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
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.
Place, publisher, year, edition, pages
2006. Vol. 91, no 7, 1571-1580 p.
polyethylene, migration, phenolic antioxidants, morphology
IdentifiersURN: urn:nbn:se:kth:diva-5197DOI: 10.1016/j.polymdegradstab.2005.09.008ISI: 000237776100019ScopusID: 2-s2.0-33645133017OAI: oai:DiVA.org:kth-5197DiVA: diva2:8012
QC 20100922. Uppdaterad från Submitted till Published (20100922).2005-05-312005-05-312010-09-22Bibliographically approved