Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Longterm performance of polyolefins in different environments including chlorinated water: antioxidant consumption and migration and polymer degradation
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The long-term performance of stabilized polyolefins in different environments was studied with focus on antioxidant consumption and migration. Plaques of linear polyethylene (LPE) and branched polyethylene (BPE) were stabilized with Santonox® R (4,4'-Thiobis(6-tert-butyl-3-methylphenol)), Irganox® 1081 (2,2’-Thiobis(4-methyl-6-tertbutylphenol)), or Lowinox® 22M46 (2,2’-Methylenebis(6-tert-butyl-4-methylphenol)). The samples were aged in water and nitrogen at 75, 90 and 95°C. Antioxidant concentration profiles were obtained by oxidation induction time (OIT) measurements using differential scanning calorimetry (DSC). The very flat antioxidant concentration profiles of the plaques exposed to non-aqueous media indicated that the migration of antioxidant to the surrounding medium was controlled by the low evaporation rate at the sample boundary. The samples of BPE and Santonox R were also exposed to air and water saturated with air. The similarity of the antioxidant concentration profiles of Santonox R obtained after ageing in air and nitrogen suggested that the fraction of antioxidant oxidized is negligible in comparison with the loss of antioxidant by migration to the surrounding media. The loss of Santonox R in samples exposed to water saturated with air was faster than for the samples exposed to oxygen-free water. This was due to increased mass transport of the antioxidant from the polymer phase boundary to the water phase when oxygen was present. An unexpected higher migration rate from LPE than from BPE was proposed to be due to the low boundary loss rate in BPE, caused by the presence of a thin liquid-like (oligomeric) surface layer developed during ageing. A quantitative relationship was found between the boundary loss rate to water and the polarity of antioxidants. The antioxidant diffusivities were approximately equal in LPE and BPE, indicating that the constraining effect of the crystals on the non-crystalline fraction did not affect the antioxidant molecules. Results obtained by liquid chromatography of extracts confirmed that the gradual decrease in OIT with increasing ageing time was due to migration of antioxidant to the surrounding medium. Pipes of high-density polyethylene stabilized with hindered phenols and phosphites were exposed to chlorinated water at elevated temperatures. OIT showed that the stabilizing system was rapidly chemically consumed by the action of chlorinated water. Size exclusion chromatography and DSC showed extensive polymer degradation strictly confined to the immediate surface of the unprotected inner wall material and to the amorphous phase of the semicrystalline polymer. The rate of growth of the layer of highly degraded polymer was constant. Pipes of isotactic polybutene-1 were pressure-tested in chlorinated water at a controlled pH, and the lifetime was assessed as a function of temperature and chlorine content. The lifetime shortening in chlorinated water was significant even at relatively low chlorine contents, 0.5 ppm. A further increase of chlorine content led to only a moderate shortening of the lifetime. The temperature dependence of the lifetime data obeyed the Arrhenius law. The decrease of the antioxidant concentration was independent of the chlorine concentration in the range of 0.5-1.5 ppm. The time to reach depletion of the antioxidant system could be predicted by linear extrapolation.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 45 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:15
Keyword [en]
Chemical engineering, polyethylene, polybutylene, HDPE, LLDPE, phenolic antioxidants, oxidation induction time(OIT), migration, chlorinated water, pressure testing, lifetime, chemical consumption.
Keyword [sv]
Kemiteknik
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-238ISBN: 91-7178-095-5 (print)OAI: oai:DiVA.org:kth-238DiVA: diva2:8015
Public defence
2005-06-16, K2, Teknikringen 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20101020Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2010-10-20Bibliographically approved
List of papers
1. Loss of stability by migration and chemical reaction of Santonox R in branched polyethylene under anaerobic and aerobic conditions
Open this publication in new window or tab >>Loss of stability by migration and chemical reaction of Santonox R in branched polyethylene under anaerobic and aerobic conditions
Show others...
2006 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 5, 1071-1078 p.Article in journal (Refereed) Published
Abstract [en]

Plaques of branched polyethylene stabilized with 0.1 wt.% 4,4′-thiobis(6-tert-butyl-3-methylphenol) [Santonox® R] were aged at different temperatures between 75 and 95°C in anaerobic (nitrogen or water) and aerobic (air or water saturated with air) media. Antioxidant concentration profiles were obtained by oxidation induction time (OIT) measurements using differential scanning calorimetry. Results obtained by high performance liquid chromatography of extracts confirmed that the gradual decrease in OIT with increasing ageing time was due to migration of antioxidant to the surrounding medium. The antioxidant concentration profiles along the plaque thickness direction were flat in the plaques aged in the non-aqueous media indicating that the migration of antioxidant to the surrounding medium was controlled by the low evaporation rate at the material boundary. Crystals of antioxidant were detected by optical microscopy on the samples exposed to nitrogen. The similarity of the antioxidant concentration profiles obtained after ageing in nitrogen and in air suggested that the fraction of the antioxidant oxidized is negligible in comparison with the loss of antioxidant by migration to the surrounding media. The antioxidant concentration profiles along the plaque thickness direction obtained after ageing in water were less flat, suggesting faster dissolution in the water phase than evaporation in the case of non-aqueous ageing. The antioxidant diffusivity could be determined from the aqueous experiments and was in reasonable agreement with data reported by Moisan. For the samples exposed to water, the loss of antioxidant was faster from the samples exposed to water saturated with air. This difference is attributed to a faster degradation of the antioxidant in the oxygen-containing water phase increasing the mass transport from the polymer phase boundary to the water phase.

Keyword
Branched polyethylene, Chemical consumption, Migration, Santonox R
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5196 (URN)10.1016/j.polymdegradstab.2005.07.010 (DOI)000236076400011 ()2-s2.0-31444445573 (Scopus ID)
Note
QC 20100921. Uppdaterad från Submitted till Published (20100921).Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2017-12-04Bibliographically approved
2. Migration of phenolic antioxidants from linear and branched polyethylene
Open this publication in new window or tab >>Migration of phenolic antioxidants from linear and branched polyethylene
2006 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 7, 1571-1580 p.Article in journal (Refereed) Published
Abstract [en]

Plaques of linear polyethylene (LPE) and branched polyethylene (BPE) were exposed to oxygen-free media (nitrogen or water) at 75, 90 and 95 degrees C. The polymers were stabilized with one of the following three bifunctional phenolic antioxidants: Santonox R, Irganox 1081 or Lowinox 22M46. The initial concentration of antioxidant in the plaques was similar to 0.09 wt.%. After ageing, the oxidation induction time profiles obtained by differential scanning calorimetry often became very flat, which indicated that migration was controlled by the boundary loss process. The unexpected higher migration rate from LPE than from BPE was due to the dominance of the boundary loss process. It is proposed that the low boundary loss rate in BPE was due to the presence of a thin liquid-like (oligomeric) surface layer which developed during ageing of this polymer. A qualitative relationship was found between the boundary loss rate to water and the polarity of the antioxidant. The antioxidant diffusivities in LPE and BPE were approximately equal, a finding which, in view of the morphological analysis estimating the geometrical impedance factor, indicated that the constraining effect of the crystals on the non-crystalline fraction was not sensed by the antioxidant molecules. It is suggested that the large molecular size and the low segmental flexibility of the antioxidant molecules inhibited their ability to penetrate the interfacial component.

Keyword
polyethylene, migration, phenolic antioxidants, morphology
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5197 (URN)10.1016/j.polymdegradstab.2005.09.008 (DOI)000237776100019 ()2-s2.0-33645133017 (Scopus ID)
Note
QC 20100922. Uppdaterad från Submitted till Published (20100922).Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2017-12-04Bibliographically approved
3. Polybutene-1 pipes exposed to pressurized chlorinated water: lifetime and antioxidant consumption
Open this publication in new window or tab >>Polybutene-1 pipes exposed to pressurized chlorinated water: lifetime and antioxidant consumption
2006 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 4, 842-847 p.Article in journal (Refereed) Published
Abstract [en]

Pipes of isotactic polybutene-1 were pressure-tested in chlorinated water at a controlled pH (6.5 ± 0.1), and the lifetime was assessed as a function of temperature (95-115°C) and chlorine content (≤3 ppm). These data were compared with data from pressure testing in hot water (0 ppm chlorine). The lifetime shortening in chlorinated water was significant even at relatively low chlorine contents, 0.5 ppm. A further increase in chlorine content led only to a moderate shortening of the lifetime. The temperature dependence of the lifetime data obeyed the Arrhenius law. The activation energy obtained for failure data in chlorinated water was ∼140 kJ mol-1, which was greater than the value of 108 kJ mol-1 earlier reported for failure data from hot-water pressure testing. A 0.5-mm thick layer of material at the inner wall in the fractured pipes showed depletion of the antioxidant system and the inner wall displayed a large number of surface cracks, confirming that there was a pronounced chemical degradation of the inner wall material. The decrease in the antioxidant concentration was independent of the chlorine concentration in the range 0.5-1.5 ppm. The time to reach depletion of the antioxidant system could be predicted by linear extrapolation in an oxidation induction time (log scale)-exposure time (linear scale) diagram.

Keyword
Antioxidant, Chlorinated water, Lifetime, Polybutene-1, Pressure testing
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5198 (URN)10.1016/j.polymdegradstab.2005.06.015 (DOI)000234948300026 ()2-s2.0-30144439560 (Scopus ID)
Note
QC 20100927. Uppdaterad från Submitted till Published (20100927).Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2017-12-04Bibliographically approved
4. Deterioration of polyethylene pipes exposed to chlorinated water
Open this publication in new window or tab >>Deterioration of polyethylene pipes exposed to chlorinated water
2004 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 84, no 2, 261-267 p.Article in journal (Refereed) Published
Abstract [en]

Pipes of high-density polyethylene were exposed to chlorinated water at elevated temperatures. The materials were stabilised with hindered phenols and phosphites. Oxidation induction times measured by DSC showed that the stabilising system was rapidly chemically consumed by the action of chlorinated water. Size exclusion chromatography and DSC showed extensive polymer degradation strictly confined to the immediate surface of the unprotected inner wall material and to the amorphous phase of the semicrystalline polymer. The rate of growth of the layer of highly degraded polymer was constant. It is obvious from the data that the species responsible for the loss of antioxidant are soluble in the polymer but not very reactive with the polymer itself. The species responsible for polymer degradation, on the other hand, are very reactive with the polymer and/or have a very low solubility in the polymer.

Keyword
polyethylene pipes, chlorinated water, degradation, chlorine
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5199 (URN)10.1016/j.polymdegradstab.2003.10.019 (DOI)000222122300009 ()2-s2.0-2542471916 (Scopus ID)
Note
QC 20100908Available from: 2005-05-31 Created: 2005-05-31 Last updated: 2017-12-04Bibliographically approved

Open Access in DiVA

fulltext(5379 kB)9102 downloads
File information
File name FULLTEXT01.pdfFile size 5379 kBChecksum MD5
098eca971a8913549ca8490bc2029d99dc49ffcf4992bc63ab4c8ebcbebe0d7de37bfef9
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Lundbäck, Marie
By organisation
Fibre and Polymer Technology
Chemical Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 9102 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1588 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf