Nucleation and crystallization kinetics of polyamide 12 investigated by fast scanning calorimetry

Nucleation and crystallization of polyamide 12 (PA 12) have been systematically investigated by fast scanning calorimetry at non-isothermal and isothermal conditions. The critical cooling rates of crystallization and crystal nucleation were determined as 300 and 10,000 K/s, respectively. Moreover, the half-times of nucleation (t_1/2,nucl) and overall crystallization (t_1/2,cry) show monomodal and bimodal dependencies on the crystallization temperature. t_1/2,nucl has an approximate minimum value of about 0.0005 s at 333 K, which is about 10–20 K above the glass transition temperature, and t_1/2,cry has two minima of about 0.05 and 0.8 s at about 333 and 383 K, respectively. Comparing the crystallization behavior of PA 12 with other polyamides, the activation energy for crystallization increases and the energy barrier of short-range diffusion decreases with the increase of the amide-group density in the chains.