The Competition Kinetics of Unbranched Chain Processes of Free-Radical Addition to Double Bonds of Molecules with the Formation of 1:1 Adducts

Abstract

Based on a kinetic model involving competing parallel reactions for free-radical addition to the double bond of a molecule with the formation of 1:1 adduct and participation of three radical types in the chain propagation, versions of the rate equation with 1 - 3 measurable parameters are derived. These versions make it possible to describe the nonmonotonic (with maximum) dependence of the formation rate of an addition product on concentration of the unsaturated compound. The unbranched chain process occurs in binary liquid systems comprising saturated and unsaturated components at comparable concentrations. Application of the competition kinetics of free-radical addition to oxidation of some hydrocarbons is discussed when the reaction that competes with chain propagation reactions involving the alkylperoxy radical RO₂ gives the cyclic alkylhydrotetraoxy radical [R(_?H)O₄H] as a less reactive radical inhibiting the chain process of formation of the main products of oxidation.     

Chemical Modification of Fiber-forming Polymers Based on Recombination Addition Reactions

Abstract

The essence of chemical modification processes of fiber-forming polymers based on recombination addition reactions involves preliminary sorption of low-molecular components by the fiber being in a high elasticity state with the subsequent transfer of interacting substances into a free radical state as a result of chemical or radiation initiation. Recombination of activated parts then leads to the fixation of a low-molecular component in a polymer matrix.

Various versions of these reactions based on modifications of fibrillar proteins (fibroin and keratin). polyamides. cellulose and its esters, polyvinyl alcohol with ionogenic (cationic and anionic) and non-ionogenic (disperse) dyes of different classes have been considered.     

Consumer Attention to an Over‐the‐counter Warning in Four Different Styles of Design

The study consisted of three objectives: (a) to test the relative prominence and conspicuousness of a warning required by US law to be conspicuous; (b) to explore whether or not the conspicuousness of the said warning can be enhanced graphically; and (c) to develop preliminary data for power analysis that would guide decisions related to sample size in future studies. Seventeen subjects viewed four over‐the‐counter drug packages (each with a different style of warning) along with five other products while wearing an eye tracking device. Four styles of warning were used on the over‐the‐counter drug packages: no outline and no fill, outline and no fill, no outline and fill, and outline and fill. The surface area and the placement of the warnings were held constant across all four designs and were consistent with those on commercially available products. Collected data were broken into five zones: warning, brand name, strength, product benefit and net weight. Despite the fact that US law requires it to be conspicuous, the tested warning was significantly less noticeable than the brand name (objective one) for all dependent variables analyzed (α = 0.05). No significant difference was indicated for the varied warning designs (objective two). This could be because not much can be done to enhance prominence when constrained to the limited space that is typically used for such warnings or because of the limited sample size. Power calculations suggest that a sample size of nearly 200 subjects would be required to detect a 2.5 s mean difference at 80% confidence (objective three). Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of Al addition on the phase transformation and interfacial evolution in multilayer Ti-B4C composite

The fully-dense multilayer Ti-B₄C composite doped with 6 wt% Al was fabricated via tape-casting and hot-pressing sintering at 1800 °C and under a uniaxial pressure of 30 MPa for 60 min. The effects of Al addition on the phase composition, interfacial microstructure and fracture toughness of the laminate composite were investigated. Based on the results of WDS and EDS, Al addition was proved to be effective on accelerating atom diffusion between Ti and B₄C due to the melting pool around interface where liquid Al enriched, besides, it helps to transform the interfacial bonding method of physical to metallurgical. Finally, the improvement on toughness of Al doped composite can be attributed to the strong metallurgical bonding and hybrid fracture mode of interface. Our study may provide a potential method for producing high strength and toughness multilayer metal/ceramic composites.     

Effect of SnO–P2O5–MgO glass addition on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-type structured compounds Li_1+xM_xTi_2-x(PO₄)₃ (M = Al, Fe, Y, etc.) have captured much attention due to their air stability, wide electrochemical window and high lithium ion conductivity. Especially, Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a potential solid electrolyte due to its high ionic conductivity. However, its actual density usually has a certain gap with the theoretical density, leading the poor ionic conductivity of LATP. Herein, LATP solid electrolyte with series of SnO–P₂O₅–MgO (SPM, 0.4 wt%, 0.7 wt%, 1.0 wt%, 1.3 wt%) glass addition was successfully synthesized to improve the density and ionic conductivity. The SPM addition change Al/Ti–O bond and P–O bond distances, leading to gradual shrinkage of octahedral AlO₆ and tetrahedral PO₄. The bulk conductivity of the samples increases gradually with SPM glass addition from 0.4 wt% to 1.3 wt%. Both SPM and the second-phase LiTiPO₅, caused by glass addition, are conducive to the improvement of compactness. The relative density of LATP samples increases first from 0 wt% to 0.7 wt%, and then decreases from 0.7 wt% to 1.3 wt% with SPM glass addition. The grain boundary conductivity also changes accordingly. Especially, the highest ionic conductivity of 2.45 × 10^?4 S cm^?1, and a relative density of 96.72% with a low activation energy of 0.34 eV is obtained in LATP with 0.7 wt% SPM. Increasing the density of LATP solid electrolyte is crucial to improve the ionic conductivity of electrolytes and SPM glass addition can promote the development of dense oxide ceramic electrolytes.     

Green chemistry: microwave-assisted facile synthesis of 6-imino-1,3,4-thiadiazenes from reaction of thiocarbohydrazones with malononitrile dimer

The reactions of thiocarbohydrazones with malononitrile dimer under microwave irradiation are reported. These reactions give 6-imino-1,3,4-thiadiazines in good yields. The structures of products were elucidated by MS, IR and NMR spectra together with elemental analyses. The reaction mechanism was discussed.     

An in-depth investigation on the formation of nanoporous silica microspheres in diluted dodecylamine solutions

The morphology and textural characteristics of silica products formed via the hydrolysis and condensation of tetraethyl orthosilicate in increasing diluted dodecylamine solutions have been investigated. The results show that the pH values of the synthesis media increase with the initial additions of water. The formation of silica speeds up as the solution is diluted. As a result, microporous silica microspheres with increasing surface areas, pore volumes, pore and particle sizes are formed by a monomer addition mechanism. Further increases in the amount of water result in the decrease of the concentrations of OH^?. Consequently, the formed silica seeds become less active and the diffusion of silica species is accelerated. The monomer addition process thus becomes difficult. The self-nucleation of silica species leads to the formation of large quantities of primary silica nano particles. In order to minimise the internal energy of the reaction system, the nanoparticles aggregate to form micrometre-sized silica microspheres with a relatively loose structure. The synthesised microspheres can be used in the removal of organic pollutants in water. It is shown that the nanoporous silica microspheres formed by the aggregation mechanism have a faster dye adsorption rate and a higher adsorption capacity than those formed by the monomer addition mechanism.     

CuBr2‐induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin‐film counter electrodes for high‐efficiency dye‐sensitized solar cells

Nanocolloidal polypyrrole (PPy):poly(styrene sulfonate) (PSS) particles were synthesized by chemical oxidative polymerization using 15 wt% of PSS. The highly processable polymer composite (PPy:PSS) was spin‐coated at 4000 rpm on fluorine‐doped tin oxide glass and subsequently employed as a counter electrode (CE) for dye‐sensitized solar cells (DSCs). PPy:PSS multilayer (one, three, five) CEs were treated with CuBr₂ salt, which enhances the efficiency of the DSCs. Optical studies reveal that a bulkier counterion hinders interchain interactions of PPy which on salt treatment shows a moderate redshift in absorption maxima. Salt‐treated PPy:PSS films exhibit lower charge transfer resistance, higher surface roughness and better catalytic performance for the reduction of I₃^?, when compared with untreated films. The improved catalytic performance of salt‐treated PPy:PSS multilayer films is attributed to charge screening and conformational change of PPy, along with the removal of excess PSS. Under standard AM 1.5 sunlight illumination, salt treatment is shown to boost the efficiency of multilayer PPy:PSS composite film‐based DSCs, leading to enhanced power conversion efficiency of 6.18, 6.33 and 6.37% for one, three and five layers, respectively. These values are significantly higher (ca 50%) than those for corresponding devices without CuBr₂ salt treatment (3.48, 2.90 and 2.01%, respectively). © 2016 Society of Chemical Industry     

S7-200PLC在除湿机控制系统中的应用

采用西门子S7-200 PLC为主控制器,配以人机界面TD400C和通信模块EM277,设计了某除湿机控制系统.温度、湿度的采集采用频率输出方式的传感器/变送器,将频率信号接入PLC集成的高速脉冲输入口,定时计数从而得到采样值.控制指令可以从数字输入接口、TD400C或上层计算机获得;系统运行状态也可在数字输出接口、TD400C上显示或传送至上层计算机.