Preparation and characterization of spherical PP/PB alloys with MgCl2-supported Ziegler-Natta catalyst

Polypropylene (PP)/polybutene-1 (PB) alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene (iPP) particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles. Finally, iPP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly(buteneco-propylene) random copolymers and poly(butene-block-propylene) block copolymers. SEM measurements verified that the PB phases with size in the range of 300–400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.