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Isotactic Poly(propylene) Crystallization: Role of Small Fractions of High or Low Molecular Weight Polymer
Author(s) -
Elmoumni Aadil,
GonzalezRuiz Ramon A.,
Coughlin E. Bryan,
Winter H. Henning
Publication year - 2005
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200400130
Subject(s) - crystallization , tacticity , polymer , materials science , polymer chemistry , mass fraction , micrograph , shearing (physics) , chemical engineering , polymerization , crystallography , chemistry , composite material , scanning electron microscope , engineering
Summary: Two well‐characterized metallocene isotactic poly(propylene) (iPP) samples, one of high and one of low molecular weight, were blended together for studying the effects of a second component on quiescent and shear‐induced crystallization. A small amount of added high molecular weight (HMW) (up to 10 wt.‐%) polymer increases the quiescent crystallization rate. This was observed as a decrease in characteristic halftime of transmitted light intensity. The crystallization halftime increases again when adding more than 10 wt.‐% of HMW polymer. The crystallization halftime of pre‐sheared samples decreases with increasing HMW fraction and is lowest for the HMW sample by itself. For the specific shearing conditions ( γ = 600, T x = 145 °C), wide‐angle X‐ray diffraction (WAXD) images show the presence of the gamma ( γ ) crystalline phase of iPP for samples containing 25 wt.‐% of HMW and higher. DSC thermograms demonstrated higher crystalline fractions with increasing HMW fraction in pre‐sheared samples.Optical micrograph of an iPP sample after quiescent crystallization at 145 °C.