High MeltStrength Polypropylene with Wide MolecularWeight Distribution Used as Basic Resin for Expanded PolypropyleneBeads.

The high melt strength polypropylene(HMSPP) is fabricated by directpolymerization through controlling the species and ratios of the externalelectron donors in the Ziegler–Natta catalyst system at differentreaction stages. The polypropylene exhibits wide molecular weightdistribution and higher melt strength. The expanded polypropylene(EPP) beads are prepared by the above HMSPP through an autoclave-basedbatch process. The effects of melt strength on the cellular morphologyof EPP are investigated by scanning electron microscope and melt strengthmeter, respectively. Results indicate higher melt strength facilitatesthe control of the foaming process and the cellular structure comparedwith a commercial propylene homopolymer such as T03. The bimodal cellstructure is obtained with the single foaming agent CO2in both of the EPP beads from HMSPP and commercial polypropylene. [ABSTRACT FROM AUTHOR]