Synthesis of spherical polyethylene/poly(1-butene) reactor blends with two-stage sequence polymerization technology

In this paper, a series of polyethylene (PE)/poly(1-butene) (PB) reactor blends (PE/PB reactor blends) with excellent spherical particle morphology were firstly prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. The polyethylene particles formed in the first stage ethylene polymerization can be used as micro-reactors to initiate the bulk polymerization of 1-butene. The spherical reactor blends as novel thermoplastic polymers were obtained within reactor. The composition of the reactor blends was studied by solvent fractionation. The particle morphology, chain structures, physical and mechanical properties of the reactor blends and their fractions were further characterized by scanning electron microscopy (SEM), gel permeation chromatography (GPC), 13-carbon nuclear magnetic resonance (13C NMR), differential scanning calorimeter (DSC) and tensile tester. The reactor blends are mainly composed of high density polyethylene (HDPE, fraction C), stereoblock isotactic poly(1-butene) (iPB) and a small amount of poly(ethylene-b-1-butene) block copolymers (fraction B), moderate isotactic poly(1-butene) and poly(ethylene-co-1-butene) random copolymers (fraction A). The HDPE incorporation in the first stage not only resolves the reaction engineering problems, but also contributes to the higher isotactic stereoregularity of 1-butene polymerization. The reactor blends present higher tensile strength and lower permanent deformation with the incorporation of PE component.