Viscosities of concentrated polymer solutions. II. Polyisobutylene

Abstract

The steady-flow viscosities of solutions of eight samples of polyisobutylene (four unfractionated, three rough fractions, and one sharp fraction), ranging in viscosity-average molecular weight from 0.32 to 4.0 million, have been measured in three resolvents: five samples in xylene, three in Decalin, and one in a mixture of Decalin and cyclohexanol. The logarithm of the viscosity is not quite a linear function of the reciprocal absolute temperature. The apparent heat of activation for viscous flow at 25°C. increases with concentration in each solvent, approximately linearly with c 2 (grams of polymer per cubic centimeters of solution) above c 2 = 0.1. The dependence of viscosity in poises at 25° on concentration, molecular weight ( M), and solvent viscosity ( η 0) can be expressed by the empirical equation log η = log η 0 − 11.0 + 5.0 log c 2 + 3.4 log M, over a range of log η from 0 to 6. The relations between this equation and other empirical viscosity expressions are discussed.