Metallocene catalyzed polyethylene

M. Ohgizawa, M. Takahashi and N. Kashiwa, Metallocene catalyzed polyethylene with unique rheological property , MetCon 95 Proceedings, USA, May 1995. 

Fig. 8 Loss angle as a function of frequency at 150°C obtained for high-density, metallocene catalyzed polyethylene samples of increasing long-chain branching. (From Ref.. )...

The double reptation model was used to evaluate viscoelastic behavior of metallocene-catalyzed polyethylene and low-density polyethylene blends by Peon et al. (2003). They compared their results with those obtained for HDPE/BPE blends prepared under similar conditions. Since this model assumes miscibility between the mixed species, the experimental viscosity of HDPE/BPE blends showed only small deviation compared to that expected according to the reputation miscible model. However, the model underestimated the compositional dependence of the zero-shear viscosity for mPE/LDPE blends, especially at intermediate levels. The enhanced zero-shear viscosity in immiscible blends such as PETG/EVA, PP/EVA, or EVA/PE blends was found to be more abrupt than it is for mPE/LDPE blends (Lacroix et al. 1996, 1997 Peon et al. 2003). 

R-C. Chiu, S.-M. Lai, K.-T. Ti, Characterization and comparison of metallocene-catalyzed polyethylene/thennoplastic starch blends and nanocomposites, Polymer Testing 28 (3) (2009) 243-250. 

Fig. 23. Melt viscosity data for LDPE, LLDPE, and mLLDPE all normalized tol g/10 min melt index. Also shown is new type of easy-processing metallocene-catalyzed polyethylene, mPE. To convert Pa-s to P, multiply by 10.

Equistar, ExxonMobil, Huntsman, Montell, Phillips, Union Carbide, and West-lake. Commercial mLLDPE is available from Dow, ExxonMobil, and Phillips. Globally, it is estimated that there are eleven commercial suppliers of metallocene-catalyzed polyethylene (102). 

LDPE is still the preferred resin for extrusion coating. Because of the narrow molecular weight distribution of LLDPE (and also of metallocene-catalyzed polyethylenes), the resins are more difficult to extrude and have greater neck-in than LDPE. 

Fig. 11 Dependence of the steady-state tensile viscosity riE on the tensile stress at 150°C for three metallocene-catalyzed polyethylenes differing in branching topology. Curves are fitted to the data points to guide the eye. Reprinted from [120], with kind permission from American Chemical Society.

Dr. Sehanobish has authored a series of publications and holds more than 25 patents in the areas of polyethylene pipes, blown and cast films, speciality fibers and films, and TPOs. His research is the basis for the INSITETM technology platform and new resin families such as ENGAGE , AERNITY , NORDEL ip and ELHE . The INSITE technology received the R D 100 Award in 1994 from R D Magazine, and the ELITE enhanced polyethylenes received the R D 100 Award in 1999. These efforts also resulted in currently more than one billion pounds per year of sales of metallocene-catalyzed polyethylene resins by The Dow Chemical Company. 

There are two methods used to blend polypropylene and EPDM rubber to make a TPO. The original method, still used extensively, is to simply mechanically blend the two polymers together with high shear mixing at an elevated temperature. However, a newer procedure employs new catalyst technology to blend EPDM and PP in the polymer reactor itself. This newer technique lowers the TPO production costs however, this type of TPO can only be obtained from the polymer manufacturers themselves. Reactor-produced TPOs can also be made softer than the mechanically blended TPO types. Some TPOs are also based on polyethylene as well (such as metallocene-catalyzed polyethylene), see Figure 6.7. 

Costeux, S., and Wood-Adams, P., Beigzadeh, D. Molecular structure of metallocene-catalyzed polyethylene RheologicaUy relevant representations of branching architecture in single catalyst and blended systems. Macromolecules (2002) 35, pp. 2514-2528... 

Malmberg, A., Gabriel, C., Steffi, T., Munstedt, H., Lofgren, B. Long-chain branching in metallocene-catalyzed polyethylenes investigated by low oscillatory shear and uniaxial rheometry. MacromoL (2002) 35, pp. 1038-1048. 

The effect of the peroxide on the molecular weight distribution was ignored in these calculations. In (b),the polymers are an LLDPE (data circles, theory solid line M, = 13.8 10 M /M = 4.2, with LCBI = 0.13), and a metallocene-catalyzed polyethylene (data triangles, theory dashed line /W =8.5 10 ,/W /M =2.4,with LCBI =0.51) Data of Shroff and Mavridis... 

Vega, J. E, Fernindez, M., Santamaria, A., Munoz-Escalona, Lafuente, P. Rheological criteria to characterize metallocene catalyzed polyethylenes. Macromol. Chem. Phys. (1999) 200, pp. 2257-2268... 

Doerpinghaus, R J., Baird, D. G. Assessing the branching architechtnre of sparsely branched metallocene-catalyzed polyethylenes nsing the pompom constitntive model. Macromolecules (2002) 35, pp. 10087-10095... 

Sulfate on Rheological Behavior and Meehanieal Properties of Metallocene Catalyzed Polyethylenes Used in Medical Devices , SPE ANTEC Technical Paper, (2004), Vol.50,... 

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