Compressional effects in the capillary flow of polycarbonate

摘要

AbstractRecently, the characteristics for pressure corrections in capillary flow have been detailed. The apparent viscosity increases with increasing capillary shear rate for polystyrene and for poly(methyl methacrylate) have been previously explained using free volume theory. These general methods have been developed further in this work and applied to the non‐Newtonian flow of a new system, the polycarbonate of bisphenol A. The pressure correction for up to 2 kilobars will be shown to linearize the capillary pressure drop versus the parameterL/D, capillary length over diameter. This correction eliminates the viscosity difference due to variations inL/Dratio. It is also observed that the zero‐shear viscosity obtained by the extrapolation of the corrected capillary flow curves agrees well with new and independent data on the same polycarbonate obtained using a Weissenberg rheogoniometer. The flow data have been compared with theories and with earlier published data on the same polymer. The two sets of data are not concordant. These new and corrected shear‐dependent data are, however, shown to be expressed qualitatively by the theory of Graessley, using the most probable molecular weight distrib