摘要：

Specific viscosities of dilute solutions of polyisobutylene fractions decrease approximately linearly with the rate of shear over the range from several hundred to several thousand sec.-1. The "shear coefficient" φ, conveniently defined as 100 × d(ln ηsp)/dγ, is independent of concentration at low concentrations. For molecular weights not exceeding several million, φ is approximately proportional to the square of the intrinsic viscosity (as indicated by measurements on the same polymer fraction in different solvents), and inversely proportional to the molecular weight (as indicated by comparison of φ's in different solvents for polymers of molecular weights so chosen as to give the same intrinsic viscosities in the respective solvents). This empirical relationship is useful for the extrapolation of intrinsic viscosities of polyisobutylene solutions to zero rate of shear. The logarithm of ηsp decreases non-linearly with γ for dilute solutions of polyisobutylene of very high molecular weight (ca. 15 × 106).

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