最近在查找尼龙12cas号的时候发现了2个号，然后去咨询了cas。
这两个号分别是25038-74-8和24937-16-4，大家可以查询一下，都是PA12，cas的回复如下：
Thank you for contacting the CAS Customer Center. As you noted, both of these numbers refer to a compound with the same chemical formula. However, the compounds are in different conformations. RN 24937-16-4 has a structure that is an open chain configuration, and RN 25038-74-8 refers to a structure that is a closed ring homopolymer.
我想大概的意思是24937-16-4是某个共聚物中间的尼龙12链段，而25038-74-8是尼龙12均聚物，不具有任何其他的改性结构。
英语的表述方法感觉有些难以理解，尼龙12会具有闭环结构吗？聚合以后链段之间已经互相纠缠，应该不存在闭环封端的可能吧？
