The Power-Law Index of Some Neat Plastics

The Power-Law Index of Some Neat Plastics As it was explained in the section Shear-thinning Effect and the Power Law Equation, the higher the deviation of a molten plastic from Newtonian behavior, the lower its power-law index and the steeper the dependence of its viscosity on shear rate. The lower the power-law index, the more sensitive the shear viscosity to flow speed. As it will be shown in this chapter later, the lower the quality of a regrind, the lower (often) its power-law index. As can be seen from Tables 17.4 and 17.5, PVC, PS, ABS, and PMMA have particularly low power-law index compared to PET or PE, hence, that lowers the window of processability for the former plastics in terms of speed. Both the 

TABLE 17.4 The power-law index, shear viscosity, and other useful properties of a number of neat generic polymers [14] 

Polymer The power-law index ( ) Density (g/cc) Glass transition (°C) Melting point (°C) 

TABLE 17.5 The power-law index of certain neat polymers [15] 

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