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Title: Crystallization and melting of a branched polyethylene with precisely controlled chemical structure

Abstract

The heat capacity of a linear polyethylene with dimethyl branches, at every 21st backbone atom was analyzed by differential scanning calorimetry (DSC) and quasi-isothermal temperature-modulated DSC. This novel copolyethylene (PE2M) is relatively difficult to crystallize from the melt. On subsequent heating, a first, sharp melting peak is followed by a sharp cold-crystallization and crystal perfection and a smaller endotherm, before reaching the main melting at 315-320 K, close to the melting temperatures of eicosane and tetracontane. The low-temperature melting is sensitive to the cooling rate and disappears below 1.0 K min-1. The cold crystallization can be avoided by heating with rates faster than 80 K min-1. The PE2M exhibits some reversing and reversible melting, which is typical for chain-folded polymers. The glass transition of semicrystalline PE2M is broadened and reaches its upper limit at about 260 K (midpoint at about 0.355 K). Above this temperature, the crystals seem to have a heat capacity similar to that of the liquid. A hypothesis is that the melting transition can be explained by changes in crystal perfection without major alteration of the crystal structure and the lamellar morphology.

Authors:
 [1];  [2];  [3];  [4];  [5];  [2]
  1. University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
  2. {nmn} [ORNL
  3. University of Tennessee, Knoxville (UTK)
  4. {Tony} [ORNL
  5. University of Florida
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931364
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Polymer Science, Part B: Polymer Physics; Journal Volume: 44; Journal Issue: 24
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMS; CALORIMETRY; CRYSTAL STRUCTURE; CRYSTALLIZATION; GLASS; HEATING; HYPOTHESIS; MELTING; MORPHOLOGY; POLYETHYLENES; POLYMERS; SPECIFIC HEAT

Citation Formats

Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, Wagener, Kenneth, and Wunderlich, Bernhard. Crystallization and melting of a branched polyethylene with precisely controlled chemical structure. United States: N. p., 2006. Web.
Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, Wagener, Kenneth, & Wunderlich, Bernhard. Crystallization and melting of a branched polyethylene with precisely controlled chemical structure. United States.
Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, Wagener, Kenneth, and Wunderlich, Bernhard. Sun . "Crystallization and melting of a branched polyethylene with precisely controlled chemical structure". United States. doi:.
@article{osti_931364,
title = {Crystallization and melting of a branched polyethylene with precisely controlled chemical structure},
author = {Qui, Wulin and Pyda, Marek and Nowak-Pyda, Elisabieta and Habenschuss, Anton and Wagener, Kenneth and Wunderlich, Bernhard},
abstractNote = {The heat capacity of a linear polyethylene with dimethyl branches, at every 21st backbone atom was analyzed by differential scanning calorimetry (DSC) and quasi-isothermal temperature-modulated DSC. This novel copolyethylene (PE2M) is relatively difficult to crystallize from the melt. On subsequent heating, a first, sharp melting peak is followed by a sharp cold-crystallization and crystal perfection and a smaller endotherm, before reaching the main melting at 315-320 K, close to the melting temperatures of eicosane and tetracontane. The low-temperature melting is sensitive to the cooling rate and disappears below 1.0 K min-1. The cold crystallization can be avoided by heating with rates faster than 80 K min-1. The PE2M exhibits some reversing and reversible melting, which is typical for chain-folded polymers. The glass transition of semicrystalline PE2M is broadened and reaches its upper limit at about 260 K (midpoint at about 0.355 K). Above this temperature, the crystals seem to have a heat capacity similar to that of the liquid. A hypothesis is that the melting transition can be explained by changes in crystal perfection without major alteration of the crystal structure and the lamellar morphology.},
doi = {},
journal = {Journal of Polymer Science, Part B: Polymer Physics},
number = 24,
volume = 44,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}