Abstract: During the hydrolysis process of caprolactam to produce polyamide 6, a considerable number of cyclic oligomers are inevitably formed. Among these, the cyclic dimer, with its propensity for aggregation, poses significant challenges to both process safety and product quality. Thus, understanding the characteristics of cyclic oligomers is crucial for ensuring process safety and enhancing product quality. This paper employs a personification approach to vividly describe the properties of cyclic oligomers, elucidating the formation mechanism of cyclic dimers, delineating the behavior of crystal phase transitions, and highlighting the detrimental effects of cyclic dimers on industrial production. Moreover, it proposes methods for process optimization.

Key words: Caprolactam cyclic oligomer, Cyclic dimer, Crystal phase transformation, Performance, Industrial impact