Effects of melt reprocessing on volatile emissions and structural/rheological changes of unstabilized polypropylene

Q. Xiang, M. Xanthos, S. Mitra, S. H. Patel, J. Guo

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49 Scopus citations


Emission of volatile organic compounds (VOCs) during multiple melt reprocessing of polypropylene (PP) was studied in this research. An unstabilized commercial grade polypropylene (PP) was processed several times by injection molding to simulate multiple recycling. After each cycle, the PP was non-isothermally heated in a reactor, and the total VOCs emissions were monitored using a flame ionization detector (FID). Cumulative VOCs emissions versus cycle number showed an almost linear relationship. Corresponding structural changes were investigated using Fourier Transform Infrared (FTIR) Spectroscopy, and the results were correlated with rheological properties via melt flow index measurement. The data showed a decrease in viscosity, particularly after the 7th processing cycle. A simulation study was performed by multiple heating and cooling of a single PP sample under static conditions, and in different gaseous (nitrogen, oxygen, air) atmospheres. The results indicate that the actual reprocessing conditions generate emissions whose levels, and the rate of generation are closer to mild thermooxidative degradation rather than a pure thermal degradation.

Original languageEnglish (US)
Pages (from-to)93-102
Number of pages10
JournalPolymer Degradation and Stability
Issue number1
StatePublished - 2002

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Polymers and Plastics
  • Materials Chemistry


  • Degradation
  • Emissions
  • Polypropylene
  • Reprocessing
  • Volatile organic compounds


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