The Role of Oxygen and Peroxide Initiators in High-Pressure Polyethylene Production
Irada Garayeva 1* , Mushkunaz Nazarova 1 , Samir Salimli1 ,
Arzu Isagzade1 , and Zumrud Yusifova1
Abstract. In this study, the effect of oxygen and initiator systems on LDPE properties under high-pressure conditions was investigated. Oxygen reduces molecular weight (MW) and increases chain branching, leading to reduced thermal stability; however, at optimal concentrations, it can contribute to the formation of a more stable polymer structure under controlled conditions. Peroxide systems improve control of molecular weight distribution (MWD) and increase mechanical strength by 15–20%. Di-tert-butyl peroxide (DTBP) regulates melt flow index (MFI) and molecular weight (MW) of the polymer by generating active radicals as a result of thermal decomposition and helps maintain product stability. Compared to oxygen-based systems, peroxide-based initiation increases mechanical strength by approximately 15–20% and elongation by 10–15%, while providing improved control of molecular weight distribution. In addition, peroxy-radical reactions occurring in the presence of oxygen can affect the composition of the radical pool in the system and change the course of the initiation phase under certain process conditions. However, such reactions also increase the likelihood of the formation of hydroperoxide and carbonyl-type oxidation products, which negatively affect quality parameters such as polymer stability, color indicators, and odor. The results of the conducted studies show that the type of initiator used and its concentration are among the main factors determining the physical and mechanical properties of the synthesized polymer. These findings provide practical guidance for optimizing initiator selection and dosage in high-pressure polyethylene production.
Keywords: polyethylene, initiator, polymerization, oxygen, di-tert-butyl peroxide (DTBP)