Polypropylene extensional viscosity

Figure 10.3 Master curve of extensional viscosity versus extensional rate for polypropylene showing the effect of fillers on the master curve. 

Figure 10.19 shows the extensional viscosity data of Laun and Munstedt [187] for several low-density polyethylenes made in tubular reactor. We note that these branched polymers are Newtonian at low strain rates, become extension thickening at higher strain rates, and finally exhibit extension thinning. This is similar to the behavior observed by Kurzbeck ef a. [ 184] for a crossKnked polypropylene. In Chapter 11, it will be shown that the pom-pom model predicts this type of extensional viscosity curve. 

Demonstrations are given of the importance of extensional or elongational viscosity in the foam process. New polypropylenes are compared in extensional flow and it is shown how rheological differences allow the prodnction of low density foam on tandem extrnsion equipment. 6 refs. 

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