Morphology, Structure And Properties Of Polypropylene Alloy By In-reactor Blending

The crystallization morphology and dynamic rheology characteristics of polypropylene alloys prepared by in-reactor blending technique (catalloy) have been studied by the methods of polarized microscopy (PM), scanning electron microscope (SEM), differential scanning calorimetry(DSC) and advanced rheometric expansion system(ARES) in the paper. Some related data involving in morphology, structure and specification of the catalloy have been believed to be helpful to molecular design and synthesis for polypropylene catalloy.Through observating the morphology of annealed catalloy samples by using PM, homo-polypropylene (PP), common block polypropylene copolymer, PP/polyethylene (PE) and PP/ethylene propylene diene monomer(EPDM) blends, we found that the spherulite numbers of the catalloy is much more than those of PP in common use. On the other hand, the spherulites are well distributed, which results in higher impact strength of the catalloy polypropylene.Through SEM observation, we found that the brittle surface of the catalloy samples appears more coarser than blends, but more smoother than that of PP copolymer.The melting behavior of all samples investigated here has been characterized by using DSC analysis. The results revealed that the catalloy SI exhibits only one melting peak during melting process and has much lower melt temperature, indicating that propylene and ethylene segments in chain structure of catalloy are compatible and their interaction is attributed to bonding. Moreover, DSC analysis of polypropylene catalloy prepared under different synthetic conditions declared that only one melting peak appears for all samples which contain different ethylene content. These also give a clue to good compatibility between propylene and ethylene segments in catalloy. The melt peak of polyethylene occurs when ethylene content approaches 18.1%.The dynamic rheological measurements have been conducted by using ARES. The results exhibited that S I shows a dynamic viscosity( n' ) ~-frequency( w) curvesIIsimilar to general block copolymers. The catalloys show lower loss tangent(tan 6) values than those of other system within frequency region, especially in low frequencies. The results also showed that catalloy samples exhibit a pronounced elasticity within wide frequencies, according to the analysis of dynamic storage modulus G' and loss modulus G...