Impregnation of thermoplastic resin in jute fiber mat

Impregnation rate of thermoplastic resin (polypropylene) in jute fiber mat and influence of relative factors on impregnation were studied, aiming to develop the continuous melt impregnation technique and to investigate the effect of impregnation rate and temperature on processing conditions and mechanical properties of natural fiber mat-reinforced thermoplastics. Influence of pressure on porosity of fiber mat and effect of melt viscosity on impregnation rate were also investigated. The modified capillary rheometer was used as apparatus and experimental data were analyzed based on the one-dimension Darcy’s law. Results showed that at a given pressure, the impregnation rate is inversely proportional to melt viscosity and jute fiber mat has higher porosity than glass fiber mat. The architecture, compressibility, permeability and fiber diameter of jute fiber mat were compared with those of glass fiber mat and their effects on impregnation were discussed further. It could be seen that the average diameter of jute fiber is much bigger; the porosity of jute fiber mat is significantly higher and inner bundle impregnation does not exist in jute fiber mat. Therefore, it is not difficult to understand why the impregnation rate in jute fiber mat is 3.5 times higher and permeability is 14 times greater. Kozeny constants of jute and glass fiber mats calculated based on the capillary model are 2950 and 442, respectively. __________ Translated from Journal of Chemical Engineering of Chinese Universities, 2007, 21(4): 586–591 [译自: 高校化学工程学报]     

炭黑在两相高分子导电复合材料中选择性分布研究进展

综述了影响炭黑在两相高分子复合材料中选择性分布的因素及炭黑的选择性分布对复合材料电性能的影响,指出了炭黑填充导电高分子复合材料的研究方向。     

PVB边角料用于硬质聚氯乙烯的改性研究

利用汽车夹层玻璃生产中所产生的大量边角料聚乙烯醇缩丁醛(PVB)来改性硬质聚氯乙烯(PVC-U),以提高PVC-U的冲击性能,测试了PVC-U/PVB共混物的冲击性能、拉伸性能及加工性能,并用场发射环境扫描电子显微镜(SEM)对其进行了断面形貌分析.结果表明,当100份PVC-U中加入5份PVB时,PVC-U/PVB体系的相容性较好,其冲击性能是纯PVC-U的2倍以上,而体系的拉伸性能变化不大,同时加工性能也得到了很好的改善.     

炭黑填充复合型导电聚合物的压阻特性

总结了炭黑填充复合型导电聚合物的压阻特性与炭黑导电网络、压力和时间等条件的关系,阐述了加工工艺参数、导电填料、基体性质等对导电聚合物压阻特性的影响,并介绍了通过加入SiO2纳米材料或适当交联基体等改善压阻特性重复性和稳定性的方法.     

鼓泡塔反应器内两相流动态模拟研究

采用双流体模型以及考虑气相影响的湍流模型,对矩形鼓泡反应器中气液两相流行为进行了两维和三维数值模拟.结果表明,两维模拟不能准确预测气液两相流动态行为,而三维数值模拟则能准确模拟两相流动态行为.通过比较湍流粘度,发现两维模拟所得湍流粘度要比三维模拟高一个数量级.比较了三维模拟中湍流模型对模拟结果的影响.发现RNGK-E模型所模拟的气泡流摆动周期明显小于K-E模型的模拟结果,模拟结果更接近实验结果.考察了升力和虚拟质量力在多相流动态行为模拟中的作用,发现它们对模拟结果产生不同程度的影响,其中升力的影响比虚拟质量力的影响显著.     

探讨影响SERES2000高锰酸盐指数分析仪测定结果的主要因素

高锰酸盐指数是一个条件性的相对指标,本文将讨论加热温度、加热时间等反应条件对SERES2000高锰酸盐指数分析仪测定结果的影响。     

Controllable electrode activities of nano-carbon films while maintaining surface flatness by electrochemical pretreatment

A carbon film consisting nanocrystallites with mixed sp² and sp³ bonds formed by using the electron cyclotron resonance (ECR) sputtering method was studied with respect to the changes in characteristics caused by electrochemical pretreatment (ECP). Unlike glassy carbon, our sputtered nanocrystalline carbon film deposited at an acceleration voltage of 75 V (ECR-75 nano-carbon film) largely retained its surface flatness after the ECP. This robust surface could be caused by an increase of 42% in the sp³ carbon realized by increasing the acceleration voltage during sputtering. The electrode activity of ECR-75 nano-carbon film was improved for surface sensitive species including Fe^3+/2+ unlike the boron doped diamond (BDD) electrode. This is because a sufficient quantity of surface sp² bonds remained and because the introduction of surface oxygen-containing groups is more efficient than with the BDD electrode. With pretreated ECR-75 nano-carbon film, the peak potential of glutathione was reduced solely due to the increase in the surface hydrophilicity with a sufficient quantity of surface sp² bonds, thus achieving the lowest detection limit (0.4 μM) ever obtained with carbon electrodes. We also achieved the stable measurement of 30 μM of serotonin (20 times) without the electrode surface fouling found with other electrodes.     

Effect of graphite intercalation compounds in the interfacial zone on the mechanical and thermal properties of unidirectional carbon fiber reinforced spodumene composite

The interface in unidirectional carbon-fiber-reinforced β-spodumene matrix composite (UD-Cf/β-spodumene) significantly affected the thermal conductivity characteristics and mechanical properties due to the presence of a multi-layer interface. The mechanical and thermal properties of UD-Cf/β-spodumene composites with and without a multi-layer interface have been studied. The measured thermal conductivities, flexural strength and fracture toughness of composites with a multi-layer interface were much better than those composites with a clear interface. Interfacial layers with a multi-layer morphology originated from the diffusion of lithium from the β-spodumene matrix to the surface of the carbon fiber, which led to the formation of graphite intercalation compounds. The mechanical properties and thermal conductivity of UD-Cf/β-spodumene hot pressed at 1350 and 1400 °C were enhanced due to the textured interfacial microstructure and high thermal conductivity of graphite intercalation compounds. The textured interface decomposed at 1450 °C, resulting in the formation of a “strong” interface. Inevitably, the mechanical properties and thermal conductivity decreased.     

High nitrogen carbon material with rich defects as a highly efficient metal-free catalyst for excellent catalytic performance of acetylene hydrochlorination

In this work,we developed a simple strategy to synthesize a carbon material with high nitrogen and rich carbon defects.Our approach polymerized diaminopyridine(DAP) and ammonium persulfate(APS).Following a range of different temperature pyrolysis approaches,the resulting rough surface was shown to exhibit edge defects due to N-doping on graphite carbon.A series of catalysts were evaluated using a variety of characterization techniques and tested for catalytic performance.The catalytic performance of the N-doped carbon material enhanced alongside an increment in carbon defects.The NC-800 catalyst exhibited outstanding catalytic activity and stability in acetylene hydrochlorination(C_2 H_2 GHSV=30 h~(-1),at 220℃,the acetylene conversion rate was 98%),with its stability reaching up to 450 h.Due to NC-800 having a nitrogen content of up to 13.46%,it had the largest specific surface area and a high defect amount,as well as strong C_2 H_2 and HCl adsorption.NC-800 has excellent catalytic activity and stability to reflect its unlimited potential as a carbon material.     

Prediction and verification of heat capacities for pure ionic liquids

The heat capacity of ionic liquids is an important physical property,and experimental measuring is usually used as a common method to obtain them.Owing to the huge number of ionic liquids that can be potentially synthesized,it is desirable to acquire theoretical predictions.In this work,the Conductor-like Screening Model for Real Solvents(COSMO-RS) was used to predict the heat capacity of pure ionic liquids,and an intensive literature survey was conducted for providing a database to verify the prediction of COSMO-RS.The survey shows that the heat capacity is available for 117 ionic liquids at temperatures ranging 77.66-520 K since 2004,and the 4025 data points in total with the values from 76.37 to 1484 J·mol~(-1)·K~(-1) have been reported.The prediction of heat capacity with COSMO-RS can only be conducted at two temperatures(298 and 323 K).The comparison with the experimental data proves the prediction reliability of COSMO-RS,and the average relative deviation(ARD) is 8.54%.Based on the predictions at two temperatures,a linear equation was obtained for each ionic liquid,and the heat capacities at other temperatures were then estimated via interpolation and extrapolation.The acquired heat capacities at other temperatures were then compared with the experimental data,and the ARD is only 9.50%.This evidences that the heat capacity of a pure ionic liquid follows a linear equation within the temperature range of study,and COSMO-RS can be used to predict the heat capacity of ionic liquids reliably.