The effect of polypropylene/polyamide 66 blending modification on melt strength and rheologic behaviors of polypropylene

Common linear polypropylene (PP) was modified by blending with polyamide 66 (PA66) under the act of compatibilizer in a twin-screw extruder in an attempt to improve the melt strength (MS) of PP. The MS of pure PP and modified PPs were measured by MS testing unit at three temperature of 190, 210, and 230 °C, and the MS improvement of PP was verified. The MS of the modified PPs increased with increasing the content of PA66. The steady- and dynamic-shear rheological behaviors of pure PP and modified PPs were investigated using a capillary rheometer and a parallel-plate rotating rheometer. The steady-shear rheological analysis results revealed that modified PPs had higher melt shear viscosity, stronger non-Newtonian behaviors, and higher zero shear-rate viscosity. The dynamic-shear rheological analysis showed modified PPs had higher melt complex modulus and smaller phase angle, which indicated that the melt viscosity and melt elasticity of PP were also enhanced. The modified PPs was characterized by DSC. DSC results revealed that the PA66 phase and PP phase of the modified PPs were in state of crystallization. The enhancement of MS, melt viscosity, and melt elasticity of modified PPs could be due to undisaggregated PA66 crystallization phase within the melt of PP blends.