In this paper

the kinetics of the coordination polymerization of ethylene have been studied at normal pressure with the highly active catalyst system TiCl4/MgCl2/Al(C2H5)3 (Ⅰ) in comparison with the highly active catalyst system TiCl4/MgCl2/Al(C2H5)3/Zn (C2H5)3 (Ⅱ). The specific number of active centers [C] and the propagation rate constants (kp) were determined by kinetics method for the ethylene polymerization. The value of [C] for the ethylene polymerization with system (Ⅰ) was found to be 0.02 to 0.06 mole/mole Ti in the range of poly-merization temperature 25 to 45℃

and the apparent activation energy to be 2.45 kcal/mole. The kinetics behavious of the system (II) was similar to the syste m(I)

but the value of [C*] of the system (II) was much greater than that of system (I)

which leads to that the catalytic efficiency increases greatly in comparison with that of the system (I). The chain transfer constants were also determined. Zine diethyl is more effective chain transfer agent that causes the great decrease in the molecular weight of polyethylene.