Ethylene polymerization was performed with $MgCl_2/THF/TiCl_4$ catalyst combined with $AlEt_3$ in the range of temperatures between 50 and 80℃ and in the range of ethylene pressures between 2 and 4 Kg/㎠. The effect of hydrogen and $AlEt_3$ on the molecular weight of polyethylene was also observed. The polymer samples was taken from the reactor at the polymerization time of 5, 10, 15, 20, 30, and 60 minutes without the obstruction of the polymerization. Molecular weight increased as the ethylene pressure increased, as the temperature decreased and as the concentration of $AlEt_3$ and hydrogen decreased.
The morphology of the polymers taken at the same periods during the polymerization was investigated. A globular texture was observed regardless of the presence of hydrogen. Until the polymerization time of 15 minutes, the growth of globules was more rapid in the presence of hydrogen than in the absence of hydrogen. The average particle size of globules became larger in the absence of hydrogen after 15 minutes of polymerization than that of globules in the presence of hydrogen.
A computer simulation on the molecular weight was carried out based on such chain transfer rate constants as Ktr,Al,Ktr,M, and Ktr,H. In addition to these parameters, ki was also varied to study the effect of these parameters on the molecular weight. It was shown that the molecular weight of polymer were dependent on the initiation rate constant (ki) until 10 minutes of polymerization. After 10 minutes of polymerization, the variation of the molecular weight was negligible without regard to the change in ki.
Using the various comonomers (propylene, 1-butene, 1-hexene and 1-dodecene) copolymerization of ethylene was performed. The physical properties such as density, crystallinity and molecular weight varied with the concentration of participating comonomer. Copolymerization was performed with $MgCl_2/THF/TiCl_4$ catalyst at 80℃. Density of the copolymer became decreased to 0.915 g/㎤ at $[C_4H_8]/[C_2H_4]=0.5$. Molecular weight of the copolymer sharply decreased as the concentration of comonomers increased.
