The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Michel H. J. Koch - One of the best experts on this subject based on the ideXlab platform.
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Lamellar and Crystalline Layer Thickness of Single Crystals of Narrow Molecular Weight Fractions of Linear Polyethylene
Macromolecules, 2002Co-Authors: Stephane Hocquet, Marcel Dosière, Y. Tanzawa, Michel H. J. KochAbstract:The thermal dependence of the lamellar thickness (Lp) and the thickness of crystalline layers (Lcryst) of Linear Polyethylene single crystals has been revisited. LPE fractions with different average molecular weights were crystallized at the same temperatures to avoid the delicate problem of an arbitrary choice of their equilibrium dissolution temperature to calculate their degree of supercooling. This procedure allows direct check of the thicknesses of the crystalline layers dependence on the degree of supercooling. Indeed, the equilibrium melting and dissolution temperatures depend on the average molecular weight. Mats of Linear Polyethylene single crystals of various narrow molecular weight fractions were obtained from dilute p-xylene solutions. Their lamellar thickness was determined from the SAXS intensity curve. The crystalline layers thickness was calculated from the Linear correlation function of the SAXS intensity curves and from the LAM mode frequency of the Raman spectrum. It depends as expecte...
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Temperature Reversible Transitions in Linear Polyethylene Studied by TMDSC and Time-Resolved, Temperature-Modulated WAXD/SAXS
Macromolecules, 2001Co-Authors: Bart Goderis, Harry Reynaers, Rolf Scherrenberg, Vincent Mathot, Michel H. J. KochAbstract:The morphological changes during the quasi-isothermal melt crystallization of a Linear Polyethylene sample at 126 °C were monitored by synchrotron WAXD and SAXS and compared to TMDSC data. A blockl...
Takashi Ishiburo - One of the best experts on this subject based on the ideXlab platform.
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Ultimate tensile behavior of Linear Polyethylene solids
Journal of Polymer Science Part B: Polymer Physics, 2002Co-Authors: Koh-hei Nitta, Takashi IshiburoAbstract:The influence of the elongation rate and temperature on the ultimate tensile properties of melt-crystallized Linear Polyethylene solids was investigated, with a double-edge-notched specimen to avoid necking, in which uniform deformation could be assumed throughout the experiment. The data on ultimate properties such as the tensile strength and elongation at break for different temperatures could be superimposed, by shifts along the elongation rate axis, to give a master curve as a function of the time to rupture. The shift factors obtained from the superpositioning of both the tensile strength and ultimate strain took the form of the Williams-Landel-Ferry equation. As a result, the ultimate data provided a failure envelope curve that made it possible to predict rupture times when the tensile tests were conducted under any experimental conditions.
Richard H. Boyd - One of the best experts on this subject based on the ideXlab platform.
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A dielectric study of molecular relaxation in Linear Polyethylene
Polymer, 1994Co-Authors: Michael S Graff, Richard H. BoydAbstract:Abstract Although the dielectric β glass-rubber relaxation has previously been observed in dipole-decorated branched Polyethylenes and in Linear Polyethylene containing several mole per cent chlorine, it has not been observed in Linear Polyethylene containing very low dipole concentrations. Dielectric relaxation has been studied here in a Linear Polyethylene specimen (containing a few carbonyl groups per 1000 methylene units) in the hope of observing the β process. The isochronal loss peak for the β relaxation is not well resolved from that for the α relaxation. However, it is found that the β process is very apparent as an increment in the isochronal dielectric constant scans. This was taken advantage of in characterizing the relaxation. In comparing the results with previous work it is found that there is a progression in the β relaxation T max location towards higher temperature as the degree of crystallinity increases through branched and Linear Polyethylene specimens.
Koh-hei Nitta - One of the best experts on this subject based on the ideXlab platform.
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Ultimate tensile behavior of Linear Polyethylene solids
Journal of Polymer Science Part B: Polymer Physics, 2002Co-Authors: Koh-hei Nitta, Takashi IshiburoAbstract:The influence of the elongation rate and temperature on the ultimate tensile properties of melt-crystallized Linear Polyethylene solids was investigated, with a double-edge-notched specimen to avoid necking, in which uniform deformation could be assumed throughout the experiment. The data on ultimate properties such as the tensile strength and elongation at break for different temperatures could be superimposed, by shifts along the elongation rate axis, to give a master curve as a function of the time to rupture. The shift factors obtained from the superpositioning of both the tensile strength and ultimate strain took the form of the Williams-Landel-Ferry equation. As a result, the ultimate data provided a failure envelope curve that made it possible to predict rupture times when the tensile tests were conducted under any experimental conditions.
Peter J. Barham - One of the best experts on this subject based on the ideXlab platform.
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Liquid-liquid phase separation in ternary blends of Linear Polyethylene with two ethylene-butene copolymers
Polymer, 1997Co-Authors: R.l. Morgan, Mary J. Hill, Peter J. Barham, C.j. FryeAbstract:Abstract A commercial ethylene-butene Linear low density Polyethylene has been fractionated by preparative temperature rising elution fractionation. Each fraction was characterized by Fourier transform infra-red spectrometry to determine the branch content and by gel permeation chromatography to determine the molecular weight. Two fractions were then blended, in various proportions, with each other and with a Linear Polyethylene. Using differential scanning calorimetry and transmission electron microscopy to examine quenched blends, the phase behaviour of this ternary system was investigated at temperatures above the melting point. The phase behaviour is very similar to that previously found for a ternary system of a Linear Polyethylene with two ethylene-octene copolymers with branch contents close to those of the ethylene-butene copolymers used in the present work. We deduce that the phase behaviour of blends containing ethylene-butene copolymers is essentially the same as that of blends containing ethylene octene copolymers. We further deduce that the length of the branches must be of secondary importance in determining phase behaviour. (Previously we have shown that the variation of molecular weight has a secondary effect on phase behaviour). Thus we conclude that in blends of Linear Polyethylene with lightly branched ethylene copolymers it is the number of branches that is the most important factor influencing the extent of phase separation in the melt.
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Absence of phase separation effects in blends of Linear Polyethylene fractions of differing molecular weight
Polymer, 1995Co-Authors: Mary J. Hill, Peter J. BarhamAbstract:Abstract Blends of Linear Polyethylenes of differing molecular weights (MWs) have been studied to try to determine whether there is any observable phase separation in the melt. Using four Linear Polyethylene fractions, of MWs between 2 × 106 and 2.5 × 103, blends were prepared and four blend systems investigated, the two high MW polymers being blended with each of the two lower MW materials in turn. The blends were studied by transmission electron microscopy and differential scanning calorimetry, techniques previously used to study blends of Linear with branched Polyethylenes. In these systems, for some compositions of blends of Linear with branched Polyethylene, quenched from some temperatures, phase separation on a scale of micrometres has been recorded. In contrast, no indications of phase separation were observed on examination of the blends of Linear with Linear Polyethylenes. From this it follows that if there is any liquid-liquid phase separation in Linear with Linear Polyethylene blends, taking place as a result of molecular weight differences, it cannot be detected by the methods used to detect liquid—liquid phase separation in Linear with branched Polyethylene blends; and, conversely, the phase separation observed in Linear with branched Polyethylene blend systems does not take place as a result of molecular weight difference alone.