Mechanical Modulus Metallocenes

Cycloolefin copolymer (COC) is an amorphous, clear metallocene product of norbomene and ethylene with a spectrum of attractive performance characteristics. Thus, COC (MFI at 190 °C and 2.16 kg = 1.7 dg min, p = 1,020 kg m ) was blended with C2+6 LLDPE (MFI at 190 °C and 2.16 kg = 3.2 dg min , p = 920 kg m ). The mechanical properties of the blends indicate immiscibility, despite the increased LLDPE crystallinity. The presence of COC improved the thermo-oxidative stability. Quasi-static tensile tests showed that increasing fraction of COC in the blends accounts for an enhancement of the elastic modulus and a decrease in the strain at break, while tensile strength passes through a minimum. A significant reduction of the creep compliance of LLDPE could be achieved only for the COC fractions exceeding 20 wt% (Dorigato et al. 2010). 

The melting temperature, extent of crystallinity, modulus, and mechanical behavior depend on the method of manufacture and the addition of comonomers, as well as overall molecular weight. Polyethylene is manufactured by several major processes (1,2) The high-pressure, free-radical polymerization, the Ziegler process, and the newer metallocene-catalyzed polymers and the metallocene-Ziegler processes see Table 14.2. 

---