Polymer melts and solutions elongational viscosities may be measured using non-lubricated flow characteristics through a semi-hyperbolic die The effects of body forces related to developing orientation in the fluid during converging extensional flow are so strong that the shearing contribution become negligible in comparison, eliminating the need for lubrication. The effective elongational viscosities of polypropylene (PP) melts and lyocell solutions correlated with shear-flow determinations were used to estimate the enthalpy and entropy changes as function of processing conditions.
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