Role of multi-wall carbon nanotube network in composites to crystallization of isotactic polypropylene matrix
Role of multi-wall carbon nanotube network in composites to crystallization of isotactic polypropylene matrix
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DOI：
10.1016/j.polymer.2007.11.041
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发表时间：
2008-01
期刊：
影响因子：
4.6
通讯作者：
Donghua Xu;Zhigang Wang
中科院分区：
文献类型：
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作者：
Donghua Xu;Zhigang Wang
采用溶液共混法制备了等规聚丙烯（iPP）/多壁碳纳米管（CNTs）复合材料。为了改善碳纳米管与聚丙烯的相容性，提高碳纳米管在聚丙烯基体中的分散性，采用化学接枝法对碳纳米管进行改性。化学修饰的碳纳米管具有约6wt%的接枝烷基链。流变学测量表明，由于CNT网络的形成，CNT在iPP/CNT中引起凝胶化，并且临界凝胶化CNT浓度约为7.4wt%，这被认为是由于在本研究中的低CNT纵横比而导致的高。利用光学显微镜（OM）和差示扫描量热仪（DSC）研究了iPP/CNTs的结晶行为。用光学显微镜（OM）测量了CNT含量小于2.0wt%的iPP/CNTs等温结晶过程中球晶的径向生长速率，结果表明球晶的径向生长速率随CNT含量的增加而减小。Avrami分析表明，当CNT浓度低于临界凝胶浓度时，iPP/CNTs的结晶速率加快，这是因为CNT主要起结晶成核剂的作用，而当CNT浓度高于临界凝胶浓度时，iPP/CNTs的结晶速率变化不明显。因为CNT网络可以形成并且主要用于提供对iPP链向晶体生长前沿的迁移和扩散的限制。
The composites (iPP/CNTs) made of isotactic polypropylene (iPP) and multi-wall carbon nanotubes (CNTs) were prepared by solution blending. To improve compatibility between CNTs and iPP and to enhance dispersion of CNTs in iPP matrix, CNTs were chemically modified by grafting alkyl chains. The chemically modified CNTs had about 6wt% grafted alkyl chains. Rheological measurements indicated that CNTs caused gelation in iPP/CNTs due to CNT network formation and the critical gelation CNT concentration was about 7.4wt%, which was considered to be high due to the low CNT aspect ratio in this study. Crystallization behaviors of iPP/CNTs were studied by using optical microscopy (OM) and differential scanning calorimetry (DSC). Radial growth rates of spherulites during isothermal crystallization of iPP/CNTs with CNT concentrations less than 2.0wt% measured by using OM showed decreasing trends with increasing CNT concentration. Avrami analysis of the exothermic heat flow curves during isothermal crystallization of iPP/CNTs measured by DSC indicated that crystallization rates were accelerated when CNT concentrations were lower than the critical gelation concentration, because CNTs mainly functioned as nucleating agents for crystallization, while crystallization rates did not change obviously when CNT concentrations were higher than the critical gelation concentration, because CNT network could form and mainly functioned to provide restriction to mobility and diffusion of iPP chains to crystal growth fronts.