Grade variation in the rheology of white soft paraffin B.P.

Abstract

Abstract The rheology of six grades of white soft paraffin B.P. at 25° has been investigated using continuous shear viscometry and a creep viscometer. Temperature effects between 25° and 50° have been measured in continuous shear, and activation energies from 14·0 to 25·3 k cal mol−1 (58·6 to 105·9 k J mol−1) have been determined. Working the samples on a triple roller mill at 25° was found to decrease the apparent viscosity and, initially, to increase the yield stress. Five of the grades were linear viscoelastic, one was non-linear viscoelastic. The nature of ductility and its relation to measured rheological parameters have been discussed. Creep viscometry data gave a better correlation with the manufacturer’s data than did continuous shear measurements.