Single-site catalysts are commercially used for the production of polyethylene (PE) and polypropylene (PP). These polymers are ubiquitous throughout our society and their use and material properties have greatly increased since their initial discovery. In order to process these polymers into useful products, the polymer is frequently brought into the melt state and exposed to a variety of shear conditions prior to forming the final product. The ease of forming these products is governed in part by the polymer’s rheology (e.g. extrudability and bubble stability for film blowing applications). Polymer rheology is directly impacted by the following factors: (i) molecular weight distribution, (ii) comonomer composition and (iii) long chain branching.<br/><br/>This presentation will summarize an approach that can be taken to choose a catalyst(s) and reactor conditions to achieve a desired polymer rheology. The approach relies on the combination of kinetic and rheological modeling to identify the rate constant ratios needed for the catalyst(s) and the corresponding conversions required within the reactor. These choices permit tailored rheological properties by directly controlling the molecular weight distribution and long chain branching within the polymer. This work is a combination of both experimental and computational efforts and has been applied to polyethylene and polypropylene.

Identifying catalysts and reactor conditions for tailored polymer rheology

2019 Fall National Meeting

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