CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China , Hefei, Anhui Province 230026, P. R. China.
ACS Appl Mater Interfaces. 2015 Jan 21;7(2):1364-75. doi: 10.1021/am507938s. Epub 2015 Jan 8.
More dominant shear flow effect with different shear rates and shear time with assistance of added carbon nanotubes (CNTs) of low amounts on the crystallization kinetics of isotactic polypropylene (iPP) in CNT/iPP nanocomposites was investigated by applying differential scanning calorimetry (DSC), polarized optical microscopy (POM), and rheometer. CNTs were chemically modified to improve the dispersity in the iPP matrix. CNT/iPP nanocomposites with different CNT contents were prepared by solution blending method. The crystallization kinetics for CNT/iPP nanocomposites under the quiescent condition studied by DSC indicates that the addition of CNTs of low amounts significantly accelerates crystallization of iPP due to heterogeneous nucleating effect of CNTs, whereas a saturation effect exists at above a critical CNT content. The shear-induced crystallization behaviors for CNT/iPP nanocomposites studied by POM and rheometry demonstrate the continuously accelerated crystallization kinetics with assistance from added CNTs, with increasing CNT content, shear rate, and shear time, without any saturation effect. The changes of nucleation density for CNT/iPP nanocomposites under different shear conditions can be quantified by using a space-filling modeling from the rheological measurements, and the results illustrate that the combined effects of added CNTs and shear flow on the acceleration of crystallization kinetics are not additive, but synergetic. The mechanisms for the synergetic effect of added CNTs and shear flow are provided.
通过应用差示扫描量热法（DSC）、偏光显微镜（POM）和流变仪，研究了在加入少量碳纳米管（CNT）的情况下，不同剪切速率和剪切时间对间规聚丙烯（iPP）结晶动力学的剪切流效应。CNT 经过化学改性以提高其在 iPP 基体中的分散性。通过溶液共混法制备了不同 CNT 含量的 CNT/iPP 纳米复合材料。通过 DSC 研究 CNT/iPP 纳米复合材料在静止条件下的结晶动力学表明，由于 CNT 的异相成核效应，少量 CNT 的添加可显著加速 iPP 的结晶，而在超过临界 CNT 含量时存在饱和效应。通过 POM 和流变仪研究 CNT/iPP 纳米复合材料的剪切诱导结晶行为表明，随着 CNT 含量、剪切速率和剪切时间的增加，结晶动力学不断加速，不存在饱和效应。通过流变学测量的空间填充建模，可以定量地研究 CNT/iPP 纳米复合材料在不同剪切条件下的成核密度变化，结果表明，加入的 CNT 和剪切流对结晶动力学加速的综合效应不是加和的，而是协同的。提供了加入 CNT 和剪切流协同效应的机制。
