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A. Kloziński

Evaluation of the Reynolds number in rheological measurements of polyethylene

Polimery 2010, No 7/8, 575


DOI: dx.doi.org/10.14314/polimery.2010.575

Summary

The determination of the Reynolds number from experiments performed under real extrusion conditions with an extrusion Rheometer equipped with special cylindrical heads and exchangeable dies of varying L/D ratios has been presented. Low density (PE-LD FABS 23-D 022), middle density (PE-MD HF513) polyethylene and a blend of equal amounts of both were chosen for the rheological studies. The influence of the die dimensions and the properties of the extruded polymers on the Reynolds number was evaluated. The flow parameters were determined on the basis of the Reynolds number (Re) which was estimated on the basis of the average linear flow velocity. In spite of the high flow velocity of the polymer, attaining even 0.30m/s for PE-LD through a die 20mm in length and 2mm in diameter, a laminar flow was maintained. A comparative analysis revealed significant changes of the Reynolds number resulting from the different values of the power flow index (n) and the consistency index (k). The determination of the flow curves also allowed for the evaluation of the dependence between the Re values and the viscosity η of the studied polymers.


Key words: rheological measurements, Reynolds number, flow velocity, power law index, consistency index, polyethylene, polymer blends


e-mail: Arkadiusz.Klozinski@put.poznan.pl


A. Kloziński

Evaluation of the Reynolds number in rheological measurements of polyethylene