A Correlation of Normal Stress Data for Polyisobutylene Solutions

A survey of normal stress measurements for polyisobutylene fluids is made. The first normal stress ${\mathrm{(N}}_1)$ data are correlated with $N_1{c}^2{\mathrm{/\tau }}^2$ as a very weak function of concentration (c), molecular weight (M), and shear stress (τ). We also find the second normal stress as about −0.15 of $N_1.$ The limitations of this empirical correlation are discussed.