Differential scanning calorimetry, combined with Avrami theory, was used to investigate the kinetics of three steps of the complex crystallization process of poly(N-methyldodecano-12-lactam) (MPA): (1) primary melt crystallization at respective crystallization temperature (T,), (2) additional crystallization at 30degreesC, and (3) recrystallization at 54degreesC. Kinetics of the three steps was discussed with respect to T, The Avrami exponent n of primary melt crystallization decreased between 2.5 and 1.9 in the range of T, values of -10 to 20degreesC, which suggests heterogeneous nucleation, followed by two-dimensional growth, with a larger involvement of homogeneous thermal nucleation at greater super-coolings. The crystallization rate constant k decreased with increasing T, The value of n = 1.5 for additional crystallization implies a two-dimensional diffusion-controlled crystal growth with a suppressed nucleation phase. For T-c values ranging from -10 to 0degreesC and 0 to 20degreesC, k showed weak and quite strong decreasing dependencies on T-c, respectively. The recrystallization mechanism involved partial melting of primary crystallites and two-dimensional rearrangement of chains into a more perfect structure. The rate of this process was almost independent of T-c. The values of activation energies were derived for the three steps of MPA crystallization using the Arrhenius equation. (C) 2004 Wiley Periodicals, Inc.