Relationship between breakdown of time-temperature superposition principleand phase-separation for PMMA/alpha-MSAN blends

By examining superposition of viscoelastic functions of poly(methyl methacr ylate) (PMMA)/poly (alpha-methylstyrene-co-acrylonitrile) (alpha-MSAN) blen ds, we found that breakdown of time-temperature superposition principle in the long time relaxation region (terminal region) is related to phase-separ ation of this blends. Heterogeneity in the blends results in the relationsh ip between dynamic storage modulus G' (or dynamic loss modulus G ") and fre quency omega in the terminal region no longer obey the model of linear visc oelasticity. It is interesting that there exists temperature dependence of this breakdown. This "breakdown temperature"(rd) can be used as a criterion for phase-separation of the blends and was considered superior to so-calle d "critical temperature" (T-b) obtained by plotting of lgG' vs, lgG ".