Broad Shear Range Viscometry of High Polymer Solutions: Polystyrene and Polyisobutene in Decalin

Abstract

The flow behavior at 25°C for decalin solutions of polystyrenes (PS) of molecular weights up to 7 x 10⁶ and polyisobutenes (PIB) of molecular weights up to 3 x 10⁶ was examined over a wide range of shear rate up to about 10⁵ sec^-1 for several polymer concentr: ations. Measurements involved conventional glass capillary viscometers, a Rheometric Mechanical Spectrometer, and custombuilt high-shear concentric cylinder viscometer. Low shear Newtonian viscosities for the higher concentration entanglement region follow the forms η₀ = CM^0.57 for PS and η₀ = CM⁰-⁶⁸ for PIB. Gel permeation chromatography was used to determine polymer molecular weight, its distribution, and possible change on shearing. Shear degradation was observed for polymers at high values of concentration, molecular weight, and shear stress.