Study on the Prediction of the Solution Viscosities for Nitrile Butadiene Rubber Dissolved in Ester Solvents Under Various Temperatures and Shear Rates

ABSTRACT In this study, three NBR solution systems (NBR/ n ‐butyl acetate, NBR/isobutyl acetate, and NBR/hexyl acetate) were prepared to measure the viscosities using a rotational viscometer. The effects of solvent structure, temperature (25°C–60°C) and shear rate (9.3–186 s −1 ) on the viscosities were examined. The results revealed that the viscosity decreased with increasing temperature and shear rate, and it was significantly influenced by both the alkyl chain length and branching of ester solvents, with the NBR/ n ‐butyl acetate solution showing the highest viscosity (240 mPa s). The viscoflow activation energy ( E η ) of the NBR solutions was calculated by fitting the data to the Arrhenius equation, with the maximum value reaching 16.75 kJ mol −1 . Concurrently, the non‐Newtonian index ( n ) of the NBR solutions was fitted using the power‐law equation with the obtained values of n ranging from 0.9 to 1, reflecting the degree of non‐Newtonian behavior. The Flory–Huggins interaction parameter ( χ HSP ) demonstrated the best compatibility for the NBR/ n ‐butyl acetate solution. A prediction relationship for viscosity was established by correlating with χ HSP ( R 2 > 0.97). This research provides theoretical guidance and data support for the precise regulation of viscosities in rubber manufacturing industries, including adhesives and coatings.