Abstract The polyamide 12 (PA12) with different crystal forms is prepared with three crystallization paths. The crystal structures and corresponding thermal properties are systematically investigated. The results reveal that an α-form and a mixed (α + γ)-form of PA12 can be obtained by casting at 30°C and (40–80°C), respectively. Meanwhile, the γ-form of PA12 can be obtained by both casting at 90°C and slow melt cooling. However, the γ′-form is obtained only by melt quenching. Both the γ and γ′ forms of PA12 exhibit a single melting peak, whereas the α-form exhibits two melting peaks. The higher peak is attributed to the melting of γ-PA12, which originates from the melting–recrystallization of the α-PA12. It is found that the tensile properties of PA12 depend on the crystal forms. Both the γ and γ′-PA12 are strong and tough polymer materials, while α-PA12 is a strong but brittle polymer material.

中文翻译：

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尼龙 12 的晶体转变和热行为

摘要 通过三种结晶途径制备了不同晶型的聚酰胺12(PA12)。系统地研究了晶体结构和相应的热性能。结果表明，分别在 30°C 和 (40–80°C) 下浇铸可以得到 α 型和混合 (α + γ) 型 PA12。同时，通过在 90°C 下浇铸和缓慢熔体冷却都可以获得 γ 型 PA12。然而，γ'-形式只能通过熔体淬火获得。PA12 的 γ 和 γ' 形式都表现出单个熔化峰，而 α-形式表现出两个熔化峰。较高的峰归因于 γ-PA12 的熔化，它源于 α-PA12 的熔化-再结晶。发现 PA12 的拉伸性能取决于晶型。γ和γ'-PA12都是强韧的高分子材料，