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Shear influence on the phase behavior of systems containing a homopolymer A and a block copolymer AB
Author(s) -
Madbouly Samy A.
Publication year - 2003
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200350805
Subject(s) - materials science , crystallization , shear rate , nucleation , thermodynamics , isothermal process , rheometer , ethylene oxide , ternary operation , kinetics , upper critical solution temperature , copolymer , chemical engineering , polymer chemistry , composite material , rheology , polymer , lower critical solution temperature , physics , quantum mechanics , computer science , engineering , programming language
Cloud point temperatures ( T cp ) and crystallization temperatures ( T l/s ) of the ternary system tetrahydronaphthalene/poly(ethylene oxide)/poly(dimethyl siloxane‐ b ‐ethylene oxide) have been measured at different constant shear rates using a rheo‐optical device and an advanced rheometer. The cloud points temperatures (UCST‐type phase diagram) are reduced by several degrees as the system flows; i.e. the shear can suppress the phase separation and enlarge the homogenous region. The crystallization kinetics of PEO in the ternary mixtures has been investigated isothermally and non‐isothermally at quiescent state and under shear. The shear could strongly enhance the crystallization i.e. the ( T l/s ) shifts to higher temperatures and the induction time, t 0 (the time needs for the onset of crystallization) substantially decreases with increasing shear rate during the non‐isothermal and isothermal crystallization processes, respectively. The isothermal crystallization kinetics at quiescent state and at different shear rates was analyzed on the bases of Avrami approach. The Avrami exponent which provides qualitative information about the nature of the nucleation and growth process, was found to be shear rate and temperature dependent. The Avrami exponent increased from ∼3 at the quiescent state to as large as 9 at &&ggr;dot; = 100 s −1 .

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