Synthesis of Ethylene-Propylene-Diene Terpolymers and Their Heterophase Compositions with Polypropylene in the Presence
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ICAL PHYSICS OF POLYMERIC MATERIALS
Synthesis of Ethylene-Propylene-Diene Terpolymers and Their Heterophase Compositions with Polypropylene in the Presence of Metallocene Catalytic Systems A. M. Aladysheva, A. N. Klyamkinaa, P. M. Nedorezovaa, *, and E. V. Kiselevaa a
Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received May 14, 2019; revised May 14, 2019; accepted June 20, 2019
Abstract—Ethylene-propylene-5-ethylidene-2-norbornene terpolymerization is studied in a liquid propylene medium using catalysts based on metallocenes (MCs) of C2- and C5-symmetry, differing in the nature of bridges and ligands and activated by MAO. It is shown that the investigated MCs of C2-symmetry do not ensure the synthesis of terpolymers combining a high molecular weight (MW) and good diene incorporation. In the presence of a MC of Cs-symmetry Ph2C(CpFlu)ZrCl2, terpolymers with an MW of 120000 to 160000 and a diene content of 2.0 to 5.3 wt % are obtained with a high level of activity. New heterophase compositions based on isotactic PP and ethylene-propylene-diene terpolymers, which have a good balance between strength and elasticity, are synthesized. Keywords: terpolymerization, metallocene catalysts, propylene, ethylene,5-ethylidene-2-norbornene, liquid propylene, heterophase compositions, physical-mechanical properties DOI: 10.1134/S1990793120040028
INTRODUCTION The copolymerization of propylene with large amounts of ethylene or their terpolymerization with dienes leads to the production of amorphous rubber-like materials—a fast-growing class of elastomers [1, 2]. Materials based on triple ethylene-propylene-diene rubber (EPDM) are widely used in the automotive, medical, construction, cable, and other industries due to their strong resistance to oxidative, ozone, and heat aging, as well as their good physical and mechanical properties. As the demand for these materials is constantly increasing, special attention is paid to the search for effective catalysts for the synthesis of EPDM. For the synthesis of EPDM, both conventional Ziegler–Natta catalysts are used, mainly based on vanadium compounds and less often titanium, as well as homogeneous metallocene (MC) catalysts [3, 4]. However, vanadium catalysts are characterized by the low yield of the final product and wide molecular mass distribution (MMD) due to the presence of various active centers limiting the application of the materials obtained with their use. When EPDM titanium catalysts are used in the synthesis, composite-nonuniform block sequences of ethylene and propylene are formed, which contribute to the undesirable crystallinity of the polymers [5]. At present, MCs are among the most promising catalysts used to prepare new polymer materials based on polyolefins [6–8]. Homo-
geneous MC systems allow us not only to regulate the microstructure of polymer chains but also to obtain polymers homogeneous in composition with the required molecular mass characteristics [9]. In the synthesis of ol
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