Preparation and characterization of PP and PP-g-(MAH-co-St)/hyperbranched poly(amide-ester) blends

Free-radical melt grafting of the multi-monomer system of maleic anhydride (MAH)/styrene (St) onto polypropylene (PP) was carried out using a single-screw extruder in the first step. Then melt mixing method was employed to prepare two types of blends, polypropylene(PP)/hyperbranched poly(amide-ester)(HBP) and maleic anhydride grafted polypropylene [PP-g-(MAH-co-St)]/HBP blends. The processability and compatibility of the two blends were investigated as a function of HBP added. Through processing and rheological studies, the results showed that HBP was an effective processing additive. The melt viscosity of the PP/HBP blends dropped in proportion to the amounts of HBP added, and melt viscosity of the PP-g(MAH-co-St)/HBP blends decreased by the addition of up to 7 %wt HBP, after which the blend viscosity remained essentially constant. Characterization including scanning electron microscopy (SEM), differential scanning calorimetry (DSC,) and Fourier transform infrared spectroscopy (FTIR) data indicated that the HBP formed immiscible blends with PP. A significant degree of compatibilization occurred in the systems of [PP-g-(MAH-co-St)]/HBP, which is evident by shifts in the thermal transitions of the HBP phase and by morphology refinement observed by scanning electron microscopy.