Flexible Use of Single‐Screw Extruders through Multiple‐Process Optimization

Using general‐purpose screws to process different types of material offers considerable cost advantages over special‐purpose screws. Designing screws of this type is generally a difficult task, since modifications to different aspects of the geometry can run counter to each other in some cases. Optimization software is thus of particular benefit here. For this reason, a program was developed for the optimization of general‐purpose screws. A central feature of this program is an appraisal system for the computer‐aided evaluation of single‐screw simulations. The performance of the software was verified on the basis of actual extrusion experiments.

Temperature measuring cross for measuring thermal homogeneity.     

Samarium Powder‐Catalyzed Palladium‐Free and Ligand‐Free Sonogashira Coupling Reactions

A study of samarium powder‐catalyzed cross‐coupling reactions of aryl halides with terminal alkynes is described. The couplings performed in the polyethylene glycol PEG‐600 provided the corresponding coupling products in good yields. The first example of palladium‐free, copper‐free and amine‐free catalytic system for Sonogashira couplings is presented in the absence of ligand.     

Single‐walled nanotube bucky paper and nanocomposite

A new processing method for the fabrication of single‐walled nanotube (SWNT)‐reinforced nanocomposites was developed to achieve uniform dispersion and high composition of the nanotubes in the nanocomposites. In this method, SWNTs were preformed as bucky paper by multi‐step dispersion and micro‐filtration of a suspension of nanotubes. The nanocomposites were then fabricated by infiltration of diluted epoxy resin through the bucky paper and hot pressing. The wetting of the nanocomposites was examined using scanning electron microscopy and atomic force microscopy. The results showed that the epoxy resin completely penetrated the bucky paper through the nanoporous structures. The results of dynamic mechanical analysis of the nanocomposites showed that the storage moduli of the nanocomposites increased by 200–250%. The tan δ curves indicated that the nanotubes had a strong influence on the damping properties of the nanocomposites. This processing technique is an effective method for fabricating nanocomposites with uniform dispersion and high composition of SWNTs. Copyright © 2006 Society of Chemical Industry     

Potassium–Sodium Niobate‐Based Lead‐Free Piezoelectric Ceramic Coatings by Thermal Spray Process

Potassium–sodium niobate (KNN)‐based piezoelectric ceramic coatings with single perovskite phase and dense morphology were obtained by thermal spray processing. The structure, morphology, and properties of the coatings deposited at different conditions were investigated, and excellent piezoelectric performance properties were demonstrated. The piezoelectric coefficient observed in the KNN‐based coatings in this study is about one order of magnitude higher than other thermal sprayed lead‐free piezoelectric coatings as reported in literature. With analyses on the differences in the characteristics between KNN and lead zirconate titanate (PZT) compositions and the reaction mechanisms of thermal spray and ceramic synthesis, the reasons for the successful formation of single‐phase perovskite structure with high crystallinity in the thermal sprayed KNN‐based coatings while not in PZT are explained.     

Metal‐Free and Copper‐Promoted Single‐Pot Hydrocarboxylation of Cycloalkanes to Carboxylic Acids in Aqueous Medium

A simple and effective method for the transformation, under mild conditions and in aqueous medium, of various cycloalkanes (cyclopentane, cyclohexane, methylcyclohexane, cis‐ and trans‐1,2‐dimethylcyclohexane, cycloheptane, cyclooctane and adamantane) into the corresponding cycloalkanecarboxylic acids bearing one more carbon atom, is achieved. This method is characterized by a single‐pot, low‐temperature hydrocarboxylation reaction of the cycloalkane with carbon monoxide, water and potassium peroxodisulfate in water/acetonitrile medium, proceeding either in the absence or in the presence of a metal promoter. The influence of various reaction parameters, such as type and amount of metal promoter, solvent composition, temperature, time, carbon monoxide pressure, oxidant and cycloalkane, is investigated, leading to an optimization of the cyclohexane and cyclopentane carboxylations. The highest efficiency is observed in the systems promoted by a tetracopper(II) triethanolaminate‐derived complex, which also shows different bond and stereoselectivity parameters (compared to the metal‐free systems) in the carboxylations of methylcyclohexane and stereoisomeric 1,2‐dimethylcyclohexanes. A free radical mechanism is proposed for the carboxylation of cyclohexane as a model substrate, involving the formation of an acyl radical, its oxidation and consequent hydroxylation by water. Relevant features of the present hydrocarboxylation method, besides the operation in aqueous medium, include the exceptional metal‐free and acid‐solvent‐free reaction conditions, a rare hydroxylating role of water, substrate versatility, low temperatures (ca. 50 °C) and a rather high efficiency (up to 72% carboxylic acid yields based on cycloalkane).     

From PET Nanofibrils to Nanofibrillar Single‐Polymer Composites

The preparation of nanofibrillar composite (NFC) materials using single‐polymer nanofibrils as starting materials is described. Such a possibility is offered by (i) the concept of polymer/polymer NFCs, which have recently been manufactured and represent a further development in the field of microfibril‐reinforced composites, and (ii) the opportunity to isolate neat nanofibrils through selective dissolving of the second blend component. The resulting nanofibrillar single‐polymer composites are characterized by superior mechanical properties (the tensile modulus and strength are improved up to 350%), competing with glass‐fiber‐reinforced PET.

     

Transition Metal‐Free Regioselective C‐3 Amidation of Indoles with N‐Fluorobenzenesulfonimide

A direct transition metal‐free regioselective C‐3 amidation of indoles has been developed with the commercially available N‐fluorobenzenesulfonimide (NFSI) as the amino source under external oxidant‐free conditions. This amidation requires only a catalytic amount of base and exhibits excellent functional group tolerance and regioselectivity. The C‐3 regioselectivity was proposed to realize by a free radical mechanism.

     

Ligand‐Free Copper‐Catalyzed Amination of Heteroaryl Halides with Alkyl‐ and Arylamines

N‐Heteroarylations of alkyl‐ and arylamines with various heteroaryl halides have been achieved by ligand‐free copper‐catalyzed cross‐couplings affording aminopyridines and aminopyrimidines in moderate to high yields (up to 99% yield).     

Catalyst‐Free Aldol Additions of 1,3‐Dicarbonyl Compounds

Solvent‐ and catalyst‐free aldol additions of activated aldehydes to 1,3‐dicarbonyl compounds are described. Aldol condensation was not observed under these reaction conditions. This unexpected aldol reaction could be extended successfully to a variety of acyclic and cyclic β‐dicarbonyl compounds.     

Synthesis and Properties of Hydrogen‐Free Detonation Diamond

Detonation‐prepared nanocrystalline diamond powders usually contain hydrogen. Herein, the synthesis of practically hydrogen‐free nanodiamond particles by detonation of benzotrifuroxan (BTF) and their comprehensive characterization by elemental analysis, X‐ray diffraction, electron microscopy, DSC/TGA, and BTE specific‐surface determination is described. The effects of the porosity of BTF and of various neutral or carbonic admixtures to the explosive on the reaction thermodynamics as well as the yield and properties of the product were explored theoretically and experimentally. Hydrogen contamination of nanodiamond was investigated using solid‐state NMR spectroscopy and possible sources of hydrogen explored. Admixing hygroscopic solids to the explosive introduced 0.1 to 0.6 % of hydrogen, as did purification in acidic (rather than neutral) media.     

Revamping Dimethyl Ether Separation to a Single‐Step Process

Process intensification techniques were recently proposed to improve the eco‐efficiency of the conventional dimethyl ether (DME) purification and methanol recovery distillation sequence, but they all require new specific equipment and hence rather high investment costs leading to several years of payback time. However, the alternative of reusing the existing equipment to revamp the two distillation columns of the downstream processing section into a single‐step separation was so far overlooked in the open literature. To solve the problem of costly DME separation, a novel single‐step DME separation taking place in a dividing‐wall column (DWC) is proposed that effectively integrates in one shell the tasks of DME purification and methanol recovery. The new process is optimized in terms of minimal energy requirements, taking into account the restrictions caused by reusing one distillation column like, such as limited diameter or reboiler/condenser heat duty. The results demonstrate that the DWC alternative is feasible and has better performances as compared to the classic sequence, i.e., 28 % lower operating costs and 20 % less capital investment.     

Single‐constant simplification of Kubelka‐Munk turbid‐media theory for paint systems—A review

For opaque coloration systems, Kubelka‐Munk turbid media theory is used commonly to model optical mixing behavior. Most educational publications on the subject use opaque paint systems when describing the two‐constant approach and textile systems when describing the single‐constant simplification. Because of the differences in defining concentration for these systems and the corresponding degrees of freedom, the single‐constant simplification for paint and textile systems are not identical. The second edition of “Principles of Color Technology” showed a numerical example for an opaque paint system modeled using the textile equations. The third edition used the same example but modified the degrees of freedom, a hybrid of the paint and textile approaches. Recent research by Berns and Mohammadi has evaluated the single‐constant simplification for modeling artist paints; they have used both the hybrid and paint approaches. Thus, it was of interest to review these different approaches and determine whether these differences have practical importance and whether future printings and editions of Principles of Color Technology should be modified. The three approaches were tested for tints made from a mixture of cobalt blue and titanium white acrylic emulsion artist paints. The differences between the textile and hybrid approaches were inconsequential. The paint approach was superior and its use is recommended for opaque paint systems. The differences in the numerical example from Principles of Color Technology were very small. For future printings of the third edition, the example will remain unchanged. For future editions, including the numerical example remains an open question. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 201–207, 2007     

Chlorine‐Free Synthesis of Organic Alkyl Carbonates and Five‐ and Six‐Membered Cyclic Carbonates

This report presents a new, one‐pot, facile, selective and green method for methoxycarbonylation of alcohols and synthesis of five‐ and six‐membered cyclic carbonates from corresponding alcohols with dimethyl carbonate (DMC) in the presence of molecular sieves without any additional solvent and catalyst. Syntheses of bifunctional structures comprising a six‐membered cyclic carbonate with allyl ether and methacrylate groups, respectively, for different polymerization modes, were also achieved and showed reproducibility on up‐scaling the processes.