Crystal structure and morphology of melt-crystallized poly(propylene-stat-ethylene) fractions.
1997 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 38, no 2, 371-377 p.Article in journal (Refereed) Published
Crystallinity, crystal structure and lamellar thickness in melt-crystallized samples of poly(propylene-stat-ethylene) fractions with 2.7–11.0 mol% ethylene comonomer and of approximately constant tacticity were assessed by wide- and small-angle X-ray scattering, differential scanning calorimetry and infra-red spectroscopy. Most of the samples were crystallized under isothermal conditions at 373 K. In comparison with an isotactic homopolymer of polypropylene, the copolymers showed lower crystallinity, melting enthalpy and average length of 3/1 helices, a slightly larger unit cell, a longer long period and an invariant lamellar thickness. The X-ray crystallinity of the copolymers remained approximately constant with increasing ethylene content, whereas the γ-crystallinity increased and the heat of fusion decreased moderately. It is suggested that the ethylene units are partially included in the crystals, and that this causes the invariance in crystallinity and crystal thickness. The observed gradual decrease in average 3/1 helix length with increasing ethylene content as assessed by infra-red spectroscopy is in accordance with this suggestion.
Place, publisher, year, edition, pages
1997. Vol. 38, no 2, 371-377 p.
poly(propylene-stat-ethylene), X-ray scattering, thermal analysis
IdentifiersURN: urn:nbn:se:kth:diva-5300DOI: 10.1016/S0032-3861(96)00503-4OAI: oai:DiVA.org:kth-5300DiVA: diva2:8361
QC 201010272005-06-072005-06-072010-10-27Bibliographically approved