Báo Cáo Mechanism and kinetics of chain transfer and back-biting reactions in polyethylene addition

ABSTRACT
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The paper introduces new a researching method to study the mechanism and kinetics of the reactions in the polymerisation of ethylene by computer with the aids of GAUSSIAN 98 softwares. Calculation using density functional theory with the popular B3LYP at the 6-31g(d) was suitable for the research. Free radical ethyl and ethylene were good enough for modelling the propagation in the addition of polyethylene. The rate of propagation depending on temperature was an exponent function with the activative energy of 28 kJ/mole. The termination by chain tranfer using propanal was mainly the abstraction of hydrogen of carbonyl group. The calculated percentage of product was around 85 % at 220[SUP]o[/SUP]C that was in good agreement with the experimental results. At 300[SUP]o[/SUP]C, the efficient of termination by chain transfer of propanal was 90, 5% in comparison to 1,8 % of propane, 34,9 % of propene and 49, 4% of butene-1. The mechanism and kinetics of back-bitting of polyethylene radical were investigated. The branches of butyl and pentyl were obtained with the distribution of 4-5 branches per 1000 C of polyethylene at 300[SUP]o[/SUP]C.