Iran Polymer and Petrochemical Institute Polyolefins Journal 2322-2212 11 1 2024 02 01 Ultra-high molecular weight polyethylene synthesis using externally modified Si-Mg-Ti based Z-N catalyst system 61 70 2008 10.22063/poj.2023.3483.1279 EN Hiren Bhajiwala Reliance Research Development Group, Reliance Industries Ltd., Reliance Corporate Park, Ghansoli, Navi Mumbai, Maharashtra – 400701, India Virendrakumar Gupta Reliance Research Development Group, Reliance Industries Ltd., Reliance Corporate Park, Ghansoli, Navi Mumbai, Maharashtra – 400701, India Journal Article 2023 08 26 Ultra-high molecular weight polyethylene (UHMWPE) was synthesized using Bi-supported SiO<sub>2</sub>/MgCl<sub>2</sub>/TiCl<sub>4</sub> (Si-Mg-Ti) Ziegler-Natta catalyst in conjugation with triethyl aluminum (TEA). The impact of temperature and the presence of a chain-terminating agent were examined in the context of ethylene polymerization. The findings showed that as temperature decreases, the activity of the polymerization decreases, and the molecular weight of the polymer increases. Conversely, in the presence of a chain-terminating agent, the molecular weight of the polymer decreases. The introduction of Triethyl borate (TEB) and Tetraethoxy silane (TEOS) as an external donor has a pronounced effect on the catalyst activity, causing a significant decrease, while simultaneously leading to a substantial increase in the viscosity average molecular weight (M<sub>v</sub>). Additionally, when a chain-terminating agent is added along with Triethyl borate (TEB) in the system, it results in a significant decrease in molecular weight, albeit with a slight increase in activity compared to a system without a donor. The crystallinity, particle size and bulk density of the polymer synthesized with and without external donor also investigated. Si-Mg-Ti Ziegler-Natta Catalyst UHMWPE Ethylene polymerization External donor http://poj.ippi.ac.ir/article_2008_6ae141894c952ebe2facfd40d5982b0b.pdf