The Experts below are selected from a list of 7149 Experts worldwide ranked by ideXlab platform
Saad A. Khan - One of the best experts on this subject based on the ideXlab platform.
-
effect of colloidal fillers on the cross linking of a uv curable polymer Gel Point rheology and the winter chambon criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
-
Effect of Colloidal Fillers on the Cross-Linking of a UV-Curable Polymer: Gel Point Rheology and the Winter−Chambon Criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
Bor-sen Chiou - One of the best experts on this subject based on the ideXlab platform.
-
effect of colloidal fillers on the cross linking of a uv curable polymer Gel Point rheology and the winter chambon criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
-
Effect of Colloidal Fillers on the Cross-Linking of a UV-Curable Polymer: Gel Point Rheology and the Winter−Chambon Criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
Srinivasa R. Raghavan - One of the best experts on this subject based on the ideXlab platform.
-
effect of colloidal fillers on the cross linking of a uv curable polymer Gel Point rheology and the winter chambon criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
-
Effect of Colloidal Fillers on the Cross-Linking of a UV-Curable Polymer: Gel Point Rheology and the Winter−Chambon Criterion
Macromolecules, 2001Co-Authors: Bor-sen Chiou, Srinivasa R. Raghavan, Saad A. KhanAbstract:The effect of colloidal silica fillers on the cross-linking behavior of a model UV-curable polymer system (thiol-ene) is studied using in situ rheology and real-time FTIR spectroscopy. The validity of the Winter-Chambon criterion (convergence of the loss tangents at the Gel Point) is examined for the cross-linking of these filled polymers, some of which are strongly flocculated dispersions (physical Gels) prior to chemical cross-linking. Two different types of colloidal silica particles are studied: one with octyl chains tethered to the surface and the other with methyl surface groups. The Winter-Chambon criterion is satisfied for all samples containing the methyl-terminated silica. However, the criterion breaks down for samples containing the octyl-modified silica, with the loss tangents not converging at any single Point. This suggests the absence of a self-similar critical Gel at the Gel Point in the latter case. Neither type of silica particles alters the mechanism of the cross-linking reaction, as revealed by FTIR spectroscopy, but they do retard the cross-linking kinetics. An alternate method is suggested for determining the chemical Gel Point of filled systems that fail to obey the Winter-Chambon criterion. This method involves monitoring the critical strain (limit of the linear viscoelastic region) at various UV exposure times. A dramatic increase is observed in the critical strain at the Gel Point, indicating a transition from weak, physical bonds to strong, covalent cross-links.
D. Durand - One of the best experts on this subject based on the ideXlab platform.
-
Rheological behavior of an epoxy/amine system near the Gel Point
Macromolecules, 1992Co-Authors: Didier Lairez, Mireille Adam, J. R. Emery, D. DurandAbstract:Experimental results are presented concerning the dynamic behavior of a crosslinking polymer near the Gel Point, focusing on the exponents which govern the frequency dependence of the real and imaginary parts of the shear modulus. It is found that there is only one moment during the networdk formation at which these two exponents are identical, while this behavior is predivted during a time period including the Gel Point. Nevertheless, the exponent value found is not far from the percolation and rouse model theories
-
rheological behavior of an epoxy amine system near the Gel Point
Macromolecules, 1992Co-Authors: Didier Lairez, Mireille Adam, J. R. Emery, D. DurandAbstract:Experimental results are presented concerning the dynamic behavior of a crosslinking polymer near the Gel Point, focusing on the exponents which govern the frequency dependence of the real and imaginary parts of the shear modulus. It is found that there is only one moment during the networdk formation at which these two exponents are identical, while this behavior is predivted during a time period including the Gel Point. Nevertheless, the exponent value found is not far from the percolation and rouse model theories
Rémi Deterre - One of the best experts on this subject based on the ideXlab platform.
-
The kinetic behavior of Liquid Silicone Rubber: A comparison between thermal and rheological approaches based on Gel Point determination
Reactive and Functional Polymers, 2016Co-Authors: Ali Harkous, Gael Colomines, Éric Leroy, Pierre Mousseau, Rémi DeterreAbstract:Liquid Silicone Rubber (LSR) belongs to the category of High Temperature Vulcanization rubbers (HTVs). Due to its implementation facility, its mechanical and thermal properties and its convenience for the medical and food industries, LSR is used in a wide range of applications. In order to examine LSR kinetic performances, thermal and rheometric experimental investigations are conducted to characterize the material and discuss the kinetic model describing crosslinking behavior. The Gel Point is investigated at different temperatures to improve our understanding of the different crosslinking steps and determine which characterization method (thermal or rheological) best represents the reaction. The results show that the LSR network undergoes specific development during crosslinking. Gel Point occurs before the mechanical reaction starts. Gelation behavior resembles that of a thermosetting material despite the elasto-mer properties confirmed by the thermal study. Finally, the thermal method seems more reliable to describe the crosslinking kinetics of LSR.
