scholarly journals Synthesis of polydicyclopentadiene using the Cp2TiCl2/Et2AlCl catalytic system and thin-layer oxidation of the polymer in air

2019 ◽  
Vol 15 ◽  
pp. 733-745
Author(s):  
Zhargolma B Bazarova ◽  
Ludmila S Soroka ◽  
Alex A Lyapkov ◽  
Мekhman S Yusubov ◽  
Francis Verpoort
Keyword(s):  
Catalytic System ◽  
Structural Changes ◽  
Atmospheric Oxygen ◽  
Thin Layers ◽  
Polymerization Process ◽  
Physical Parameters ◽  
Titanium Dichloride ◽  
Blue Discoloration ◽  
Oxygen Oxidation ◽  
Kinetic Mode

The polymerization process of dicyclopentadiene using a multicomponent catalytic system based on bis(cyclopentadienyl)titanium dichloride and diethylaluminum chloride was studied. It was demonstrated that the application of an excess of the aluminum component leads to the formation of stable charged complexes of blue discoloration, which initiate cationic polymerization of dicyclopentadiene. Unstabilized thin layers of obtained polydicyclopentadiene undergo oxidation and structuring under atmospheric oxygen. Oxidation of polydicyclopentadiene films in air occurs slowly during several weeks and can be determined by the increase of carbonyl and hydroxyl adsorption bands in infrared spectra. Along with oxidation, cross-linking processes occur in polymers, which lead to a change in physical parameters of the layers, and more precisely to a decrease in the permeability of atmospheric oxygen through the layers. Consequently, this leads to the transition of the oxidation from a kinetic mode into a diffusive mode. Such structural changes do not occur in a polymer that was stabilized by adding an antioxidant.

scholarly journals Interacting Binary White Dwarf Stars

1992 ◽  
Vol 151 ◽  
pp. 461-464
Author(s):  
J.-E. Solheim
Keyword(s):  
White Dwarf ◽  
Structural Changes ◽  
Light Curves ◽  
Physical Parameters ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Test Models ◽  
Radial Pulsations ◽  
Whole Earth

This group of stars consists of 4 systems, also called helium cataclysmics. Three of them show photometric variations and have been studied by the Whole Earth Telescope (WET), which have revealed multiperiodic light curves showing the signature of g-mode non-radial pulsations on the accreting star. The combination of accretion and g-mode pulsations gives a unique opportunity to test models for the accreator's structural changes in response to accretion. IUE-spectra provide additional physical parameters.

Chemical, Mechanical and Electrical Properties of Glassy Polymeric Carbon

2006 ◽  
Vol 929 ◽  
Author(s):  
Iulia Muntele ◽  
Claudiu I. Muntele ◽  
Renato Minamisawa ◽  
Bopha Chhay ◽  
Daryush Ila
Keyword(s):  
Atomic Oxygen ◽  
Structural Changes ◽  
Phenolic Resin ◽  
Large Strain ◽  
Atmospheric Oxygen ◽  
Low Density ◽  
Mechanical And Electrical Properties ◽  
Three Stages ◽  
Polymeric Carbon ◽  
Small Thermal Expansion

ABSTRACTGlassy Polymeric Carbon (GPC) is obtained by a molding technique, in various shapes, from a phenolic resin precursor. The heat treatment of the precursor is achieved in three stages up to 1000 °C. Similar GPC materials produced in our laboratory displayed large strain to failure ratio, small thermal expansion coefficient and low density. Like all carbon forms, is attacked by oxygen, especially atomic oxygen. Nevertheless the kinetics for reaction with atmospheric oxygen is very slow. We investigated the composition and structural changes of the phenolic precursor as a function of temperature and evaluated materials stability when exposed to high temperatures in presence of hydrogen or oxygen.

scholarly journals Characteristics of raw and cooked fillets in species of actual and potential interest for Italian aquaculture

2015 ◽  
Author(s):  
Roberta Martelli
Keyword(s):  
Rainbow Trout ◽  
Structural Changes ◽  
Fish Muscle ◽  
Physical Parameters ◽  
Chemical Profile ◽  
Farmed Fish ◽  
Extrinsic Factors ◽  
Physico Chemical ◽  
Chemical Traits ◽  
Sampling Times

Heat treatment generally induces structural changes of fish muscle and loss of nutrients. Depending on many intrinsic and extrinsic factors farmed fish qualitative attributes can be subject to changes. The aim of this study was to assess the effects of boiling on physical parameters and nutritional profile of fillets from two farmed species [meagre (Argyrosomus regius) and rainbow trout (Onchorynchus mykiss)]. Specie-specific differences in physico-chemical traits influenced raw flesh quality and the response to cooking. In meagre, sampling times differences in macronutrients were nullified by cooking. In rainbow trout, boiling modified physico-chemical profile depending on the strain while farming conditions affected cooked fillet quality in a different extent according to the strain.

Assessment of Tribological Properties of Low Friction Thin Layers Produced by Vacuum Methods

2019 ◽  
Vol 293 ◽  
pp. 125-140
Author(s):  
Agnieszka Paradecka ◽  
Krzysztof Lukaszkowicz ◽  
Jozef Sondor
Keyword(s):  
Wear Resistance ◽  
Friction Coefficient ◽  
Chemical Analysis ◽  
Coefficient Of Friction ◽  
Tribological Properties ◽  
Structural Changes ◽  
Thin Layers ◽  
Low Friction ◽  
Topographic Analysis ◽  
Steel Substrates

Low friction thin layers are an excellent alternative for conventional coatings. They provide increased life of the elements, to which they were applied, due to enhancing the hardness or chemical and electrochemical resistance. They help to avoid the cracks, oxidation, as well as possible structural changes during the element's work. However, they primarily improve tribological properties by increasing wear resistance and reducing the friction. This also applies to components operating under variable conditions such as load, speed, temperature. The presented article analyzes the properties of various low-friction thin layers deposited by vacuum methods on the steel substrates. DLC, TiC, MoS2, CrCN thin layers were chosen, as they achieve the lowest possible coefficient of friction. In the framework of this work the measurements of adhesion of the investigated layers to the substrate as well as the friction coefficient, chemical analysis, microstructure and topographic analysis of the low-friction layers were carried out.

The Effect of Film Thickness on EHD-Driven Instability of Interface Separating Two Liquids

2009 ◽  
Author(s):  
Payam Sharifi ◽  
Asghar Esmaeeli
Keyword(s):  
Stokes Equations ◽  
Thin Liquid Film ◽  
Front Tracking ◽  
Thin Layers ◽  
Navier Stokes ◽  
Physical Parameters ◽  
Interface Instability ◽  
Navier Stokes Equations ◽  
Dielectric Model ◽  
Leaky Dielectric Model

Most of the studies conducted so far on EHD-driven instability of superimposed fluids have been concerned with liquid layers of modest depths. In many applications, however, the liquid layers can be very thin. Since the dynamics in thin films is generally governed by lubrication equations rather than full Navier-Stokes equations, it is expected that the interface dynamics will be quite different from that of the liquids with modest depths. The objective of this study is to explore the effect of initial liquid thickness on the dynamics of the phase boundary. To do this end, we perform Direct Numerical Simulations (DNS) using a front tracking/finite difference scheme, in conjunction with Taylor’s leaky dielectric model. For the physical parameters used here, it is shown that for sufficiently thick liquid layers, the interface instability leads to formation of liquid columns that merge together to form a big column. However, for thin layers, the interactions between the columns are weaker and lead to a short and a longer column that are connected by a thin liquid film.

Ethene/Norbornene Copolymerization with (Isodicyclopentadienyl)titanium Complex-MAO Catalyst

2007 ◽  
Vol 72 (5-6) ◽  
pp. 697-702 ◽  
Author(s):  
Sébastien Gentil ◽  
Nadine Pirio ◽  
Philippe Meunier ◽  
Fabrice Gallou ◽  
Leo A. Paquette
Keyword(s):  
Catalytic System ◽  
Catalyst System ◽  
Titanium Complex ◽  
Titanium Dichloride

Norbornene (NB) homopolymerization and ethene/NB copolymerizations with a silylene-bridged (isodicyclopentadienyl)(tert-butylamido)titanium dichloride-methylalumoxane (MAO) catalyst system were investigated. This catalytic system shows no efficiency towards NB homopolymerization but produces poly(ethene-co-norbornene)s. An increase in the initial NB feed content leads to a loss of copolymerization activity as well as NB copolymer incorporation. The structure of the isodicyclopentadienyl fragment (IsodiCp) has a strong limiting effect on comonomer incorporation possibilities.

scholarly journals LIQUID PHASE CATALYTIC OXIDATION 3,5 – XYLENOL

2020 ◽  
Vol 63 (3) ◽  
pp. 4-9
Author(s):  
Nina V. Lebedeva ◽  
George N. Koshel ◽  
Sergei G. Koshel
Keyword(s):  
Activation Energy ◽  
Catalytic System ◽  
Atmospheric Oxygen ◽  
Practical Interest ◽  
High Rate ◽  
Hydroxyl Group ◽  
Effect Of Temperature ◽  
Acetic Acid Medium ◽  
Starting Compound ◽  
Oxidative Transformations

5-Hydroxyisophthalic acid is of practical interest in the synthesis of polymers, drugs, cosmetics. The methods for its preparation described in the literature are characterized by a number of significant drawbacks, which hinders the use of this compound in the development of new materials with valuable consumer properties. In this regard, a method for the synthesis of 5-hydroxyisophthalic acid by the oxidation of 3, 5-xylenol has been developed. It has been established that the hydroxyl group inhibits the oxidation of methyl groups; therefore, to carry out oxidative transformations, the hydroxyl group was replaced by acetyl. For this, 3,5-xylenol was acylated with acetic anhydride in the presence of sulfuric acid. The resulting 3, 5-dimethylphenylacetate is oxidized by atmospheric oxygen in an acetic acid medium in the presence of a catalytic system containing cobalt acetals manganese and bromide ions up to 5-acetoxyisophthalic acid. The effect of temperature on the reaction was studied and the activation energy was determined. It was 50 ± 5 kJ/mol that corresponds to the activation energy of oxidation of alkylaromatic hydrocarbons. The dependence of the rate of the process and the yield of the target product on the concentrations of the starting compound and the components of the catalytic system is investigated. It has been established that carrying out the oxidation process of 3,5-dimethylphenylacetate at its initial concentration of 0.75 mol/l, temperature 110 °C and cobalt (II) acetate concentration 0.1 mol/l, sodium bromide 0.05 mol/l, manganese (II) acetate 0.003 mol/l provides the reaction with high rate and the yield of 5-acetoxyisophthalic acid 70-75%. In these conditions, the balance experiment was carried out. 5-Acetoxyisophthalic acid is of practical interest as a monomer for heat-resistant polymers. To obtain 5-hydroxyisophthalic acid, 5-acetoxyisophthalic acid is subjected to alkaline hydrolysis.

1,4,7-Tricarboxymethyl-1,4,7-triazacyclononane Copper Catalyzed Oxidative Polymerization to Form Poly(2,6-dimethyl-1,4-phenylene oxide) in Water

2010 ◽  
Vol 63 (3) ◽  
pp. 502 ◽  
Author(s):  
Sweta Pant ◽  
Milton T. W. Hearn ◽  
Kei Saito
Keyword(s):  
Catalytic System ◽  
Oxidative Polymerization ◽  
Water Soluble ◽  
Polymerization Process ◽  
Alkaline Water ◽  
Phenylene Oxide ◽  
Soluble Ligand

The copper(II) complex of the water soluble ligand 1,4,7-tricarboxymethyl-1,4,7-triazacyclononane has been employed as a catalyst for the oxidative polymerization of 2,6-dimethylphenol using alkaline water as the solvent. With this catalytic system, the polymer, poly(2,6-dimethyl-1,4-phenylene oxide), was successfully obtained with suppression of the formation of the quinone by-product, 4-(3,5-dimethyl-4-oxo-2,5-cyclo-hexadienylidene)-2,6-dimethyl-2,5-cyclohexadienone, during the polymerization process.

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