OBSERVATIONS ON THE DETERMINATION OF POLYAMIDE-6 VISCOSITY NUMBER

The viscometric behaviour of high molecular mass polyamide 6, prepared by activated anionic polymerization of epsilon-caprolactam in a twin- screw extruder, has been studied in 90% formic acid. Results obtained show that viscosity number increases with polymer concentrations to ap proximately 0.001 or 0.001 5 g ml-1, but unexpectedly declines thereaf ter. Whereas anomalous results are obtained at a concentration level o f 0.005 g ml-1, as specified in ISO 307:1984, at very low solution con centration, viscometry data correlate well with findings from g.p.c.