Thermal and X‐ray analysis of polymorphic crystals, melting, and crystalline transformation in poly(butylene adipate)
Thermal and X‐ray analysis of polymorphic crystals, melting, and crystalline transformation in poly(butylene adipate)
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DOI：
10.1002/polb.20470
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发表时间：
2005-07
期刊：
影响因子：
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通讯作者：
E. Woo;Ming-Chien Wu
中科院分区：
文献类型：
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作者：
E. Woo;Ming-Chien Wu
通过广角 X 射线衍射 (WAXD) 和差示扫描量热法 (DSC) 彻底检查了脂肪族可生物降解聚酯聚己二酸丁二醇酯 (PBA) 中的多晶型晶体和复杂的多重熔融行为。尝试进一步阐明与 PBA 中多晶型晶型相关的多个熔融峰的机制。更稳定的 α 型晶体通常有利于在较高温度 (31–35 °C) 下从熔体中结晶，或在从熔体中缓慢冷却时；而β-形式是在低温（25-28°C）下结晶的首选物种。我们进一步证明，如果 PBA 结晶时存在先前的 α 型核，即使在低温（25-28 °C）下，PBA 结晶也可以产生所有 α 型。含有两种晶型的 PBA 可以显示多达四个熔融峰（P1 ～ P4，按温度升序排列）。然而，最初仅含有 α 晶体的 PBA 表现出 P1 和 P3 双熔化峰，这归因于 α 晶体的双层状分布。相比之下，最初仅包含 β 晶体的 PBA 在扫描时也可能表现出双熔解峰（P2 和 P4）。虽然 P2 显然与初始 β 晶体的熔化有关，但第四个熔化峰 (P4) 看起来相当宽，被确定与从 β 晶体转变为 α 晶体的叠加热事件以及新重组 α 晶体的最终重新熔化有关。分析了从一种到另一种或相反的晶体转变、片层增厚、熔融状态退火以及对 PBA 晶体多晶型的影响。讨论了 PBA 中分离的 α 或 β 晶体双峰的关系和机制。 © 2005 Wiley periodicals, Inc. J Polym Sci B 部分：Polym Phys 43: 1662–1672, 2005
Polymorphic crystals and complex multiple melting behavior in an aliphatic biodegradable polyester, poly(butylene adipate) (PBA), were thoroughly examined by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Further clarification on mechanisms of multiple melting peaks related to polymorphic crystal forms in PBA was attempted. More stable α-form crystal is normally favored for crystallization from melt at higher temperatures (31–35 °C), or upon slow cooling from the melt; while the β-form is the favored species for crystallization at low temperatures (25–28 °C). We further proved that PBA crystallization could also result in all α-form even at low temperatures (25–28 °C) if it crystallized with the presence of prior α-form nuclei. PBA packed with both crystal forms could display as many as four melting peaks (P1 ˜ P4, in ascending temperature order). However, PBA initially containing only the α-crystal exhibited dual melting peaks of P1 and P3, which are attributed to dual lamellar distributions of the α-crystal. By contrast, PBA initially containing only the β-crystal could also exhibit dual melting peaks (P2 and P4) upon scanning. While P2 is clearly associated with melting of the initial β-crystal, the fourth melting peak (P4), appearing rather broad, was determined to be associated with superimposed thermal events of crystal transformation from β- to α-crystal and final re-melting of the new re-organized α-crystal. Crystal transformation from one to the other or vice versa, lamellae thickening, annealing at molten state, and influence on crystal polymorphism in PBA were analyzed. Relationships and mechanisms of dual peaks for isolate α- or β-crystals in PBA are discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1662–1672, 2005