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An analysis of the β transition of linear and branched polyethylenes by carbon‐13 NMR

1982; Wiley; Volume: 20; Issue: 4 Linguagem: Inglês

10.1002/pol.1982.180200407

1542-9385

James J. Dechter, David E. Axelson, A. Dekmezian, M. Glotin, L. Mandelkern,

Advanced MRI Techniques and Applications

Abstract Carbon‐13 nuclear magnetic resonance relaxation parameters have been obtained as a function of temperature for a set of branched polyethylenes whose β transition temperatures were determined independently. Resolvable spectra could be obtained at temperatures either corresponding to or very close to the temperature of the β transition. Together with results for other systems, these observations preclude the indentification of the β transition with the glass temperature. From the measured spin relaxation times and nuclear Overhauser enhancements average correlation times were calculated as a function of temperature. The average correlation times were calculated as a function of temperature. The average correlation time is on the order of 10 −8 −10 −9 s at the β transition. These results argue strongly against it being assigned to the glass temperature.