Alkaline polymerization of caprolactam. IV. Equilibrium and degradation with alkaline polymers of caprolactam

Abstract

Abstract The change in the intrinsic viscosity brought about by heating samples of alkalipolymerized polycaprolactam to 220–250°C. for extended periods has been investigated. The polymer samples were obtained by the catalytic action of the sodium salt of caprolactam. The experimental results shows that the intrinsic viscosity of the polymer decreases over the course of about 50 hours, but remains constant after this time. The equilibrium value of the intrinsic viscosity depends on the concentration of the catalyst and on the temperature. The viscosity drop at the beginning of the period of heating is due to the change of the original very unstable broad molecular weight distribution to the equilibrium distribution. Only basic groups, but no carboxyl groups, were detected. The concentration of basic groups remains constant, within the limits of experimental error, over the period required to reach the final value of the intrinsic viscosity.