Polypropylene grades

Studies of melt flow properties of polypropylene indicate that it is more non-Newtonian than polyethylene in that the apparent viscosity declines more rapidly with increase in shear rate. The melt viscosity is also more sensitive to temperature. Van der Wegt has shown that if the log (apparent viscosity) is plotted against log (shear stress) for a number of polypropylene grades differing in molecular weight, molecular weight distribution and measured at different temperatures the curves obtained have practically the same shape and differ only in position. 

Polypropylene grades manufactured using Ziegler-Natta catalysts are predominandy isotactic, with a comparatively broad molecular weight distribution (Afw/Mn 3.5). Ziegler-Natta catalyzed polypropylene comprises the majority of commodity grade resins. 

The launch of new resins being rare, progress on materials intended for medical applications is by way of formulation, alloys and modifications of existing resins. Thus, new radiation-stable polypropylene grades are available for the manufacture of cups, boxes, baskets, mixers, etc. that are radiation sterilized. And polyesters with better environmental stress cracking resistance are extending their potenti in the area of medical testing. 

In contrast to polyethylene production, solution polymerisation at high temperature is rarely applied for isotactic polypropylene, but some special-purpose polypropylene grades are manufactured (Figure 3.57) [51]. However, the solution process, which yields isotactic polypropylene with a very low level of impurities, is characterised by high overall costs. The solution process is being used to make atactic polypropylene, to which it seems more suited [43],... 

Product-wise, the versatility of the Spherizone process is demonstrated by the high-quality product range that includes all standard polypropylene grades, as well as many unique, special products. One key to this versatility is, as mentioned above, the unique design and operation of the MZCR, which, with a very broad range of feasible process conditions, allows for many kinds of polymer structures as well as intimately mixed polymer compositions to be produced. 

As shown in Fig. 2, commercially available polypropylene grades have a melt viscosity which is either lower than, or equal to, that of ethylene-propylene rubbers. ... 

Polypropylene grade Surface towards striker Falling weight impact strength at 23 °C - J (F,o) Specimen thickness (mm)... 

Two percent by weight of a well-dispersed carbon black of fine particles in the range 15-40 pm should extend to outdoor life of most low-density polyethylene and all polypropylene grades to as much as 20 years in temperature climates and 76 years in tropical climates. Other pigments will have a much lower protective effect than carbon black. 

Elastomer modified polypropylene grades for injection molding. DSM 1991. 0-08-04-01. 

Polypropylene Grade Characteristics Typically 50-100 Grades per producer. 

According to the test, the reference polypropylene grade is quite brittle already in room temperature. This is not surprising since the particular homopolymer is designed for high capacitor film use. Standard deviation of the data (N=5) is less than 5% for the matrix polymer and >10% for the samples containing PIB-silica. 

Nevertheless, although the mechanical properties of the 4 materials are very similar, monitoring of the straining experiments by SAXS has shown that the semicrystalline nanostructure and its evolution vary considerably. The relative variations from material to material indicate that the dominant troublesome effect of blending MMT and the studied metallocene polypropylene grade is not the interfacial incompatibility between filler and matrix, but the alteration of the adjusted nanostructure of the matrix grade by the filler. 

Chemical compatibilization [21, 78, 79] appears to be a secondary effect with the studied polypropylene grade. In fact, the predominant deterioration of mechanical properties of PP by nucleating mineral fillers has been reported in the literature [80]. 

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