246 nm)发生轻微的减小,且浓度越大,谱带变化越明显;三种化合物的存在条件下,ctDNA的熔点分别增加了1.75、2.51和6.63℃,且ctDNA粘度均有所增加。综合光谱学和粘度实验的结果,推断三种化合物与DNA的作用方式均为经典的嵌插方式,且作用强度大小为:ANSNSL。     

Degradation induced by nanostructural evolution of polylactide/clay nanocomposites in the isothermal cold crystallization process

BACKGROUND: The aim of the work presented was to study the nanostructural evolution of clay tactoids during the isothermal cold crystallization of polylactide/clay nanocomposites (PLACNs). An interesting degradation behavior of the polylactide (PLA) matrix, however, was observed simultaneously with nanostructural evolution. The possible mechanisms of degradation and structural evolution are discussed. RESULTS: The evolution of the nanostructure and the degradation were studied online or offline using parallel plate rheometry, X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis. The results showed that the intercalation level of the clay tactoids further increased during cold crystallization, leading to simultaneous degradation of the PLA matrix, which was further confirmed by the marked change of small‐ and large‐amplitude oscillatory shear flow behavior of the PLACNs before and after cold crystallization. CONCLUSION: The increase of the intercalation level of the tactoids is due to the diffuse in movement of the PLA chain segments during cold crystallization. In this case, chain‐end scission occurs more easily, especially for those PLA chains around the loose edge and defect site of the tactoids during crystallization, which results in a simultaneous degradation of the PLA matrix. Hence, both the linear and nonlinear dynamic viscoelastic properties show a remarkable change after cold crystallization. Copyright © 2009 Society of Chemical Industry     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Palladium‐nanoparticle intercalated vermiculite for selective hydrogenation of α,β‐unsaturated aldehydes

Palladium nanoparticles were generated in the interlamellar region of swelling 2:1 type vermiculite clay using an adsorption excess isotherm. An adsorption excess isotherm was constructed for vermiculite after exchanging the exchangeable Na⁺ ions in the interlamellar region using a binary liquid mixture (ethanol:toluene). Based on adsorption excess isotherm, 1% w/w palladium was intercalated into the interlamellar space of vermiculite. The Pd‐intercalated vermiculite was characterized by X‐ray diffraction, transmission electron microscopy and atomic absorption spectroscopy. The 1% w/w Pd‐intercalated vermiculite was tested for its catalytic activity towards selective hydrogenation reactions involving some α,β‐unsaturated carbonyl compounds using a pulse reactor and its catalytic activity was compared with commercial 1% Pd/C. The intercalated catalyst was found to be very selective towards the desired product of unsaturated alcohols. Copyright © 2007 Society of Chemical Industry     

Intercalation of PF6 anion into graphitic carbon with nano pore for dual carbon cell with high capacity

Intercalation property of PF₆⁻ into graphitic carbon was studied for a hybrid capacitor with different ratio of cathode and anode amount. Graphene sheet distance increased with increasing PF₆⁻ intercalation amount and it saturated at 0.4 nm at high applied potential, which is corresponded to stage 2 structure. On the other hand, it was found that nano size pore into graphene sheet was introduced at higher applied potential with 20 times larger anode carbon and this nano porous carbon shows a large capacity for intercalation capacity of 147 mAh g⁻¹. The estimated energy density of the hybrid capacitor using carbon with nano bubble structure was ca. 400 Wh kg⁻¹.     

Effect of organo‐modified layered silicates on flammability performance of high‐density polyethylene/rice husk flour nanocomposite

This research was carried out to investigate on the effect of organomodified montmorillonite (OMMT) on the flame retarding characteristics and clay dispersion of composites based on high‐density polyethylene and rice husk flour. To meet this objective, the blend nanocomposites were prepared through the melt mixing of high‐density polyethylene and rice husk flour at 50% weight ratios, with various amounts of OMMT (0, 2, 4, and 6 per hundred compounds) in Hakee internal mixer; then, the samples were made by injection molding. Results indicated that the burning rate, total smoke production, and heat release rate of samples decreased with increasing the OMMT content. Also, the char residue and time to ignition increased with increasing the nanoclay loading. X‐ray diffraction patterns revealed that the nanocomposites formed were intercalated. Also, morphological findings showed that samples containing 2 per hundred compounds of OMMT had higher order of intercalation and better dispersion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011