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1479597 
Journal Article 
Viscoelastic effects in thermoplastic poly(styrene-acrylonitrile)-modified epoxy-DDM system during reaction induced phase separation 
Jyotishkumar, P; Moldenaers, P; George, SM; Thomas, S 
2012 
1 
Soft Matter
ISSN: 1744-683X 
8 
28 
7452-7462 
WOS:000305764800018 
The viscoelastic phase separation of a poly(styrene-co acrylonitrile) (SAN) modified epoxy system based on the diglycidyl ether of bisphenol A (DGEBA)
cured with 4,4'-diaminodiphenylmethane (DDM) has been monitored in situ using rheometry, optical
microscopy (OM) and small angle laser light scattering (SALLS). The amount of SAN in the epoxy
blends were 3.6, 6.9, 10, and 12.9 wt%. The relationship between rheological properties and phase
separation was carefully explored. The evolution of storage modulus, loss modulus, and tan delta
were found to be closely related to the evolution of complex phase separation. From the
rheological profile, two gel points are identified, corresponding to physical gelation and
chemical gelation, the first one because of viscoelastic phase separation and the second one
related to crosslinking of the epoxy resin, these depend on the cure temperature and amount of
thermoplastic. Further SALLS investigations investigated the mechanism of phase separation. The
time-dependent peak scattering vector was simulated with a Maxwell-type viscoelastic relaxation
equation. Relaxation times obtained at different temperatures for the blends could be described
by the Williams-Landel-Ferry equation. Moreover, the development of light scattering profile
follows the Tanaka model of viscoelastic phase separation.