Crystallization kinetics and morphology of poly(propylene-stat-ethylene) fractions.
1997 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 38, no 2, 361-369 p.Article in journal (Refereed) Published
The crystallization and melting behaviour and the morphology of fractions of poly(propylene-stat-ethylene) with 2.7–11.0 mol% ethylene were studied by differential scanning calorimetry, wide-angle X-ray scattering, polarized light microscopy and transmission electron microscopy, after etching with permanganic acid. The inclusion of ethylene co-repeating units in isotactic polypropylene (0–11.0 mol% ethylene) caused approximately linear decreases in kinetic and equilibrium melting temperatures and in the glass transition temperature with increasing ethylene content. X-ray scattering showed that the content of the γ form increased with increasing ethylene content, increasing crystallization temperature and decreasing cooling rate from the molten state. It was shown for one of the copolymers (8.7 mol% ethylene) that during heating approximately 50% of the γ form was converted to the α form before the final melting of the sample. The rest of the γ crystals melted without transformation to the α form. The multimodality of the crystal melting above the crystallization temperature in the polymers with a more uniform crystal structure was caused by recrystallization during heating, whereas polymers with appreciable contents of both α and γ forms exhibited multimodal melting at all the heating rates adopted. The size of the low temperature melting peak as assessed at a heating rate of 40 K min−1 was approximately proportional to the initial content of the γ form. By comparison with the spherulitic structure of homopolymers, that of the copolymers was coarser with internal and peripheral pockets of molten material during spherulite growth. The crystal lamellae exhibited more curvature in the copolymer samples than in the homopolymer.
Place, publisher, year, edition, pages
1997. Vol. 38, no 2, 361-369 p.
poly(propylene-stat-ethylene), fractions, melting
IdentifiersURN: urn:nbn:se:kth:diva-5301DOI: 10.1016/S0032-3861(96)00502-2ISI: A1997WD22400013OAI: oai:DiVA.org:kth-5301DiVA: diva2:8362
QC 201010272005-06-072005-06-072010-10-27Bibliographically approved