Polymer composites of PLA/PTT matrix blended with a small amount of 1, 3 wt% maleic anhydride-grafted polyethylene-octene (mPOE) or organically-modified nanoclay (Cloisite 30B) were prepared by the melt mixing method. The rheological measurements were conducted using the oscillatory rheometer. The stress relaxation time, which is inversely proportional to the cross-over frequency for the curves of the storage and loss moduli, can be estimated with the frequency sweep in the dynamic tests. It can be found that the complex viscosity (with strong shear-thinning), storage and loss moduli grew up with the increasing amount of PTT (20, 30, 50 wt%) and either one of the above fillers loaded. The relaxation time of the neat PLA/PTT blend was getting longer as more PTT was added. As to the PLA/PTT composites, a small amount of filler (irrespective of mPOE or Cloisite 30B) added could make the relaxation times become small; addition of 3 % nanoclay could make the relaxation time 100-fold shorter than that of the neat PLA/PTT blend. The flow activation energy was calculated, using the Arrhenius equation, with the temperature sweep of the complex viscosity in the dynamic measurements. It was found the activation energy of PTT was increased as its composition in the PLA/PTT blends was raised. For the PLA/PTT/clay nanocomposite, the addition of 1% Cloisite 30B may cause the activation energy contributed by PTT become very high; on the contrary, 3% addition of Cloisite 30B reduced the activation energy of the PTT phase, even lower than that of the neat PTT.
