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Thermophysical Properties and Molecular Relaxations in Cured Epoxy Resin + PEO Blends: Observations on Factors Controlling Miscibility
Author(s) -
Kalogeras Ioannis M.,
VassilikouDova Aglaia,
Christakis Iraklis,
Pietkiewicz Dorota,
Brostow Witold
Publication year - 2006
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.200600052
Subject(s) - miscibility , glass transition , materials science , epoxy , diglycidyl ether , amorphous solid , polymer blend , polymer chemistry , ethylene oxide , thermosetting polymer , relaxation (psychology) , polymer , bisphenol a , chemical engineering , composite material , chemistry , organic chemistry , copolymer , psychology , social psychology , engineering
Abstract Summary: Thermophysical properties and molecular relaxations in aromatic amine‐cured diglycidyl ether of bisphenol‐A (DGEBA) epoxy oligomer and poly(ethylene oxide) (PEO) mixtures were determined by DSC and dielectric techniques (TSC, DRS). The binary blends were judged to be fully miscible in the amorphous state ( w PEO < 40 wt.‐%), as evidenced by the single composition‐dependent glass transition temperatures T g s. In the amorphous blends, negative deviations of dielectric/thermal T g ‐estimates from the linear mixing rule or the behavior predicted by the Fox equation reveal weaker intermolecular interactions, compared to strong self‐association of hydroxyls in the cured thermoset. Morphological changes in PEO‐rich blends ( w PEO ≥ 40 wt.‐%) are in accordance with their complicated interface structure, previously reported to consist of amorphous PEO regions, branched epoxy resin chains and an imperfect epoxy resin network located between PEO lamellae. In these blends, PEO crystallites exert steric hindrances in the amorphous regions, causing strong T g upshifts. Changes in the relaxation dynamics of glyceryl segments (e.g., in the activation energy barrier and relaxation strength) are in accordance with the idea that the close matching between the molecular polarities of PEO, epoxy resin and the cure agent significantly contributes to the observed miscibility.Plots of transition temperatures as function of blend composition.