J.G. Oldroyd's early ideas leading to the modern understanding of wall slip

Abstract

In this paper J.G. Oldroyd's ideas leading to the modern understanding of wall slip phenomena are discussed. The procedure proposed by Oldroyd to analyze experimental data that imply the presence of slip is illustrated to (i) determine the slip velocity as a function of wall shear stress and (ii) to recover the true rheological parameters of the material in the absence of slip. The Oldroyd method is demonstrated by using capillary data for a Thermoplastic Vulcanizate (TPV) polymer melt and a bread dough.