Thermal decomposition of azo groups of polyamide 6 radical initiator

Thermal decomposition of azo groups of polyamide 6 radical initiators (PA6ini) with molecular weights (M-n) of 5 x 10(3) (PA6ini-1) and 13 x 10(3) (PA6ini-2), which were obtained from a polyamide 6 prepolymer and 4,4'-azobis(4-cyanopentanoyl chloride), was measured by differential scanning calorimetry (DSC) and ultraviolet (UV) absorption in solid state and in solution (formic acid and 2,2,2-trifluoroethanol), respectively. Thermal decomposition of PA6ini in solid state initiated at a lower temperature than that of 4,4'-azobis(4-cyanopentanonic acid) (ACPA), and the peak top temperature of PA6ini decreased with increasing molecular weight. Activation energies of azo group decomposition of PA6ini-1 and PA6ini-2 in solid state were 102.3 kJ mol(-1) and 88.9 kJ mol(-1), respectively. The rate constants of azo group decomposition of ACPA and PA6ini were affected by solvents. The rate constant of azo group decomposition of PA6ini-2 in 2,2,2-trifluoroethanol was significantly influenced by concentrations of PA6ini. Activation energies of azo group decomposition of PA6ini were independent of solvents, and were similar to those in solid state.