Crystallization of Isotactic Polypropylene under High Pressure (γ Phase)

Isothermal crystallization of isotactic polypropylene at high pressures (from 200 to 250 MPa) have been carried out using a high-pressure dilatometer leading to a pure γ-form, as revealed by WAXD. The melting temperatures at the same pressures have been determined to assess the pressure effect on th...

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Bibliographic Details
Published in:Macromolecules 2000-05, Vol.33 (11), p.4138-4145
Main Authors: Angelloz, C, Fulchiron, R, Douillard, A, Chabert, B, Fillit, R, Vautrin, A, David, L
Format: Article
Language:English
Subjects:
Condensed Matter
Materials Science
Physics
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Summary:Isothermal crystallization of isotactic polypropylene at high pressures (from 200 to 250 MPa) have been carried out using a high-pressure dilatometer leading to a pure γ-form, as revealed by WAXD. The melting temperatures at the same pressures have been determined to assess the pressure effect on the equilibrium melting temperature by the Hoffman−Weeks analysis. The crystallization times have been analyzed according to the Hoffman−Lauritzen theory and corrections introduced to take into account the pressure effects on both the equilibrium melting temperature and the diffusion process. This analysis showed a transition from crystallization regime II to regime III for an undercooling of 53.7 K. The lateral and fold surface free energies were evaluated. Furthermore, the morphology of the samples investigated by polarized light microscopy, density measurements, and SAXS depends only on the crystallization undercooling, as a result of the influence of pressure on the equilibrium melting temperature. Moreover, the lamellar thickness experimental data agree well with the theoretical calculation.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma991813e