Vallés Cristina, Abdelkader Amr M, Young Robert J, Kinloch Ian A
School of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
Faraday Discuss. 2014;173:379-90. doi: 10.1039/c4fd00112e.
Graphene shows excellent potential as a structural reinforcement in polymer nanocomposites due to its exceptional mechanical properties. We have shown previously that graphene composites can be analysed using conventional composite theory with the graphene flakes acting as short fillers which have a critical length of ∼3 μm which is required for good reinforcement. Herein, polypropylene (PP) nanocomposites were prepared using electrochemically-exfoliated few layer graphene (FLG) with two different flake diameters (5 μm and 20 μm). The crystallization temperature and degree of crystallinity of the PP were found to increase with the loading of FLG, which suggests that the flakes acted as crystallisation nucleation sites. Mechanical testing showed that the 5 μm flakes behaved as short fillers and reinforced the PP matrix poorly. The modulus of the 20 μm flake composites, however, increased linearly with loading up to 20 wt%, without any of the detrimental aggregation effects seen in other graphene systems. The mechanical data were compared with our previous work on other graphene composite systems and the apparent need to balance the degree of functionalization to improve matrix compatibility whilst not encouraging aggregation is discussed.
由于其优异的机械性能，石墨烯在聚合物纳米复合材料中作为结构增强材料展现出卓越的潜力。我们之前已经表明，石墨烯复合材料可以使用传统的复合材料理论进行分析，其中石墨烯薄片充当短填料，其临界长度约为3μm，这是实现良好增强效果所必需的。在此，使用具有两种不同薄片直径（5μm和20μm）的电化学剥离少层石墨烯（FLG）制备了聚丙烯（PP）纳米复合材料。发现PP的结晶温度和结晶度随着FLG的负载量增加而升高，这表明薄片充当了结晶成核位点。力学测试表明，5μm的薄片表现为短填料，对PP基体的增强效果较差。然而，20μm薄片复合材料的模量在负载量高达20 wt%时随负载量线性增加，没有在其他石墨烯体系中看到的任何有害聚集效应。将力学数据与我们之前关于其他石墨烯复合体系的工作进行了比较，并讨论了明显需要平衡功能化程度以改善基体相容性同时又不促进聚集的问题。
