Polyethylene Structure Attained with a Single-Site Catalyst

2 Polyethylene Structure Attained with a Single-Site Catalyst 

Single-site catalysts primarily produce only one type of polymer structure, which is based on the polymerization characteristics of any particular type of catalyst. The polyethylene has a relatively very narrow molecular weight distribution with a polydispersity of 2.0 (defined as one Flory distribution with an value of 2.0 due to one type of active center involving a 

The xmiform branching distribution found in this new type of polyethylene, and the relatively high reactivity of these catalysts with higher 1 -olefins, has allowed the manufacture of ethylene/1-olefin copolymers containing very high levels of comonomer such as 1-butene and 1-hexene, i.e., 5-20 mol% comonomer. Consequently, the density range of the polyethylene 

Single-site ethylene polymerization catalysts based on titanium or zirconium as the active center are primarily used in the low-pressure manufacture of polyethylene with a relatively very narrow molecular weight distribution to include high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE) and very low density LLDPE to include amorphous material. Table 4.1 summarizes a few examples of end-use applications for this type of polyethylene in terms of the density, molecular weight distribution and molecular weight for various applications. Note that in Table 4.1 a Melt Flow Ratio (MFR) value of 16 approximately corresponds to an polydispersity value of 2.0, which is indicative of a 

Product Type Melt Index (MI) a,/ Flow Index MFR (FI/MI) Density ( cc) 

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