The effect of polypropylene-graft-maleic anhydride on the morphology and dynamic mechanical properties of polypropylene/polystyrene blends

摘要

Polypropylene (PP) and polystyrene (PS) blends were prepared by melt processing in a haake at 180 degrees C. PP/PS blends are immiscible and the blend morphologies were characterized by scanning electron microscopy. The viscoelastic properties were characterized using dynamic mechanical analysis (DMA) with reference to blend ratio. The blend morphologies such as matrix droplet and phase inverted morphologies were observed. The storage modulus of the blends increased with increase in PS content and the value was maximum for neat PS. DMA showed changes in the polystyrene glass transition temperatures (T-g) over the entire composition range. There was a sharp increase in the T-g of PS with increasing PP content in the blend and a 12 degrees C elevation in T-g was observed. The increase in T-g was explained by proposing a new model based on the physical interaction between the blend components. It is assumed that the different effects by the PP phase resulted in the formation of constrained PS chains leading to high T-g values. The addition of PP-g-MAH has a positive effect on the morphology, increases the storage modulus, and decreases the T-g till 80/20 blends. However, for PP/PS blends with higher concentrations of PS, the PP-g-MAH has little effect or adverse effect on the morphology, and storage modulus, but decreases the T-g.