Unusual tuning of mechanical properties of isotactic polypropylene using counteraction of shear flow and β-nucleating agent on β-form nucleation

A study was conducted to tune the mechanical properties of isostatic polypropylene (iPP) using counteraction of shear flow and β-nucleating agent on β-form nucleation. The β-nucleating agent (TMB-5) was first melt mixed with iPP in a twin-screw extruder to form a 1.0 wt % β-nucleating agent masterbatch. The masterbatch was melt compounded with fresh iPP to produce iPP pellets with 0.2 wt % of TMB-5. The screw speed was fixed at 82 rpm and the processing temperature profile was 170-180 °C from hopper to die. The iPP pellets were injection-molded into dumbbell bars in an injection temperature profile of 170-200 °C from hopper to nozzle. The conventional injection molding (CIM) was also carried out under the same processing conditions for comparisons. It was observed that the oscillation shear injection molding (OSIM) β-iPP samples exhibited better mechanical properties when compared with CIM iPP samples.