In this study, the rheological and morphological behavior of Polypropylene/ Polyethylene Terephthalate immiscible polymer blend has been investigated, in presence of silica aerogel nanostructure compatibilizer. The nitrogen adsorption-desorption test on silica aerogel nanostructure confirmed the formation of a mesoporous structure with a narrow pore size distribution. FTIR spectrum of nanocomposites PET/hydrophilic silica aerogel is shown that there is no chemical interaction between silica aerogel particles and PET matrix. The XRD patterns showed that the hydrophilic particles have little effect on changing the crystalline structure of PP/PET polymer blend. The SEM images of nanocomposites filled by silica aerogel particles reveal the presence of silica aerogel particles in a PP/PET polymer blend significantly reduces droplets size of PET dispersed phase and cohesion of droplets. The wetting parameter of PP/PET polymer blend in presence of hydrophilic silica aerogel was found to be less than -1. According to this value, the particles tend to locate in PET dispersed phase of the blend. During the investigation of complex viscosity, it was observed a 49% mutation in the specimen contains 0.2 phr of hydrophilic silica aerogel in comparison of the pure specimen. This corresponds to a yield stress behavior in the fluid that tends to create a barrier against the flow. Rheological studies reveal with an increment of hydrophilic silica aerogel concentration up to 1 phr, the storage and loss modulus increases against pure specimen. Also, the increase of first normal stress indicates the formation of physical solid network-like and changing behavior to solid-like. According to relaxation time spectrum of PP/PET polymer blend, silica aerogel in 1 phr concentration has the highest influence in the reduction of droplets of the dispersed phase and increasing interphase thickness between two phases. 'K' and 'n' parameters in the power-law model showed the shear thinning and pseudo-plastic properties of the polymer blend. The results obtained from using rheological FZM model indicate the conformity of model on experimental data for experimental data in concentration up 1 phr of hydrophilic silica aerogel
