Dependence of flow behaviour on carbon black distribution in polyblend systems

The flow behaviour of four blend systems was determined at four shear rates and three processing temperatures using an extrusion rheometer. The blends were based on natural rubber/polybutadiene elastomers and were prepared using various mixing sequences with the carbon black being added in different ways.The degree of die swelling was found to depend on the blending technique, the processing temperature and the extrusion rate. A theoretical model was used to calculate the stored elastic energy, shear modulus and relaxation time. Melt fracture was observed when the carbon black was premixed in just one component of the blend.     

多元混合燃料一次引爆实验研究

为了提高多元混合燃料的爆炸威力，采用光测和电测方法，进行了小药量无约束空间三组元固态混合燃料的野外一次引爆实验，得到了该装置条件下较优的燃料配比．实验结果表明，该多元固态混合燃料的云雾分散效果明显优于相同质量的TNT，其爆炸场超压呈衰减-增长-再衰减的变化规律，且具有非常相似的压力场分布、适当增加弹体密度可增强这种固态燃料混合物的爆炸威力。     

A specific slit die rheometer for extruded starchy products. Design,validation and application to maize starch

A novel in-line rheometer, called Rheopac, has been designed and built in order to study the rheological behaviour of starchy products or, more generally, of products sensitive to a thermomechanical treatment. It is based on the principle of a twin channel, using a balance of feed rate between each of them, in order to make local shear rate vary in the measuring section without changing the flow conditions into the extruder. A wide range of shear rate could be reached and measurements were performed more swiftly than with a classical slit die. The viscous behaviour of maize starch was studied by taking into account the influence of the thermomechanical history, which modified the starch degradation and thus led to important variations in the viscosity. Experimental results were satisfactorily compared to previously published models.Nomenclature E activation energy (J · mol^–1) - h channel depth (m) - h ₁ depth under the piston valve in channel 1 (m) - h ₂ depth under the piston valve in channel 2 (m) - K consistency (Pa·s ⁿ ) - K ₀ reference consistency (Pa·s ⁿ ) - L total channel length (m) - L _p length of the piston valve (m) - MC moisture content (wet basis) - n power law index - N screw rotation speed (rpm) - P ₀ entrance pressure (Pa) - P _e pressure at the entry of the piston valve (Pa) - Q ₁ flow rate in channel 1 (m3 · s^–1) - Q ₂ flow rate in channel 2 m³·s^–1) - Q _T total flow rate (m3 · s^–1) - R constant of perfect gas (8.314 J·mol^–1·K^–1) - SME specific mechanical energy (kWh · t^–1) - T temperature (°C) - T _a absolute temperature (K) - T _b barrel temperature (°C) - T _d die temperature (°C) - T _p product temperature (°C) - w channel width (m) - W energetical term (J·m^–3) - viscosity (Pa · s) - [gh ₀] intrinsic viscosity of native starch (ml·g^–1) - [] intrinsic viscosity (ml·g^–1) - shear rate (s^–1) - shear rate in measuring section (s^–1) - maximum shear rate (s^–1)     

Immobilization of 1,4-Diazabicyclo[2.2.2]Octane (DABCO) over Mesoporous Silica SBA-15: An Efficient Approach for the Synthesis of Functionalized Spirochromenes

Immobilized 1,4-diazabicyclo[2.2.2]octane (DABCO) over mesoporous silica SBA-15 has been found to be an efficient heterogeneous base catalyst for the synthesis of biologically active functionalized spirochromene derivatives via three-component reaction of isatins/acenaphthoquinone, activated methylene reagents, and 1,3-dicarbonyl compounds in aqueous media. This ecofriendly protocol offers several advantages such as a cost-effective procedure with excellent yield, short reaction time, simple workup, recovery and reusability of catalyst, good functional group tolerance, and broad scope of usable substrates.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Recent Advances in One-Pot Modular Synthesis of 2-Quinolones

It is known that 2-quinolones are broadly applicable chemical structures in medicinal and agrochemical research as well as various functional materials. A number of current publications about their synthesis and their applications emphasize the importance of these small molecules. The early synthetic chemistry originated from the same principle of the classical Friedländer and Knorr procedures for the preparation of quinolines. The analogous processes were developed by applying new synthetic tools such as novel catalysts, the microwave irradiation method, etc., whereas recent innovations in new bond forming reactions have allowed for novel strategies to construct the core structures of 2-quinolones beyond the bond disconnections based on two classical reactions. Over the last few decades, some reviews on structure-based, catalyst-based, and bioactivity-based studies have been released. In this focused review, we extensively surveyed recent examples of one-pot reactions, particularly in view of modular approaches. Thus, the contents are categorized as three major sections (two-, three-, and four-component reactions) according to the number of reagents that ultimately compose atoms of the core structures of 2-quinolones. The collected synthetic methods are discussed from the perspectives of strategy, efficiency, selectivity, and reaction mechanism.     

Visible Light-Induced Synthesis of 2-Oxazolidinones through One-Pot Coupling of Benzylamines,Epoxides and CO2

The synthesis of 2-oxazolidinones from a three component coupling reaction of amines, epoxides, and CO₂. The reaction proceeds in the presence of 1,1,3,3-tetramethylguanidine under visible light irradiation at atmospheric pressure. The optimized structures of all species involved in the reaction mechanism along with transition states have been described based on the DFT calculations. The developed methodology represents a promising approach of employing CO₂ as a naturally abundant and non-toxic carbon resource to produce profitable chemicals.     

A STOICHIOMETRIC DISPLACEMENT MODEL FOR RETENTION OF SOLUTE IN LIQUID CHROMATOGRAPHY WITH MULTI-COMPONENT SYSTEM

Considering all the kinds of interactions between solute and solvent, solute and stationary phase, solvent and stationary phase molecules as well as the competitional adsorption among various kinds of solvent molecules on the stationary phase, we present a stoichiometric displacement model of solute retention with four sets of parameters in liquid chromatography. This model was tested with data from both literature and experiments done by ourselves. These results show that this model may fit the experimental data for a liquid chromatography system with various kinds of mobile phases consisting of a complete range of multi-components and with different types of stationary phases.     

变形-损伤耦合的起塑性恒压轴对称充模胀形的有限元模拟

采用大变形刚粘塑性有限元法模拟超塑性恒压轴对称充模胀形过程、分析了模具几何参数及材料参数对胀形过程中材料的流变行为、胀形制许厚度分布和成形时间的影响规律。给出了质点的流动轨迹、不同时刻制件的剖面形状及应力、应变分布；基于修正的Gurson粘塑性势推导了内部空洞体积分数累积增大模型并据此进行了变形-损伤耦合计算．