Development of Bimodality Criterion for the Sequence Length Distribution of Ethylene/1-Olefin Copolymers

Combination of two single-site-type metallocene catalysts can be used to produce polymers with well-defined, broad microstructural distributions. Copolymers with unimodal and bimodal microstructural distributions were known to have distinct properties; therefore, it would be useful for the product development to have bimodality criterion for these microstructural distributions. In this work, a bimodality criterion for ethylene sequence length distribution (SLD) of ethylene/1-olefin copolymers produced with two metallocene catalysts was theoretically developed to predict if a given combination of two metallocene catalysts would produce copolymers with bimodal or unimodal SLD. The proposed criterion was validated using simulation data of four hypothetical ethylene/1-olefin copolymer blends, each with various compositional ratios. The characteristics of simulated SLD results were in a good agreement with the predictions from the proposed criterion.