Melt recrystallization behavior of carbon-coated melt-drawn oriented isotactic polypropylene thin films
Melt recrystallization behavior of carbon-coated melt-drawn oriented isotactic polypropylene thin films
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DOI：
10.1039/c5py01083g
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发表时间：
2015-10
影响因子：
4.6
通讯作者：
Le Ma;Jie Zhang;M. A. Memon;Xiaoli Sun;Huihui Li;Shouke Yan
中科院分区：
文献类型：
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作者：
Le Ma;Jie Zhang;M. A. Memon;Xiaoli Sun;Huihui Li;Shouke Yan
利用透射电镜结合电子衍射研究了真空碳蒸发熔融拉伸聚丙烯薄膜在不同熔融温度、熔融时间和再结晶温度下的熔融再结晶行为。结果表明，碳包覆熔融拉伸高取向iPP薄膜在制备过程中始终以取向的方式熔融再结晶，结晶片层在垂直于拉伸方向上排列有序。这与真空蒸镀碳膜对iPP表面层取向链茎的强固定作用有关。由于这些固定的iPP链茎最初包含在α-iPP晶格中，它们在重结晶过程中充当α-iPP核，并诱导仅由α-iPP晶体组成的高度取向的iPP层片。这表明，经常报道的取向诱导的β-iPP结晶是一个成核控制的过程。此外，通过比较熔融拉伸iPP薄膜与再结晶薄膜的取向结构，发现拉伸诱导结晶过程中，薄膜的宽角度片层支化现象受到严重抑制，而熔融再结晶过程中，薄膜的宽角度片层支化现象明显。
The melt recrystallization of vacuum carbon evaporated melt-drawn iPP thin films at varying melting temperature, melting time and recrystallization temperature was studied by means of transmission electron microscopy combined with electron diffraction. It was found that the carbon-coated melt-drawn highly oriented iPP thin films melt-recrystallized always in an oriented way with well ordered crystalline lamellae perpendicular to the drawing direction during sample preparation. This is related to the strong fixing effect of the vacuum evaporated carbon film on the oriented iPP chain stems on the surface layer. Since these fixed iPP chain stems are originally included in the α-iPP crystal lattice, they serve as α-iPP nuclei during the recrystallization process and induce highly oriented iPP lamellae composed of only α-iPP crystals. This indicates that the frequently reported orientation-induced β-iPP crystallization is a nucleation controlled process. Moreover, by comparing the original oriented structure of melt-drawn iPP films with the recrystallized ones, it is concluded that the characteristic wide angle lamellar branching is severely suppressed in elongation-induced crystallization, while takes place evidently during melt-recrystallization.