Mathematical modelling and control of chemical composition distribution ofethylene/alpha-olefin copolymers made with single and combined metallocenecatalysts

The single-site nature of metallocene catalysts permits the production of p olyolefins with narrow distributions of molecular weight, chemical composit ion and comonomer sequence length. This enhanced control over polymer chain microstructure permits, in principle, the synthesis of polyolefins with we ll-controlled properties. In order to benefit from this enhanced control, o ne needs to understand how polymerization conditions and catalyst type affe ct polymer microstructure, as well as how the existing characterization tec hniques can be used to determine their microstructure. This manuscript inve stigates the effect of polymerization conditions and catalyst type on the c hemical composition distribution (CCD) of ethylene/alpha-olefin copolymers made with single-site and Ziegler-Natta catalysts. Mathematical models will be used to describe CCD of polyolefins made on single- and multiple-site-t ype catalysts. Crystallization analysis fractionation (CRYSTAF) and tempera ture rising elution fractionation (TREF) are used to measure the CCD of the se resins. It will be shown that the interpretation of CCDs with these math ematical models can be used to enhance our understanding on the nature of a ctive sites present in metallocene and Ziegler-Natta catalysts.