Abstract
In this work, homopolymerization of propylene for synthesis of different molecular weights polypropylene was done using an isospecific metallocene catalyst by changing the polymerization conditions such as Al/Zr (Aluminium/Zirconium) ratio, temperature, pressure and polymerization time. The effects of the polymerization conditions on the molecular weight and other polymer properties have been discussed according to the results obtained. The results indicate that the activity of polymerization increased with increasing the Al/Zr mole ratio and reached a maximum value at a ratio of 2000. In relation to the mole ratio, the molecular weight also followed the same trend. The activity was also seen to increase with increase in temperature. The molecular weight increased with increasing the polymerization time at both 0°C and 25°C, but reduced with increase in time at 40°C. The increase of pressure also increased activity but lowered the molecular weight, indicating β-H elimination to the monomer.
Highlights
Polypropylene is an important plastic and is used in many different forms and applications through a range of manufacturing processes
The results indicate that the activity of polymerization increased with increasing the Al/Zr mole ratio and reached a maximum value at a ratio of 2000
When the concentration of Al/Zr was increased, the molecular weight increased until a Al/Zr mole ratio of 3000 had been reached
Summary
Polypropylene is an important plastic and is used in many different forms and applications through a range of manufacturing processes. Blow moulded containers, such as bottles for foods, shampoos and other liquids, form part of everyday experience. One of the main advantages of homogeneous polymerization catalysts compared to multisited heterogeneous catalysts is their well defined active sites, which allows us to synthesize polymers with specific microstructures and more narrow molecular weight distributions which are quite uniform. The aim of this work was the synthesis of various molecular weight polypropylenes including high molecular weight polypropylene. This was achieved by varying the polymerization conditions such as temperature, pressure, Al/Zr ratio and polymerization time. The structure of the catalyst used was as shown below
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