Elastomer-modifying is often used to improve the mechanical properties of epoxy resins

and the epoxy resin(EP)／thermoplastic polyurethane(TPU) is a fairly effective system．In this article the phase behavior of EP/TPU blends was investigated by time-resolved small angle light scattering (SALS) analysis．The correlation distance (ac) and mean square dielectric constant fluctuation (η) of EP/TPU blends were calculated．Evolutions of the domain size in EP／TPU blends were discussed under the isothermal curing condition．The results showed that the cured process of EP/TPU was a typical spinodal decomposition and can be well described by Cahn-Hilliard linearized theory at the early stage．With the cure development

the domains grew up and kept constant after 60 min．During the early blend cure process

the correlation distance (ac) and mean square dielectric constant fluctuation (η) of EP／TPU blends increased rapidly．from 0 to 1.00 and 0 to 118

respectively

if the experimental time was from 145 s to 1080 S．After that

the domains of the blends began to coalesce resulting in the decrease of η and increase ofac

which will keep constant after 3210 s when ac and η are 1.30 and 32

respectively．