Reversed Annealing of Thermal Fractionated Polyethylenes by TMDSC |
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Authors: | F Cser J L Hopewell K Tajne R A Shanks |
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Institution: | (1) Department Chemical and Metallurgical Engineering, RMIT University, P.O. Box 2476V, Melbourne, 3001, Australia;(2) CRC for Polymers, 32 Business Park Drive, Notting Hill, 3168, Australia;(3) Dept. Applied Chemistry, RMIT University, Melbourne, 3000, Australia |
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Abstract: | Polyethylene samples prepared by thermal fractionation (TF) were annealed in several consecutive cycles in a temperature modulated
DSC (TMDSC) at a temperatures one °C below the peak temperatures, increased from cycle to cycle relative to these peaks. The
transition enthalpy of each cooling cycle was greater or equal to that of the preceding heating cycle. The total heat-flows
of each heating cycle corresponded to those of the samples in the reference state up until the vicinity of the annealing temperature.
During the annealing, the heat capacities decreased to a lower value over a one minute period. The thermal memory effect caused
by the thermal fractionation was eliminated by a small overheating of the material for a short time. The fast disappearance
of the thermal memory by a relatively very small degree of heating above their melting temperature denies a long range physical
separation of macromolecules by TF.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | annealing crystallization heat capacity polyethylene TMDSC total heat-flow |
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