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Colloid and Polymer Science

, Volume 273, Issue 2, pp 130–137 | Cite as

A quantitative model describing physical aging in isotactic polypropylenes

  • S. Hellinckx
Original Contribution

Abstract

Physical aging of isotactic polypropylenes (homopolymer and random ethylene-propylene copolymer) at room temperature is investigated by low-strain creep, damping measurements, differential scanning calorimetry, and infra-red spectroscopy. Examination of the results suggests that physical aging produces a decrease of the magnitude of the β-relaxation (lower glass transition) and an increase of the magnitude and of the relaxation time of the α-relaxation (upper glass transition). A model is proposed that accounts for the variations of the fractions of amorphous material which undergo these relaxations. In this model, deformation and increase in the α-fraction at the expense of the β-fraction are expected to be diffusion processes. The agreement with experimental data is good. Moreover, the α-form is shown to be an amorphous phase rich in molecular segments having a helical conformation.

Key words

Isotactic PP physical aging low-strain creep magnitude of β and α relaxations amorphous forms 

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Copyright information

© Steinkopff-Verlag 1995

Authors and Affiliations

  • S. Hellinckx
    • 1
  1. 1.Physique des Matériaux de Synthèse 194/8Université Libre de BruxellesBruxellesBelgium

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