All-polyethylene compositions of ultrahigh molecular weight polyethylene (UHMWPE) synthesized in one-step ethylene polymerization with combinations of zirconocene and iron-based catalysts

Reactor polymer compositions (RPC) based on ultrahigh molecular weight polyethylene (UHMWPE) and low molecular weight HDPE (LMWPE) were obtained by a single-stage polymerization of ethylene over a mixture of metallocene and post-metallocene catalysts. The combinations of precatalysts rac -(CH 3 ) 2 Si(Ind) 2 ZrCl 2 (Zr) and 2,6-[2,4,6-((CH 3 ) 3 C 6 H 2 NCCH 3 ) 2 C 5 H 3 N]FeCl 2 (Fe) activated by methylaluminoxane (MAO) were used. It was shown that ethylene polymerization at 30 °C with Zr/MAO leads to the production of UHMWPE with Mw = 1000 kg mol −1 and narrow MWD (3.1). Linear LMWPE with Mw = 48 kg mol −1 and wide MWD (18) was formed in the presence of Fe/MAO. Compositions of UHMWPE/LMWPE with calculated content of the LMWPE fraction from 6.3 to 29 wt% were synthesized over (Zr + Fe)/MAO catalyst. Proportion of Fe in (Zr + Fe) was varied from 0.17 to 0.55. The comparison of the shape and size of the UHMWPE, LMWPE and UHMWPE/LMWPE nascent particles was carried out using the scanning electron microscopy (SEM) technique. It was shown by the DSC method that the introduction of LMWPE into UHMWPE led to the increase of RPC crystallinity with a deviation from the additivity rule. The synthesized RPC have good tensile and dynamic mechanical properties. The increase in the proportion of LMWPE in the RPC caused a sharp increase in its tensile modulus ( E ) and dynamic mechanical modulus ( E′ ). These characteristics of RPC containing 29 wt% of low molecular weight fraction were close to the values of E and E′ of pure LMWPE. Graphical abstract