The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Chitra Agashe - One of the best experts on this subject based on the ideXlab platform.
-
Morphological Investigations of Electrochemically Deposited Polyaniline Films
Polymer Journal, 1995Co-Authors: A. G. Bedekar, S. F. Patil, R C Patil, Chitra AgasheAbstract:The effect of rate of mass transfer on the surface morphology of electrochemically deposited polyaniline films was studied using scanning electron microscopy (SEM). The rate of mass transfer was controlled by varying the sheet resistance of electrode and the Monomer Concentration. Both these parameters are found to affect the deposition process and the surface morphology to a considerable extent. The polyaniline film deposited using 0.1 M Monomer Concentration on electrode with 50 Ω/□ sheet resistance shows a granular structure joined together with fine fibrils. Increase in the Monomer Concentration and decrease in the sheet resistance of the electrode lead to the enhancement in the growth of the polymer film as revealed from the current time transient measurements. The formation of fibres with different shapes such as rope-like, curved, cyclone-like, petal-like, wavy, wing-like, and criss-cross linking depends on the growth conditions of films. The sheet resistance of electrode mainly determines the number density of these fibres, whereas, the patterning is governed by the Monomer Concentration.
-
Influence of Monomer Concentration, surface resistance of electrode and current strength on electrochemically deposited poly(o-anisidine) films
Materials Chemistry and Physics, 1995Co-Authors: A. G. Bedekar, S. F. Patil, Rahul Chandrakant Patil, Chitra AgasheAbstract:Abstract The effect of Monomer Concentration, surface resistance of electrode (SnO 2 :F coated transparent glass) and current strength on the optical and thermal properties of galvanostatically deposited poly( o -anisidine) films was investigated. Of the three parameters, the Monomer Concentration was found to affect the film properties markedly. The optical spectra showed that a higher selectivity in obtaining the conducting emeraldine phase can be achieved by the proper combination of surface resistance of electrode and current strength, especially at low Concentration. Thermogravimetric analysis revealed a positive shift in the final decomposition temperature with increasing Monomer Concentration, thereby suggesting that a lower Monomer Concentration is suitable for the formation of the emeraldine salt form of the polymer. The scanning electron micrographs show that the films exhibit a fibrillar morphology; the density as well as the length of the fibres seem to increase with the Monomer Concentration.
-
Influence of Monomer Concentration and electrode conductivity on morphology of poly(o-anisidine) films
Journal of Physics D: Applied Physics, 1994Co-Authors: A. G. Bedekar, S. F. Patil, Rahul Chandrakant Patil, Chitra AgasheAbstract:The influence of Monomer Concentration and electrode conductivity on the morphology of electrochemically deposited poly (o-anisidine) films has been investigated using scanning electron microscopy. The films are found to exhibit a fibrillar morphology, except on lower conductivity electrodes and at lower Concentrations of the Monomer. The Monomer Concentration predominantly governs the rate of reaction and deposition of films; the effect of which is observed in terms of various types of patterning of fibres, namely anastomistic, reticulate, stillate, flabellate and so on. The number density of fibres is seen to be affected by the electrode conductivity.
Robert Zeigler - One of the best experts on this subject based on the ideXlab platform.
-
effect of Monomer Concentration on propene polymerization with the rac ethylenebis 1 indenyl zirconium dichloride methylaluminoxane catalyst
Macromolecules, 1995Co-Authors: Luigi Resconi, Anna Fait, Fabrizio Piemontesi, Marcello Colonnesi, Helena Rychlicki, Robert ZeiglerAbstract:The structural details of isotactic polypropene (iPP) produced with the moderately isospecific racemic-ethylenebis(1-indenyl)zirconium dichloride/methylaluminoxane (rac-(EBI)ZrCl 2 /MAO) catalyst are strongly dependent on Monomer Concentration. Polymerizing propene at 50 °C in toluene, at propene Concentrations in the experimentally measurable range 0.4-11 mol/L, rac-(EBI)ZrCl 2 /MAO shows activities in the range 2-350 kg PP /(mmol Zr .h) and yields polypropenes with M v 's from 8800 to 36 600, percent mmmm pentads ranging from 54 to 86%, and corresponding melting temperatures from 86 to 136 °C. Two types of regioirregular (secondary) placements in an isotactic sequence of primary propene insertions are observed in iPP synthesized in liquid Monomer, erythro (E, ca. 0.4%) and threo (T, ca. 0.2%). These secondary units are gradually converted into 1,3 propene units as the Monomer Concentration is lowered. In starved catalyst conditions, that is, as [M] → 0, rac-(EBI)ZrCl 2 /MAO produces atactic propene oligomers (M n = 1080, mmmm = 9.1%). These effects are the most probable cause for the discordance of literature data on metallocene-catalyzed propene polymerization. Three chain transfer mechanisms have been detected : β-hydrogen transfer to the metal and β-hydrogen transfer to the Monomer, both occurring after a primary insertion, and β-hydrogen transfer to the Monomer after a secondary insertion with the exclusive formation of a cis-2-butenyl end group.
-
Effect of Monomer Concentration on Propene Polymerization with the rac-[Ethylenebis(1-indenyl)]zirconium Dichloride/Methylaluminoxane Catalyst
Macromolecules, 1995Co-Authors: Luigi Resconi, Anna Fait, Fabrizio Piemontesi, Marcello Colonnesi, Helena Rychlicki, Robert ZeiglerAbstract:The structural details of isotactic polypropene (iPP) produced with the moderately isospecific racemic-ethylenebis(1-indenyl)zirconium dichloride/methylaluminoxane (rac-(EBI)ZrCl 2 /MAO) catalyst are strongly dependent on Monomer Concentration. Polymerizing propene at 50 °C in toluene, at propene Concentrations in the experimentally measurable range 0.4-11 mol/L, rac-(EBI)ZrCl 2 /MAO shows activities in the range 2-350 kg PP /(mmol Zr .h) and yields polypropenes with M v 's from 8800 to 36 600, percent mmmm pentads ranging from 54 to 86%, and corresponding melting temperatures from 86 to 136 °C. Two types of regioirregular (secondary) placements in an isotactic sequence of primary propene insertions are observed in iPP synthesized in liquid Monomer, erythro (E, ca. 0.4%) and threo (T, ca. 0.2%). These secondary units are gradually converted into 1,3 propene units as the Monomer Concentration is lowered. In starved catalyst conditions, that is, as [M] → 0, rac-(EBI)ZrCl 2 /MAO produces atactic propene oligomers (M n = 1080, mmmm = 9.1%). These effects are the most probable cause for the discordance of literature data on metallocene-catalyzed propene polymerization. Three chain transfer mechanisms have been detected : β-hydrogen transfer to the metal and β-hydrogen transfer to the Monomer, both occurring after a primary insertion, and β-hydrogen transfer to the Monomer after a secondary insertion with the exclusive formation of a cis-2-butenyl end group.
Willibrordus Petrus Maria Van Swaaij - One of the best experts on this subject based on the ideXlab platform.
-
polymerization of liquid propylene with a fourth generation ziegler natta catalyst influence of temperature hydrogen Monomer Concentration and prepolymerization method on powder morphology
Journal of Applied Polymer Science, 2003Co-Authors: J T M Pater, Gunter Weickert, Willibrordus Petrus Maria Van SwaaijAbstract:Liquid propylene was polymerized in a 5-L autoclave batch reactor using a commercially available TiCl4/MgCl2/Al(ethyl)3/DCPDMS Ziegler-Natta catalyst, with a phthalate ester as internal electron donor. The powders from these polymerizations were characterized using laser diffraction particle size distribution (PSD) analysis, scanning electron microscopy (SEM), and bulk density measurements. These characteristics were analyzed as a function of the process conditions, including hydrogen and Monomer Concentration, polymerization temperature, and the prepolymerization method. It was shown that polymerization temperature influences the powder morphology to a large extent. At low temperatures, high-density particles were obtained, showing regular shaped particle surfaces and low porosities. With increasing temperature, the morphology gradually was transferred into a more open structure, with irregular surfaces and poor replication of the shape of the catalyst particle. When using a prepolymerization step at a relatively low temperature, the morphology obtained was determined by this prepolymerization step and was independent from conditions in main polymerization. The morphology obtained was the same as that observed after a full polymerization at temperature. Even when using a short polymerization at an increasing temperature, the morphology was strongly influenced by the initial conditions. The effect of variation in hydrogen Concentration supported the conclusion that the initial polymerization rate determines the powder morphology. In the absence of hydrogen, high bulk densities, and regularly shaped particles were obtained, even at high temperatures. With increasing hydrogen Concentration, the reaction rates increased rapidly, and with that changed the morphology.
-
polymerization of liquid propylene with a 4th generation ziegler natta catalyst influence of temperature hydrogen and Monomer Concentration and prepolymerization method on polymerization kinetics
Chemical Engineering Science, 2002Co-Authors: J T M Pater, Gunter Weickert, Willibrordus Petrus Maria Van SwaaijAbstract:In a batch-wise operated autoclave reactor, liquid propylene was polymerized using a 4th generation, TiCl4/MgCl2/phthalate ester-AlEt3-R2Si(OMe)2, Ziegler-Natta catalyst system. By using a calorimetric principle it was possible to measure full reaction rate versus time curves for obtaining data on polymerization kinetics, under industrially relevant conditions. The influence of polymerization temperature, the hydrogen and Monomer Concentration, and the prepolymerization method on reaction kinetics were investigated. A new method for prepolymerization, the so-called non-isothermal prepolymerization, is described. In this short prepolymerization procedure featuring an increasing polymerization temperature the thermal runaway on particle scale was avoided. It was shown that this prepolymerization method can relatively easily be applied to an industrial process, with the introduction of a continuous plug flow reactor, giving a narrow residence time distribution, acceptable yield-in-prepolymerization and a method for monitoring catalyst activity. Using different methods for calculating the Monomer Concentration at the active site of the catalyst, the influence of polymerization temperature was determined. It was shown that at high polymerization temperatures, the reaction rate is barely influenced by polymerization temperature, when no prepolymerization is used. This is ascribed to thermal runaway on particle scale of a fraction of the catalyst particles. When a prepolymerization is used, this effect disappears and thermal runaway is avoided. When systematically reducing the Monomer Concentration (Cm,bulk) in the bulk by replacing part of the liquid propylene by hexane, the reaction rate proved to be remarkably independent of the Monomer Concentration. With reducing Cm,bulk, reaction rate decreased very slowly until Cm,bulk=150 g/l. When further decreasing Cm,bulk, reaction rate dropped rapidly. The hydrogen Concentration was varied over a wide range at 60°C and 70°C. For both temperatures it was shown that reaction rates increased rapidly with increasing hydrogen Concentration at low hydrogen Concentrations. At higher hydrogen amounts, this effect disappeared and a maximum reaction rate was found.
A. G. Bedekar - One of the best experts on this subject based on the ideXlab platform.
-
Effect of Monomer Concentration and substrate resistance on redox behaviour of polyaniline films
Materials Chemistry and Physics, 1997Co-Authors: A. G. Bedekar, S. F. Patil, Rahul Chandrakant Patil, K. VijayamohananAbstract:Abstract The effect of Monomer Concentration and substrate resistance on the redox properties of polyaniline is investigated using cyclic voltammetry, The mechanism of polymerization is found to be affected drastically by the Concentration of Monomer while the influence of substrate resistance seems to become a predominant factor only at higher Concentration. Both these parameters in combination are found to be responsible for the flattening of cyclic voltammograms due to a significant contribution of the uncompensated ohmic resistance. The extent of reversibility is observed to be a strong function of scan rate and the optimum oxidation-reduction transformation occur at a scan rate of 100 mV s − at moderate Monomer Concentrations. Additionally, from the optical spectra it is observed that 0.2 M Monomer Concentration is seen to be appropriate for obtaining selectively the conducting phase of the polymer.
-
Morphological Investigations of Electrochemically Deposited Polyaniline Films
Polymer Journal, 1995Co-Authors: A. G. Bedekar, S. F. Patil, R C Patil, Chitra AgasheAbstract:The effect of rate of mass transfer on the surface morphology of electrochemically deposited polyaniline films was studied using scanning electron microscopy (SEM). The rate of mass transfer was controlled by varying the sheet resistance of electrode and the Monomer Concentration. Both these parameters are found to affect the deposition process and the surface morphology to a considerable extent. The polyaniline film deposited using 0.1 M Monomer Concentration on electrode with 50 Ω/□ sheet resistance shows a granular structure joined together with fine fibrils. Increase in the Monomer Concentration and decrease in the sheet resistance of the electrode lead to the enhancement in the growth of the polymer film as revealed from the current time transient measurements. The formation of fibres with different shapes such as rope-like, curved, cyclone-like, petal-like, wavy, wing-like, and criss-cross linking depends on the growth conditions of films. The sheet resistance of electrode mainly determines the number density of these fibres, whereas, the patterning is governed by the Monomer Concentration.
-
Influence of Monomer Concentration, surface resistance of electrode and current strength on electrochemically deposited poly(o-anisidine) films
Materials Chemistry and Physics, 1995Co-Authors: A. G. Bedekar, S. F. Patil, Rahul Chandrakant Patil, Chitra AgasheAbstract:Abstract The effect of Monomer Concentration, surface resistance of electrode (SnO 2 :F coated transparent glass) and current strength on the optical and thermal properties of galvanostatically deposited poly( o -anisidine) films was investigated. Of the three parameters, the Monomer Concentration was found to affect the film properties markedly. The optical spectra showed that a higher selectivity in obtaining the conducting emeraldine phase can be achieved by the proper combination of surface resistance of electrode and current strength, especially at low Concentration. Thermogravimetric analysis revealed a positive shift in the final decomposition temperature with increasing Monomer Concentration, thereby suggesting that a lower Monomer Concentration is suitable for the formation of the emeraldine salt form of the polymer. The scanning electron micrographs show that the films exhibit a fibrillar morphology; the density as well as the length of the fibres seem to increase with the Monomer Concentration.
-
Influence of Monomer Concentration and electrode conductivity on morphology of poly(o-anisidine) films
Journal of Physics D: Applied Physics, 1994Co-Authors: A. G. Bedekar, S. F. Patil, Rahul Chandrakant Patil, Chitra AgasheAbstract:The influence of Monomer Concentration and electrode conductivity on the morphology of electrochemically deposited poly (o-anisidine) films has been investigated using scanning electron microscopy. The films are found to exhibit a fibrillar morphology, except on lower conductivity electrodes and at lower Concentrations of the Monomer. The Monomer Concentration predominantly governs the rate of reaction and deposition of films; the effect of which is observed in terms of various types of patterning of fibres, namely anastomistic, reticulate, stillate, flabellate and so on. The number density of fibres is seen to be affected by the electrode conductivity.
Luigi Resconi - One of the best experts on this subject based on the ideXlab platform.
-
effect of Monomer Concentration on propene polymerization with the rac ethylenebis 1 indenyl zirconium dichloride methylaluminoxane catalyst
Macromolecules, 1995Co-Authors: Luigi Resconi, Anna Fait, Fabrizio Piemontesi, Marcello Colonnesi, Helena Rychlicki, Robert ZeiglerAbstract:The structural details of isotactic polypropene (iPP) produced with the moderately isospecific racemic-ethylenebis(1-indenyl)zirconium dichloride/methylaluminoxane (rac-(EBI)ZrCl 2 /MAO) catalyst are strongly dependent on Monomer Concentration. Polymerizing propene at 50 °C in toluene, at propene Concentrations in the experimentally measurable range 0.4-11 mol/L, rac-(EBI)ZrCl 2 /MAO shows activities in the range 2-350 kg PP /(mmol Zr .h) and yields polypropenes with M v 's from 8800 to 36 600, percent mmmm pentads ranging from 54 to 86%, and corresponding melting temperatures from 86 to 136 °C. Two types of regioirregular (secondary) placements in an isotactic sequence of primary propene insertions are observed in iPP synthesized in liquid Monomer, erythro (E, ca. 0.4%) and threo (T, ca. 0.2%). These secondary units are gradually converted into 1,3 propene units as the Monomer Concentration is lowered. In starved catalyst conditions, that is, as [M] → 0, rac-(EBI)ZrCl 2 /MAO produces atactic propene oligomers (M n = 1080, mmmm = 9.1%). These effects are the most probable cause for the discordance of literature data on metallocene-catalyzed propene polymerization. Three chain transfer mechanisms have been detected : β-hydrogen transfer to the metal and β-hydrogen transfer to the Monomer, both occurring after a primary insertion, and β-hydrogen transfer to the Monomer after a secondary insertion with the exclusive formation of a cis-2-butenyl end group.
-
Effect of Monomer Concentration on Propene Polymerization with the rac-[Ethylenebis(1-indenyl)]zirconium Dichloride/Methylaluminoxane Catalyst
Macromolecules, 1995Co-Authors: Luigi Resconi, Anna Fait, Fabrizio Piemontesi, Marcello Colonnesi, Helena Rychlicki, Robert ZeiglerAbstract:The structural details of isotactic polypropene (iPP) produced with the moderately isospecific racemic-ethylenebis(1-indenyl)zirconium dichloride/methylaluminoxane (rac-(EBI)ZrCl 2 /MAO) catalyst are strongly dependent on Monomer Concentration. Polymerizing propene at 50 °C in toluene, at propene Concentrations in the experimentally measurable range 0.4-11 mol/L, rac-(EBI)ZrCl 2 /MAO shows activities in the range 2-350 kg PP /(mmol Zr .h) and yields polypropenes with M v 's from 8800 to 36 600, percent mmmm pentads ranging from 54 to 86%, and corresponding melting temperatures from 86 to 136 °C. Two types of regioirregular (secondary) placements in an isotactic sequence of primary propene insertions are observed in iPP synthesized in liquid Monomer, erythro (E, ca. 0.4%) and threo (T, ca. 0.2%). These secondary units are gradually converted into 1,3 propene units as the Monomer Concentration is lowered. In starved catalyst conditions, that is, as [M] → 0, rac-(EBI)ZrCl 2 /MAO produces atactic propene oligomers (M n = 1080, mmmm = 9.1%). These effects are the most probable cause for the discordance of literature data on metallocene-catalyzed propene polymerization. Three chain transfer mechanisms have been detected : β-hydrogen transfer to the metal and β-hydrogen transfer to the Monomer, both occurring after a primary insertion, and β-hydrogen transfer to the Monomer after a secondary insertion with the exclusive formation of a cis-2-butenyl end group.