Polydispersily index

These metallocene/aluminoxane catalysts are considered "single site" catalysts and therefore produce PE with veiy narrow polydispersily index (close to Stockmayer s distribution where the polydispeisity index is 2) and narrow chemical composition distribution, CCD. They ate usefiil in producing HDPE, and LLDPE. However, one drawback to the metallocene/aluminoxane catalysts is that significant quantities of aluminoxane by-products must be removed after production, due to the high Al/Zr ratios required for optimum performance. The primary role of the aluminoxane is in formation of the active site species. (The initial stracture in the catalytic cycle shown in Figure 5.) The series of complexation and fast alkylation... 

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