A Method for Synthesis a High Density Polyethylene by Coordination Polymerization

A method is described to achieve appropriate mechanical properties and flowability of high density polyethylene through tandem ethylene polymerization with a coordination multisite catalyst. In the first step of polymerization, low molecular weight homopolymer of ethylene in the presence of hydrogen and in the next step, high molecular weight copolymer of ethylene with 1-butene in the absence of hydrogen were produced. Increasing hydrogen amount leads to increase of polydispersity index. Depending on the polymerization times, increasing hydrogen concentration can either increase or decrease average molecular weights. The effects of the mentioned parameters on the processability and mechanical properties of some samples were discussed.

Keywords:

polyethylene , polymerization , Ziegler-Natta , mechanical properties , molecular weight