Crystallization and Melting of Oriented Parent–Daughter Lamellae in Sheared Isotactic Poly(propylene)
Crystallization and Melting of Oriented Parent–Daughter Lamellae in Sheared Isotactic Poly(propylene)
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DOI：
10.1071/ch10080
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发表时间：
2010-08
影响因子：
1.1
通讯作者：
Andrew J. K. Phillips;P. Zhu;C. Hadinata;G. Edward
中科院分区：
文献类型：
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作者：
Andrew J. K. Phillips;P. Zhu;C. Hadinata;G. Edward
α-等规聚(丙烯)(α-IPP)表现出一种片层支化形式，这种支化形式在半结晶聚合物中是独一无二的，其中支链与原始晶片具有明显的取向关系。这被称为亲女关系(PD)。通过允许结构以取向的形式结晶，形成了双峰取向的片层，并且可以用广角X射线散射(WAXS)观察到Pd片层的单独贡献。本研究用时间分辨流变仪研究了流动诱导结晶和随后的熔化过程中取向的Pd片层。在结晶过程中，观察到子晶片的平面随着它们从母晶片的生长而向流动方向弯曲。这是由于邻近的女儿片层的影响限制了它们的生长方向。取向子片的熔融温度比取向母片低~5℃，这为剪切α-iPP熔融热图中观察到的多重熔融行为提供了新的解释。
Alpha isotactic poly(propylene) (α-iPP) exhibits a form of lamellar branching that is unique among semicrystalline polymers, where the branches have a distinct orientation relationship with the original crystalline lamellae. This is termed a parent–daughter relationship (PD). By allowing the structure to crystallize in an oriented form, a bimodal orientation of lamellae is developed and the individual contributions of PD lamellae can be observed using wide-angle X-ray scattering (WAXS). The present study investigated oriented PD lamellae during flow-induced crystallization and subsequent melting using time resolved rheo-WAXS. During crystallization the planes of the daughter lamellae were observed to curve towards the flow direction as they grew from their parent lamellae. This was explained by the influence of neighbouring daughter lamellae confining their growth direction. Oriented daughter lamellae were found to melt ~5°C lower than oriented parent lamellae, which provides a new explanation for the multiple melting behaviour observed in the melting thermograms of sheared α-iPP.