Preparation of Ultra High Molecular Weight Polyethylene with MgCl2/TiCl4 Catalysts: Effect of Temperature and Pressure

摘要

The polymerization of ethylene (E) was carried out using a MgCl2-supported TiCl4, catalyst in conjunction with triethylaluminium as a cocatalyst The effects of the polymerization temperature (T_p) and E pressure (P_E) on E polymerization were studied. The maximum catalyst activity was obtained at 40 °C. The melting temperature (T_m ) and crystallinity (X_c) were less affected by the T_p. The molecular weight decreased with increasing T but the poly-dispersity index (PDI) increased. In addition, the effect of two stepwise T_p on E polymerization was investigated and the bimodal gel permeation chromatography (GPC) curve was obtained. The catalyst activity increased drastically with increasing P_E. The higher P_E in the range of 1 -12 kgf/cm~2 showed a higher M_v of the ultra high molecular weight polyethylene (UHMWP_E) obtained, whereas increasing P_E decreased the PDI. Because it was very difficult to obtain the molecular weight distribution of UHMWP_E through GPC analysis, the molecular weight distribution was analyzed from rheometry measurements of the UHMWP_E melt.