POLYAMIDES FROM LACTAMS VIA ANIONIC RING-OPENING POLYMERIZATION .2. KINETICS

This paper summarizes a study of the kinetics of the anionic polymeriz ation of caprolactam employing a bisimide (isophthaloyl-bis-caprolacta m) as the initiator and caprolactam-magnesium-bromide as the catalyst. The early part of this investigation was devoted to the study of phen omenological polymerization kinetics via the adiabatic reactor method. Kinetic constants were determined by regression analysis using Malkin 's autocatalytic model. The adiabatic temperature rise normally occurs in two stages. The first rise of about 50 degrees C is due to the pol ymerization exotherm and is followed by a second, smaller temperature rise of about 10 degrees C attributed to the polymer crystallization. (For the purpose of comparison, it should be noted that the typical ad iabatic temperature rise of either polyester or vinyl-ester resin is a bout 150 degrees C). The onset of crystallization is typically precede d by an induction period. The magnitude of temperature rise and the on set of crystallization (including the induction period) is dependent u pon the initial polymerization temperature. In the 117-140 degrees C t emperature range, the correlation between the experimental and predict ed polymerization and crystallization exotherms was excellent. At high er initial temperature (157 degrees C), the polymerization exotherm wa s only 40 degrees C and the crystallization exotherm was not observed. (C) 1997 Elsevier Science Ltd.