Review Of Shear Induced Crystallization Of Isotactic Polypropylene Based Materials

The mechanism and morphology of shear induced crystallization of isotactic polypropylene (iPP) in its blends or composites were analyzed, compared and discussed in this work. For pure iPP, crystalline structure of cylindrites can be observed easily under very low shear rate. But for iPP/poly (ethylene-co-octene) (PEOc) blends, cylindrites were observed after shear in the very late stage of phase. separation only when the shear rate was large enough. The morphologies of cylindrites were multi-formed and different from the pure iPP because PEOc is an elastermer and the PP/PEOc blend system is phase separated. For PP/OMMT (organo-montmorillonite, clay) composites the fillers could form mesoscale network in the polymer matrix. The effect of shear on the heterogeneous nucleation, cylindrites formation and-morphology of spherulites were discussed and compared with pure iPP and PP/PEOc blend. The clay content is also a very important parameter in the crystallization behavior. For all three systems the mechanism of shear induced cylindrites was initiated by the structure of the entangled polymer chain network which formed bunddled core nuclei.