Saturation of Pointlike Nuclei and the Transition to Oriented Structures in Flow-Induced Crystallization of Isotactic Polypropylene
Saturation of Pointlike Nuclei and the Transition to Oriented Structures in Flow-Induced Crystallization of Isotactic Polypropylene
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DOI：
10.1021/ma802479c
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发表时间：
2009-08-11
期刊：
影响因子：
5.5
通讯作者：
Meijer, Han E. H.
中科院分区：
文献类型：
--
作者：
Housmans, Jan-Willem;Steenbakkers, Rudi J. A.;Meijer, Han E. H.
用流变仪研究了分子量和加工条件对等规聚丙烯结晶动力学的影响。流动诱导的结晶实验进行剪切速率下，预期的最长链的分子拉伸。根据油的分子量，观察到的点状核的饱和与增加剪切时间。在大多数情况下，该过程在足够的流动时间后加速，并且这种动力学变化是由于原纤成核的发生，导致行结构和/或shishes的形成。点状核的数量是来自流变学实验通过模拟系统作为一个悬浮液。该方法具有一些重要的优点，即，(1)它适用于光学显微镜不起作用的系统（即，彩色系统）和（2）它比光学方法更容易、更快和更准确。
The influence of molecular weight and processing conditions on the crystallization kinetics of isotactic polypropylene is studied using rheometry. Flow-induced crystallization experiments are performed with shear rates at which molecular stretch of the longest chains is expected. Depending oil the molecular weight, a saturation of pointlike nuclei is observed with increasing shear time. In most cases, the process accelerates after sufficient flow time, and this change in kinetics is due to the occurrence of fibrillar nucleation resulting in the formation of row structures and/or shishes. The number of pointlike nuclei is derived from the rheometry experiments by modeling the system as a suspension. This method has some important advantages, i.e., (1) it is applicable to systems where optical microscopy does not work (i.e., colored systems) and (2) it is much easier, faster, and more accurate than optical methods.