HDPE liquefaction: Random chain scission model

Priya Rangarajan, Dibakar Bhattacharyya, Eric Grulke

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Liquefaction of commodity polymers to oils and gases can be used to recover the energy value of these materials. This article reports liquefaction data for high-density polyethylene (HDPE), one of the major plastics in recycled material. Thermal degradation of HDPE to oil-gas mixtures required higher temperatures (450-490 °C) than low-density polyethylene (LDPE) (430-460 °C) because of fewer chain branching points for HDPE, which are more susceptible to chain scission reactions. The addition of hydrogen (0.1-1.5 MPa) had negligible effect on product distribution. HDPE thermal degradation is consistent with a random chain scission mechanism. Product distributions for degradation at 450 °C were modeled assuming random chain scission with a rate constant k(x) dependent on the molecular weight x by a power law model dependence, k(x) = kb xb, where kb is the pseudo-first-order rate constant, and b is the power index of dependence on molecular weight. Degradation rates dropped rapidly after initial breakup of the chains, and 2 sets of coefficients were needed to describe the molecular weight distributions as functions of reaction time. The error in model was about 10%. This model can be used to optimize the production of oils from thermal degradation of HDPE.

Original languageEnglish
Pages (from-to)1239-1251
Number of pages13
JournalJournal of Applied Polymer Science
Issue number6
StatePublished - Nov 7 1998

ASJC Scopus subject areas

  • General Chemistry
  • Surfaces, Coatings and Films
  • Polymers and Plastics
  • Materials Chemistry


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