INFLUENCE OF SHEARING ON IMPACT POLYPROPYLENE COPOLYMER: PHASE MORPHOLOGY, THERMAL AND RHEOLOGICAL BEHAVIOR

The influences of shearing conducted by a Brabender rheometer on phase morphology, thermal and rheological behavior of a commercial impact polypropylene copolymer (IPC) were studied. The crystallization and melting traces show that short-time annealing at 210℃ is unable to completely erase the influence of shearing on the samples. When the samples which were treated at a rotation speed of 80 r/min crystallize at a cooling rate of 10 K/min, their Tcs and corresponding Tms obviously rise with the increase of shearing time. Furthermore, the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time. The rheological measurement results show that the treated samples exhibit different G~ dependences. The second plateau appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min, and linear G~ dependence is observed at other rotation speeds. In addition, it is found that the appearance of the second plateau depends on the shearing time when the rotation speed is fixed. According to SEM observations, it is proposed that the second plateau of IPC samples should be ascribed to the aggregation of dispersion particles.