Graphene nanoplatelet-modified epoxy: effect of aspect ratio and surface functionality on mechanical properties and toughening mechanisms
Graphene nanoplatelet-modified epoxy: effect of aspect ratio and surface functionality on mechanical properties and toughening mechanisms
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DOI：
10.1007/s10853-016-0160-9
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发表时间：
2016-10-01
影响因子：
4.5
通讯作者：
Taylor, A. C.
中科院分区：
文献类型：
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作者：
Chong, H. M.;Hinder, S. J.;Taylor, A. C.
当石墨烯与环氧聚合物结合时，有可能作为粘合剂或纤维复合材料的高性能增强剂。然而，目前它大多不是以单一的高纵横比薄片的形式提供，而是以石墨烯纳米片层(GNPs)的形式提供，GNPs由成堆的石墨烯薄片组成。一系列横向尺寸、厚度、长宽比和表面官能度的GNP被用来改性一种酸酐固化的环氧聚合物。研究了这些改性环氧树脂的形态、力学性能和增韧机理。GNPs在四氢呋喃(THF)或N-甲基吡咯烷酮(NMP)中超声处理，以促进其在环氧树脂中的分散。四氢呋喃的使用导致了较大的团聚，而对于NMP，观察到了更分散的GNPs堆栈。测试了中间片层尺寸约为4µm的改性环氧树脂的最大模数(1 wt%时为3.6 Gpa)和断裂能(343 J/m(2))，而未改性环氧树脂分别为2.9 Gpa和96 J/m(2)。杨氏模量高度依赖于分散质量，而断裂能与GNP分散程度无关。分散在四氢呋喃中的大颗粒GNPs通过裂纹偏转增韧环氧树脂，而分散在NMP中的GNPs颗粒则表现为片状脱粘、拔出和环氧树脂的塑性空穴增长。这项工作表明，与传统的改性剂相比，可以在低得多的含量下实现增强和增韧。此外，实现良好的分散性对这些材料的工程应用至关重要，而中等尺寸的石墨烯实现了性能的最佳平衡。
Graphene has the potential to act as a high-performance reinforcement for adhesives or fibre composites when combined with epoxy polymer. However, it is currently mostly available not as single high aspect ratio sheets but as graphene nanoplatelets (GNPs), comprising stacks of graphene sheets. GNPs of a range of lateral size, thickness, aspect ratio and surface functionality were used to modify an anhydride-cured epoxy polymer. The morphology, mechanical properties and toughening mechanisms of these modified epoxies were investigated. The GNPs were sonicated in tetrahydrofuran (THF) or n-methylpyrrolidone (NMP) to facilitate dispersion in the epoxy. The use of THF resulted in large agglomerates, whereas more finely dispersed stacks of GNPs were observed for NMP. The maximum values of modulus (3.6 GPa at 1 wt%) and fracture energy (343 J/m(2) at 2 wt%) were measured for the epoxy modified with an intermediate platelet size of approximately 4 mu m, compared to 2.9 GPa and 96 J/m(2); respectively, for the unmodified epoxy. The Young's modulus was highly dependent on the dispersion quality, whereas the fracture energy was independent of the degree of GNP dispersion. The larger agglomerates of the GNPs which were dispersed in THF toughened the epoxy by crack deflection, whereas the GNPs dispersed in NMP showed platelet debonding, pull-out and plastic void growth of the epoxy. This work indicates that reinforcement and toughening can be achieved at much lower contents than for conventional modifiers. Further, achieving a good dispersion is crucial to the engineering application of these materials, and intermediate-sized graphene achieves the best balance of properties.