Polypropylene Zero-shear viscosity

In addition to zero-shear viscosity, material elasticity plays an important role in determining coalescence behavior in the rotational molding process.For rotational molding grade material, this effect was first recognized from the experimental results obtained with impact modified polypropylenes and is illustrated in Fig. In this work, the relative elasticity of resins... 

Figure 7.27. Concentration dependence of zero shear viscosity of polypropylene blends with two linear low density polyethylenes at 190°C. Points are experimental with error bars indicating the standard deviation [Dumoulin, 1988]. Lines are computed from Eq 7.125.

FIGURE 3.6 Zero shear viscosity as a function of weight-average molecular weight and viscosity-average molecular weight for polypropylene. (From Minoshima, W. White, J.L. Spruiell, J.E. Polym. Eng. Sci., 1980, 20, 1166, With permission.)... 

Hydrogenated SBCs are often used to modify polyolefins such as polypropylene, polybutylene and polyethylene. One of the unique characteristics of strongly phase-separated block copolymers such as high molecular weight (>50 000) SEBS and SEPS is their response to shear in the melt. These polymers retain their phase-separated structure well above the Tg of the polystyrene because their order-disorder transition temperatures are above processing temperatures. This phase separation strongly inhibits flow in the absence of shear resulting in infinite viscosity at zero shear rates. The application of shear... 

Reactive compatibihzation in a specially designed twin-screw extruder was carried out compounding maleated polypropylene, PP-MA (0-0.14 wt% MA, with PA-6. During the reaction a di-block copolymer was formed at the interface. As the copolymer content increased from zero to 20 wt%, the number average diameter of PA-6 drops decreased from the initial value d = 20, to d = 0.14 um at 20 wt% copolymer. The concentration dependence of shear viscosity also changed with compatibilization from negative deviation from the log additivity rule, NDB, to positive deviation, PDB [Nishio et al., 1992]. 

TABLE 3 Empirical equations of zero shear rate viscosity rjo on molecular weight of polypropylene... 

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