Premium
Study of crystallization and melting behavior of polypropylene‐ block ‐polyethylenes copolymers fractionated from polypropylene and polyethylene mixtures
Author(s) -
Xu JunTing,
Ding PingJing,
Fu ZhiSheng,
Fan ZhiQiang
Publication year - 2004
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1519
Subject(s) - polypropylene , materials science , polyethylene , crystallinity , copolymer , crystallization , polymer chemistry , ethylene , isothermal process , chemical engineering , polymerization , composite material , polymer , thermodynamics , chemistry , organic chemistry , catalysis , physics , engineering
A series of ethylene–propylene block copolymer fractions of differing compositions, while still retaining broad molecular weight distributions, were obtained by fractionation of polypropylene (PP) and polyethylene (PE) copolymers prepared by sequential polymerization of ethylene and propylene. The crystallization and melting behavior of the polypropylene‐ block ‐polyethylene fractions were studied. It was observed that the major component could suppress crystallization of the minor component, leading to a decrease in crystallinity and melting temperature. Non‐isothermal crystallization showed that crystallization of the ethylene block was less influenced by composition and cooling rate than the propylene block. At fast cooling rates, the ethylene block could crystallize prior to the propylene block. Isothermal crystallization kinetics experiments were also conducted. We found that the block copolymers with minor ethylene components had smaller Avrami exponents ( n ≈ 1.0), hence indicating a reduced growth dimension of the PE crystals by the pre‐existing PP crystals. On the other hand, the ethylene block exhibited much larger Avrami exponents in those block copolymers with major ethylene contents. Copyright © 2004 Society of Chemical Industry