Thermal degradation of polyamide 66 and its model compound

Thermal degradation of N, N'-dibutyladipamide and polyamide 66 (PA66) was carried out in a large-scale experimental setup with nitrogen sweeping in order to collect elusive degradation intermediates. At a high nitrogen flow rate, 1-butylazepane-2,7-dione was identified as a major degradation product from the thermal decomposition of N, N'-dibutyladipamide. Upon heating, 1-butylazepane-2,7-dione produced cyclopentanone and its derivatives, dibutylurea and a nitrile that constituted the majority of degradation products of N, N'-dibutyladipamide, proving that the 7-membered heterocycle compound is a crucial primary degradation product as well as a precursor for the secondary degradation products of N, N'-dibutyladipamide. Subsequently, chemistry concerning the generation and decomposition of 1-butylazepane-2,7-dione was developed for the thermal decomposition of DBA. On the other hand, hexamethylenediamine, 1,8-diazacyclotetradecane-2,7-dione, cyclopentanone and its derivatives were collected as important degradation products from the thermal decomposition of PA66. In view of the structural similarity between DBA and PA66 and their comparable degradation products, a mechanism centering on the generation and decomposition of a 7-membered ring has ultimately been established for thermal degradation of PA66.