ABSTRACT
Theviscosityofallthermoplasticmeltsisnon-Newtonian,i.e.,theviscosityis afunctionoftheshearrateatwhichitistested.Forthisreasongreatcaremust betakentodefinedeformationalconditionswhendiscussingviscosities.Forpurposesofcomparisontheviscositiesofpolymersarefrequentlyquotedinterms oftheirapparentviscosityatzeroshearrate.Zeroshearviscosityisnotadirectly measurablevalue,butitcanbeobtainedbyextrapolationfromobservedviscositiesoverarangeoffiniteshearrates.
