Isotacticity dependence of spherulitic morphology of isotactic polypropylene
Isotacticity dependence of spherulitic morphology of isotactic polypropylene
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DOI：
10.1016/s0032-3861(97)10208-7
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发表时间：
1998-10
期刊：
影响因子：
4.6
通讯作者：
Koji Yamada;S. Matsumoto;Katsuharu Tagashira;M. Hikosaka
中科院分区：
文献类型：
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作者：
Koji Yamada;S. Matsumoto;Katsuharu Tagashira;M. Hikosaka
研究了等规度在98.9%~ 99.8%之间的等规聚丙烯（iPP）球晶形态与等规度的关系。具有低全同立构规整度[mmmm]= 93.5%的常规iPP用作参考。在125°C-150°C下进行等温结晶。通过偏光显微镜和透射电子显微镜进行形态学观察。几乎所有的球晶都具有α型晶体结构和负双折射（Δn）。由Δn估算的径向片层（R-片层）分数fR随全同立构规整度和结晶温度的增加而增加。这一结果表明，由R-层流和切向层流（T-层流）组成的交叉影线的程度随着全同立构规整度和结晶温度的增加而减小。首次证明了当全同立构规整度最高的样品在150°C结晶时，得到的球晶完全被R-片层占据，即fR = 1。这意味着有很少的交叉阴影lamantae。交叉影线的起源进行了讨论，侧重于分子链内的构型缺陷和分子在结晶过程中的流动性的作用。
The isotacticity dependence of the spherulitic morphology of isotactic polypropylene (iPP) with high isotacticity between 98.9% and 99.8% in isotactic pentad fraction ([mmmm]%) was studied. Conventional iPP with low isotacticity, [mmmm]=93.5%, was used as a reference. Isothermal crystallization was carried out at 125°C–150°C. Morphological observations were carried out by polarizing optical microscopy and transmission electron microscopy. Nearly all the spherulites showed an α-form crystal structure and negative birefringence (Δn). The radial lamellar (R-lamellar) fraction, fR, estimated from Δn increased with increase in isotacticity and crystallization temperature. This result indicates that the degree of cross-hatching composed of R-lamellae and tangential lamellae (T-lamellae) decreased with increase in isotacticity and crystallization temperature. It was shown for the first time that the spherulite fully occupied by R-lamella, i.e. fR≈1, was obtained when the sample with the highest isotacticity was crystallized at 150°C. This means that there are few cross-hatched lamellae. The origin of cross-hatching is discussed, focusing on the role of configurational defects within a molecular chain and the mobility of molecules in the crystallization process.