Cc. Riccardi et al., THERMODYNAMIC ANALYSIS OF THE PHASE-SEPARATION IN POLYETHERIMIDE-MODIFIED EPOXIES, Journal of polymer science. Part B, Polymer physics, 34(2), 1996, pp. 349-356
The miscibility of polyetherimides (PEIs) with epoxy monomers based on
diglycidylether of bisphenol-A (DGEBA), and with reactive mixtures ba
sed on stoichiometric amounts of DGEBA and an aromatic diamine (DA) {e
ither 4,4'-diaminodiphenylsulfone (DDS) or 4,4'-methylenebis[3-chloro
2,6-diethylaniline] (MCDEA)}; was experimentally studied. Cloud-point
curves (temperature vs. composition) are reported for PEI-DGEBA and PE
I-DGEBA-DA initial mixtures. Cloud-point conversions are reported for
the reactive mixtures, for various PEI amounts and polycondensation te
mperatures. A thermodynamic model based on the Flory-Huggins-Staverman
approach, taking polydispersity of both components into account, was
used to analyze the experimental information. A single relationship be
tween the interaction parameter and temperature, chi(T), could fit exp
erimental results of mixtures of two commercial PEIs with DGEBA. The a
ddition of DDS led to a decrease in miscibility whereas MCDEA improved
the initial miscibility. In both cases, the interaction parameter dec
reased with conversion, meaning that PEI was more compatible with olig
omeric species than with the mixture of starting monomers. The phase s
eparation process in initially miscible rubber- or thermoplastic-modif
ied thermosetting polymers is the result of two factors: increase in t
he average molar size of the thermosetting oligomer (main driving forc
e favoring demixing), and variation of the interaction parameter with
conversion, which may act to increase or decrease the cloud-point conv
ersion determined by the first factor. (C) 1996 John Wiley & Sons, Inc
.