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首页> 外文期刊>Journal of Applied Polymer Science >Crystallization of Isotactic Polypropylene inside Dense Networks of Carbon Nanofillers
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Crystallization of Isotactic Polypropylene inside Dense Networks of Carbon Nanofillers

机译：碳纳米填料密集网络内部全同立构聚丙烯的结晶

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In this study, we performed the crystallization of carbon nanotube (CNT)/isotactic polypropylene (iPP) and graphene nanosheet (GNS)/iPP composites with very high nanofiller loadings; these are frequently used in polymer composites for electromagnetic interference shielding and thermal conductivity. Rheology testing indicated that both the high-loading CNTs and GNSs formed dense networks in the iPP matrix, and transmission electron microscopy showed that their connection types were completely different: the CNTs contacted one another in a dot-to-dot manner, whereas the GNSs linked reciprocally in a plane-to-plane manner. The carbon nanofiller networks brought about two opposite effects on iPP crystallization: a nucleation effect and a confinement effect. The CNT network showed a stronger nucleation effect; however, the CNT network also revealed a more powerful confinement effect because the CNT network was denser than the GNS network. With increasing content of the carbon nanofillers, the crystallization rates of both the CNT and GNS composites first increased, then decreased, and showed a very high saturation concentration at 50 wt %; this resulted from the competitive relationship between the nucleation effect and confinement effect. The crystallization was facilitated when the carbon nanofiller concentration was below saturation, where the nucleation effect invariably played a dominant role. Although the crystallization was depressed when the carbon nanofiller concentration was above saturation, the nucleation effect was subdued, and the confinement effect was extensive. Compared to the GNS/iPP composites, the CNT/iPP composites showed a more depressed crystallization. The suppression mechanism is discussed with consideration of the local topological structure constructed by those two carbon nanofillers.
机译：在这项研究中，我们进行了具有很高纳米填料填充量的碳纳米管（CNT）/全同立构聚丙烯（iPP）和石墨烯纳米片（GNS）/ iPP复合材料的结晶。这些通常用于聚合物复合材料中，以屏蔽电磁干扰和导热。流变学测试表明，高载荷的CNT和GNS在iPP基质中均形成致密的网络，透射电子显微镜显示它们的连接类型完全不同：CNT以点对点的方式相互接触，而GNS以平面间的方式相互连接。碳纳米填料网络对iPP结晶产生了两个相反的影响：成核作用和限制作用。碳纳米管网络显示出更强的成核作用。但是，由于CNT网络比GNS网络更密集，因此CNT网络还显示出更强大的约束效果。随着碳纳米填料含量的增加，CNT和GNS复合材料的结晶速率均先升高，然后降低，并在50 wt％时显示出很高的饱和浓度。这是由于成核效应和约束效应之间的竞争关系所致。当碳纳米填料的浓度低于饱和时，促进了结晶，其中成核作用始终起主导作用。尽管当碳纳米填料浓度高于饱和时结晶被抑制，但是成核作用减弱，并且限制作用是广泛的。与GNS / iPP复合材料相比，CNT / iPP复合材料的结晶度更低。讨论了抑制机理，并考虑了由这两个碳纳米填料构成的局部拓扑结构。

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