Influence of Preparation Conditions on Properties of a Copper-Containing Catalyst for Electrocatalytic Oxidation of Acetone

Stages of synthesis of a copper-containing catalyst for electrocatalytic oxidation of acetone in waste gases were studied. The course of the extrusion and calcination and their influence on electrocatalytic oxidation of acetone on the catalyst synthesized were analyzed.     

Influence of repeated processing on the change in properties of polypropylene

The problems associated with the repeated extrusion of polypropylene and the changes in properties induced by this treatment have been studied Rheological properties of the melt; namely, the course of the flow curves and the growth of the profiles on the discharge side of the extrusion die, have been evaluated. The consequences of repeated extrusion are further projected into the processes of weathering and accelerated ageing, measured on the basis of the changes of the mechanical properties, the limiting viscosity number and the oxidation of the polymer.     

X-ray photoelectron spectroscopy studies of polyethylene-aluminium laminates

X-ray photoelectron spectroscopy was used to examine the effects of extrusion temperature, antioxidants and ozone pre-treatment on the oxidation of polyethylene. The oxidation levels are related to the adhesion between polyethylene and aluminium. The relevance of weak boundary layers is discussed.     

Rapid access to pyrimido[5,4-c]isoquinolines via a sulfur monoxide extrusion reaction

The scope of a sulfur monoxide extrusion reaction of pyrimido[4,5-b][1,4]benzothiazepines leading to pyrimido[5,4-c]isoquinolines was investigated. Thus, selective oxidation followed by nucleophilic displacement of the oxidized side chain sulfur group and subsequent extrusion reaction of sulfur monoxide in the ring, which can be conducted in a two-step sequence or in a one-pot procedure, produced novel pyrimido[5,4-c]isoquinolines, a class of compounds with potential biological and pharmaceutical applications. [reaction: see text].     

Thermal oxidation and molding feasibility of cycloolefin copolymers (COCs) with high glass transition temperature

Cycloolefin copolymers (COCs) with high glass transition temperature (T_g = 203 °C) have been synthesized and pelletized by extrusion molding. However, their colors change from transparent to yellow during extrusion molding because of thermal oxidation and generation of alkene groups. We have successfully blended several antioxidants (Irganox 1010, Irgafos 168, Irganox HP2225 and Irganox HP2921) into lab-made COCs to avoid the discoloration. The experimental results show that Irganox HP2921 is the best antioxidant among the antioxidants used and can effectively not only suppress thermal oxidation but also eliminate the color stain.     

A torquoselective extrusion of isoxazoline N-oxides. Application to the synthesis of aryl vinyl and divinyl ketones for Nazarov cyclization

A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones.     

Intermediacy of bicyclo[2.2.1]hepteneone in the photolysis of bicyclo[2.2.2]octenediones

UV Irradiation of cyclohexane solution of bicyclo[2.2.2]octenediones led to facile extrusion of carbon monoxide to give substituted dihydrobiphenyls along with the dehydrogenated products. The inseparable mixtures on DDQ oxidation afforded the biphenyl derivatives. Isolation of an intermediate arising from the initial monodecarbonylation lends support to a proposed mechanistic rationalization.     

Aqueous Oxidation of Sulfonamide Antibiotics: Aromatic Nucleophilic Substitution of an Aniline Radical Cation

Sulfonamide antibiotics are an important class of organic micropollutants in the aquatic environment. For several, sulfur dioxide extrusion products have been previously reported upon photochemical or dark oxidation. Using quantum chemical modeling calculations and transient absorption spectroscopy, it is shown that single‐electron oxidation from sulfadiazine produces the corresponding aniline radical cation. Density functional theory calculations indicate that this intermediate can exist in four protonation states. One species exhibits a low barrier for an intramolecular nucleophilic attack at the para position of the oxidized aniline ring, in which a pyrimidine nitrogen acts as a nucleophile. This attack can lead to a rearranged structure, which exhibits the same connectivity as the SO₂‐extruded oxidation product that was previously observed in the aquatic environment and characterized by NMR spectroscopy. We report a detailed reaction mechanism for this intramolecular aromatic nucleophilic substitution, and we discuss the possibility of this reaction pathway for other sulfonamide drugs.     

Synthesis of a new type of quadruply ortho-bridged biphenyl compounds with disulfide linkage, and its sulfur extrusion in concentrated H2SO4 and photochemical condition

A new methanodithiomethano-bridged dibenzotrithionin (1) has been synthesized. The electrochemical oxidation of 1 and its analogous compound was studied by cyclic voltammetry. A new type of the sulfur extrusion of 1 was found in the reaction of 1 with concd H₂SO₄ or 2 equiv of NOPF₆ and in its photochemical reaction.     

Effect of AlSiFe on the anodizing process of 6063 aluminum

AlSiFe phase can form microscopic galvanic couples that decrease corrosion resistance of 6063 aluminum which may influence the anodizing process. Two samples of 6063 aluminum were prepared. One sample was cut along the extrusion direction of the billet, and the other was cut perpendicular to the extrusion direction. Both samples exhibited the same characteristics, except for the distribution of the second phase AlSiFe. Both samples were subjected to anodizing treatments. Comparison between anodic oxide films was performed. The microstructure of Al substrates and anodic oxide films were examined using a scanning electron microscope, an optical microscope, and a glow discharge optical emission spectrometer. Results indicated that the thicknesses and elemental distributions of the anodic oxide films were almost the same. Moreover, the second phase AlSiFe influenced the anodic oxidation process, resulting in cavities in the anodic oxide film that affected its brightness. Copyright © 2016 John Wiley & Sons, Ltd.     

Reduction of Na+ within a {Mg2Na2} Assembly

Ionic compounds containing sodium cations are notable for their stability and resistance to redox reactivity unless highly reducing electrical potentials are applied. Here we report that treatment of a low oxidation state {Mg₂Na₂} species with non-reducible organic bases induces the spontaneous and completely selective extrusion of sodium metal and oxidation of the Mg^I centers to the more conventional Mg^II state. Although these processes are also characterized by a structural reorganisation of the initially chelated diamide spectator ligand, computational quantum chemical studies indicate that intramolecular electron transfer is abetted by the frontier molecular orbitals (HOMO/LUMO) of the {Mg₂Na₂} ensemble, which arise exclusively from the 3s valence atomic orbitals of the constituent sodium and magnesium atoms.     

Solid-phase oxidation of 2,4-Di-tert-butylphenol and 3,6-Di-tert-butylpyrocatechol in the presence of alkali and alkaline earth metal halides under elastic deformation

Solid-phase oxidation of 2,4-di-tert-butylphenol to give 2,2′,4,4′-tert-butyl-6,6′-bisphenol and of 3,6-di-tert-butylpyrocatechol to afford 3,6-di-tert-butyl-l,2-benzoquinone was performed in the presence of alkali and alkaline earth metals halides under conditions of modified extrusion. The formation of the corresponding metal 3,6-di-tert-butylsemiquinolates was registered by ESR method. The different behavior of chlorides, bromides, and iodides was observed and rationalized basing on the dissimilar complexing ability of halogens. The mechanism of activated oxidation was assumed. The study was carried out under financial support of the Russian Foundation for Basic Research (grant no. 96-03-33253a). Deceased.     

Hydrostatic Extrusion of Poly(L-Lactide)

Poly-L-Lactide(PLLA) has been used as a bone fracture fixation material for several years. However, its mechanical properties are still not satisfied. To improve its mechanical properties, we examined the hydrostatic extrusion procedure on the PLLA rods made by Injection Molding process. The extrusion ratio was adjusted to 3, 6, 9, and 12. The molecular weight of the PLLA decreased from 260,000 to 200,000 after injection molding process, but it did not change during the hydrostatic extrusion procedure. The melting point of PLLA hydrostatic extrusion products were increased with the extrusion ratio, but the increment was not obviouse. Extrusion products having low extrusion ratio had α-form crystal in them, extrusion products having high extrusion ratio had both of α and β-form crystall in them. At extrusion temperature of 145°C, PLLA rods showed the best flowing trends in the pressure medium of PEG 400. Extrusion temperature is placed in the range of crystalline transition temperature and melting point of PLLA. At extrusion ratio 9∼12, the extrusion products showed the best mechanical properties. The highest bending strength of the extrusion product was over than 350MPa. It is far stronger than that of the human cortical bone (200MPa). SEM observations showed that the fiber structure began to appear at an extrusion ratio ER=3, and at the extrusion ratio ER=6, the chain axes of PLLA became aligned to the extrusion direction. The structure of extrusion products at the high extrusion ratio showed highly oriented fiber structure composed of micro-fibril. At high extrusion ratio tranformation from α-crystal to β-crystal was also observed.     

Cycloaddition of Chlorosulfonyl Isocyanate to 2H-Azirines: Formation of [2+2+2] Cycloadducts

Chlorosulfonyl isocyanata (CSI) reacts with 2H-azirines 1 a-c at -78°C to form [2+2+2] cycloadducts 3a-c and 4a-c. The tricyclic aziridine derivatives 4a-c undergo CSI extrusion reactions and subsequent oxidation to the corresponding pyrazines 5a-c. Structural identifications of 3a-c and 4a-c are based on ir, nmr and mass spectral data.     

Processing of semicrystalline polymers by high-stress extrusion

A study has been conducted on the solid-state extrusion of three semicrystalline polymers:poly-propylene (PP), poly(vinylidene fluoride) (PVDF), and high-density polyethylene (HDPE). HDPE has been extruded in continuous lengths with area reductions up to 25× at temperatures substantially below the melting region. Such extrusion has been identified as a solid-state process, since measurements of the temperature of the polymer during extrusion indicate the absence of significant heating due to deformation. In contrast, continuous lengths of PP and PVDF could not be obtained substantially below their melting temperatures, indicating that crystallization during extrusion is an important process for these polymers. Under severe extrusion conditions (low temperatures, high area reductions. etc.), all three polymers failed within the tapered region of the extrusion die. Two modes of failure have been identified, brittle fracture and, surprisingly, necking. Grid-line distortion patterns and a highly simplified upper-bound plasticity analysis both indicate that shear deformations are a major factor during high-stress extrusion.     

Metallocene ethylene-1-octene copolymers: Effect of extrusion conditions on thermal oxidation of polymers with different comonomer content

Metallocene ethylene-1-octene copolymers having different densities and comonomer content ranging from 11 to 36 wt% (m-LLDPE), and a Ziegler copolymer (z-LLDPE) containing the same level of short-chain branching (SCB) corresponding to one of the m-LLDPE polymers, were subjected to extrusion. The effects of temperature (210-285 °C) and multi-pass extrusions (up to five passes) on the rheological and structural characteristics of these polymers were investigated using melt index and capillary rheometry, along with spectroscopic characterisation of the evolution of various products by FTIR, ¹³C-NMR and colour measurements. The aim is to develop a better understanding of the effects of processing variables on the structure and thermal degradation of these polymers. Results from rheology show that both extrusion temperature and the amount of comonomer have a significant influence on the polymer melt thermo-oxidative behaviour. At low to intermediate processing temperatures, all m-LLDPE polymers exhibited similar behaviour with crosslinking reactions dominating their thermal oxidation. By contrast, at higher processing temperatures, the behaviour of the metallocene polymers changed depending on the level of comonomer content: higher SCB gave rise to predominantly chain scission reactions whereas polymers with lower level of SCB continued to be dominated by crosslinking. This temperature dependence was attributed to changes in the different evolution of carbonyl and unsaturated compounds including vinyl, vinylidene and trans-vinylene.     

Effect of processing method on the structure and properties of HDPE/EAA/LDHs nanocomposites

High-density polyethylene/ethylene–acrylic acid copolymer/layered double hydroxides (LDHs) nanocomposites were prepared by the methods of one-step extrusion and twice extrusion in this paper. The structure and properties of the nanocomposites were also studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetry (TG), and the cone calorimeter. The results of XRD, SEM, and TEM analyses demonstrated that the method of twice extrusion gave the LDHs a higher level of exfoliation within the matrix compared with the method of one-step extrusion. The DSC and TG analysis revealed that the crystalline property and the thermal stability of the nanocomposites could be improved by the method of secondary extrusion. The cone calorimeter test showed that the method of secondary extrusion could improve the flame retardant property of the nanocomposites to some degree.     

Synthesis and Physical Properties of Sterically Congested Cycloalkenes, 1,2-Di-tert-butyl-3,3,5,5-tetramethylcyclopentene and 1,2-Di-tert-butyl-3,3,6,6-tetramethylcyclohexene

Two sterically congested cycloalkenes (9 and 10), congeners of tetra-tert-butylethylene, were synthesized and characterized. Oxidation of the bicyclic 1,3-dithietane 8 with dimethyldioxirane (DMD) gave the endo,endo-disulfoxide 13, thermal isomerization of which to the endo,exo-disulfoxide 15 followed by oxidation with DMD gave the trioxide 18. Heating 18 in refluxing 1,3-dimethyl-2-imidazolidinone furnished 1,2-di-tert-butyl-3,3,5,5-tetramethylcyclopentene (9) in 69% yield by a 2-fold extrusion process. The reaction of the 1,6-diketone dihydrazone 23 with Se(2)Cl(2) gave the selenadiazoline 34 and the 1,3-diselenetane 35. Heating 34 at 115-130 degrees C gave 1,2-di-tert-butyl-3,3,6,6-tetramethylcyclohexene (10), a "didehydro" derivative of tetra-tert-butylethylene, in 43% yield. The C=C bond in 10 is strained in degree comparable to those of most strained alkenes reported so far.     

Solid-phase extrusion of polyamide under simple shear

The advantages of new simple-shear methods of severe plastic deformation (equal-channel multiple angular extrusion, T-type extrusion, and twist extrusion) are examined for polyamides from the viewpoint of the structural modification of flexible-chain semicrystalline polymers. The effect of the deformation scheme and mode and the extrusion temperature and rate on the physicomechanical characteristics of the processed polymers are studied. The behavior of the material and its specific features are considered with respect to the conditions of solid-phase extrusion.     

Influence of extrusion ratio on the thermal properties and morphology of ultradrawn high-density polyethylene

Solid-state extrusion of high-density polyethylene (HDPE) has received considerable attention. It has been shown that extrudate may have high values of optical clarity, tensile modulus (～70 GPa = 7 × 10¹¹ dyn/cm²), and c-axis orientation. The effects of extrusion conditions on the properties of the resultant fibers have, however, not yet been clarified. A systematic study has thus been made here to evaluate extrusion pressure, temperature, and extrusion (draw) ratio, and the molecular weight of extruded HDPE. The effects of extrusion ratio on the degree of crystallinity, melting behavior, crystal orientation, and dimensional change along the extrusion direction are reported.