Thermal properties and morphologies of different thermoplastic polymers blended with an elastomer are discussed. Poly(ethylene terephthalate) (PET), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 12%mole of hydroxyvalerate content (PHBV) and poly(ethylene oxide) (PEO) were blended with epoxidized natural rubber (ENR). These blends turn out to be immiscible. Degree of crystallinity after isothermal crystallization and equilibrium melting point of the crystallizable constituents stay constant to a good approximation in blends with ENR. Exponential decay of rate of crystallization could be observed for both neat polymers and blends. Morphology formation was observed under condition of constant rate of crystallization, which is concomitantly related to different distances to equilibrium. It turns out that morphology development in the blends reflects both aspects. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 1774-1781, 2011