MECHANISM AND KINETICS OF ADIABATIC ANIONIC-POLYMERIZATION OF EPSILON-CAPROLACTAM IN THE PRESENCE OF VARIOUS ACTIVATORS

Nylon 6 was prepared by adiabatic anionic polymerization of e-caprolac tam using hexamethylene epsilon-dicarbamoyl dicaprolactam (HDC), cyclo hexyl carbamoyl caprolactam (CCC), or phenyl carbamoyl caprolactam (PC C) as activators and sodium caprolactamate (NaCL) as a catalyst at var ious initial reaction temperatures ranging from 130 to 160 degrees C. Adiabatic temperature rise was recorded as a function of polymerizatio n time to investigate polymerization ion kinetics. Kinetic parameters for polymerization, which are more accurate than data reported to date , could be obtained by fitting the temperature rise data with a new po lymerization kinetic equation involving crystallization exotherm and t hermal conduction. The polymerization rate highly depended on the chem ical structure of the activator used, which indicates that the initiat ing step where the activator is attacked nucleophilically by NaCL is a very important reaction step, affecting the overall polymerization ra te. CCC showed the fastest polymerization rate, whereas HDC and PCC sh owed the medium and the slowest rate, respectively. The contributions of crystallization exotherm and thermal conduction to the resultant te mperature rise during polymerization were significant, when the initia l reaction temperature was lower than 140 degrees C. In all cases, the molecular weight obtained from intrinsic viscosity measurement was gr eater than the expected molecular weight. This may be attributed to th e branching and/or crosslinking reaction through Claisen-type condensa tion reactions. (C) 1995 John Wiley & Sons, Inc.