DSC was used to study the changes of enthalpy relaxation behavior of blends of poly (2

6-dimethyl-1

4-phenylene oxide) (PPO)and benzoylated PPO(31. 0 mol% and 43. 3 mol% of benzoyl group respectively) (BA31.0-PPO

BA43.4-PPO). It was found that for the miscible blend of BA31.0-PPO/PPO

there was only one endothermal peak during the isothermal annealing. This behavior was very similar to that of PPO/PS blend. But for the BA43.4-PPO/ PPO blend whose miscibility was unknown

there were two endothermal peaks during the an-nealing

and the Tg values of the two peaks were very close to those of pure components of BA43.4-PPO or PPO. The results of SEM micrographs indicated that BA43.4-PPO/PPO was two phase system. So the enthalpy relaxation can be used to study the compatible properties of blend of PPO and its derivatives which have similar Tg.