Amide‐exchange reactions in mixtures of <i>N</i>‐alkyl amides and in polyamide melt blends

Abstract

Abstract The amide‐exchange reactions which cause copolymer formation in polyamide melt blends were studied with mixtures of N ‐ethylcaproamide and N ‐hexylacetamide containing small concentrations of caproic acid and hexylamine as a model system for melt blends of aliphatic polyamides. Amide exchange was found to involve acidolysis and aminolysis reactions with no detectable contribution of direct reaction between amide groups. Kinetics data are consistent with formation of an anhydride intermediate in amide acidolysis. Rate constants over the range 200–275°C and activation energies for amide acidolysis and aminolysis reactions are given. Equations are given for calculating amide exchange rates in polyamide melt blends and for relating degree of amide exchange to block copolymer composition.