For a polyisobutylene/decalin solution “D2b,” agreement over a range of values of shear rate γ̇ up to 29,000 s−1 (where the stress ratio N1/σ=5;σ=shear stress) is found between values of N1 measured near 20°C using a Torsional Balance Rheometer (“TBR”) and a “Stressmeter” (“SM”, a slit‐die rheometer using transverse slots to measure hole pressures); viscosity values also agree. Time‐temperature superposition behavior exhibited by SM data taken in a temperature range 22–99°C suggest that the range of validity of the SM method for determining N1 approximately extends up to γ̇=1.3×106s−1; here, N1/σ=10 and, in the SM die, the Reynolds number Re=100. This γ̇ value is four times higher than the greatest γ̇ value used in previous similar tests of the SM method made with a similar but more concentrated solution “D2”.

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