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.

中文翻译：

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聚酰胺66及其模型化合物的热降解


N,N'-二丁基己二酰胺和聚酰胺 66 (PA66) 的热降解是在大规模实验装置中进行的，并使用氮气吹扫，以收集难以捉摸的降解中间体。在高氮气流速下，1-丁基氮杂环庚烷-2,7-二酮被确定为 N,N'-二丁基己二酰胺热分解的主要降解产物。加热时，1-丁基氮杂环庚烷-2,7-二酮生成环戊酮及其衍生物、二丁基脲和腈，它们构成了N,N'-二丁基己二酰胺的大部分降解产物，证明7元杂环化合物是关键的初级降解产物产物以及N,N'-二丁基己二酰胺二次降解产物的前体。随后，开发了有关 1-丁基氮杂环己烷-2,7-二酮的生成和分解的化学方法，用于 DBA 的热分解。另一方面，己二胺、1,8-二氮杂环十四烷-2,7-二酮、环戊酮及其衍生物作为PA66热分解的重要降解产物被收集。鉴于DBA和PA66及其可比降解产物的结构相似性，最终建立了以7元环的生成和分解为中心的PA66热降解机制。