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Degradation of polyethylene during extrusion. II. Degradation of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene in film extrusion

Andersson, T; Stalbom, B and Wesslén, Bengt LU (2004) In Journal of Applied Polymer Science 91(3). p.1525-1537
Abstract
The degradation of different polyethylenes-low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE)-with and without antioxidants and at different oxygen concentrations in the polymer granulates, have been studied in extrusion coating processing. The degradation was followed by online rheometry, size exclusion chromatography, surface oxidation index measurements, and gas chromatography-mass spectrometry. The degradations start in the extruder where primary radicals are formed, which are subject to the auto-oxidation when oxygen is present. In the extruder, crosslinking or chain scissions reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain... (More)
The degradation of different polyethylenes-low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE)-with and without antioxidants and at different oxygen concentrations in the polymer granulates, have been studied in extrusion coating processing. The degradation was followed by online rheometry, size exclusion chromatography, surface oxidation index measurements, and gas chromatography-mass spectrometry. The degradations start in the extruder where primary radicals are formed, which are subject to the auto-oxidation when oxygen is present. In the extruder, crosslinking or chain scissions reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain scission is overall dominating for the more linear LLDPE and HDPE resins. Additives such as antioxidants react with primary radicals formed in the melt. Degradation taking place in the film between the die orifice, and the quenching point is mainly related to the exposure time to air oxygen. Melt temperatures above 280degreesC give a dominating surface oxidation, which increases with the exposure time to air between die orifice and quenching too. A number of degradation products were identified-for example, alclehydes and organic acids-which were present in homologous series. The total amount of aldehydes and acids for each number of chain carbon atoms were appeared in the order of C5>C4>C6>C7much greater thanC2 for LDPE, C5>C6>C4> C7much greater thanC2 for LLDPE, and C5>C6>C7>C4much greater thanC2 for HDPE. The total amounts of oxidized compounds presented in the films were related to the processing conditions. Polymer melts exposed to oxygen at the highest temperatures and longest times showed the presence dialdehydes, in addition to the aldehydes and acids. (C) 2003 Wiley Periodicals, Inc. J Appl Polyrn Sci 91: 1525-1537, 2004. (Less)
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author
organization
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Contribution to journal
publication status
published
subject
in
Journal of Applied Polymer Science
volume
91
issue
3
pages
1525 - 1537
publisher
John Wiley & Sons
external identifiers
  • wos:000187712400020
  • scopus:1642503781
ISSN
1097-4628
DOI
10.1002/app.13024
language
English
LU publication?
yes
id
3ca4173a-ba25-465d-b4d0-f380efc1a691 (old id 139553)
date added to LUP
2007-07-12 15:30:14
date last changed
2017-10-01 03:52:05
@article{3ca4173a-ba25-465d-b4d0-f380efc1a691,
  abstract     = {The degradation of different polyethylenes-low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE)-with and without antioxidants and at different oxygen concentrations in the polymer granulates, have been studied in extrusion coating processing. The degradation was followed by online rheometry, size exclusion chromatography, surface oxidation index measurements, and gas chromatography-mass spectrometry. The degradations start in the extruder where primary radicals are formed, which are subject to the auto-oxidation when oxygen is present. In the extruder, crosslinking or chain scissions reactions are dominating at low and high melt temperatures, respectively, for LDPE, and chain scission is overall dominating for the more linear LLDPE and HDPE resins. Additives such as antioxidants react with primary radicals formed in the melt. Degradation taking place in the film between the die orifice, and the quenching point is mainly related to the exposure time to air oxygen. Melt temperatures above 280degreesC give a dominating surface oxidation, which increases with the exposure time to air between die orifice and quenching too. A number of degradation products were identified-for example, alclehydes and organic acids-which were present in homologous series. The total amount of aldehydes and acids for each number of chain carbon atoms were appeared in the order of C5>C4>C6>C7much greater thanC2 for LDPE, C5>C6>C4> C7much greater thanC2 for LLDPE, and C5>C6>C7>C4much greater thanC2 for HDPE. The total amounts of oxidized compounds presented in the films were related to the processing conditions. Polymer melts exposed to oxygen at the highest temperatures and longest times showed the presence dialdehydes, in addition to the aldehydes and acids. (C) 2003 Wiley Periodicals, Inc. J Appl Polyrn Sci 91: 1525-1537, 2004.},
  author       = {Andersson, T and Stalbom, B and Wesslén, Bengt},
  issn         = {1097-4628},
  language     = {eng},
  number       = {3},
  pages        = {1525--1537},
  publisher    = {John Wiley & Sons},
  series       = {Journal of Applied Polymer Science},
  title        = {Degradation of polyethylene during extrusion. II. Degradation of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene in film extrusion},
  url          = {http://dx.doi.org/10.1002/app.13024},
  volume       = {91},
  year         = {2004},
}