Integration of single-walled carbon nanotubes into a single component epoxy resin and an industrial epoxy resin system

摘要

Single-walled carbon nanotubes (SWCNT) exhibit exceptional mechanical, thermal and electrical properties, amongst the best of any known material. Combined with their very high aspect ratios, SWCNT are ideal fillers for the fabrication of ultralight multifunctional and structural composite materials with superlative properties. Therefore, over the past decade, a huge amount of effort has been expended exploring potential applications of SWCNT in different polymer matrices including PMMA (1), vinyl ester (2), Nylon (3), Epoxy resin (4) etc., to enhance their mechanical properties as well as their electrical and thermal conductivities. Unfortunately, as a result of strong van der Waals interactions, high crystallinity and aromaticity, SWCNT bundle together as ropes and have little affinity for, or compatibility with, any matrices and solvents. This makes the reinforcement of nanocomposites very challenging unless proper chemistry is employed. It is now widely accepted that chemistry is central to the proper integration of SWCNT into various matrices. Not only does chemistry address problems related to dispersion, it also resolves difficulties with interfacial compatibility. The latter is particularly important if one is seeking improvement of mechanical properties. Penicaud et al. reported that SWCNT bundles can be readily exfoliated by reduction with an alkali metal such as Na, Li or K in THF through electron transfer mediated by alkali-naphthalene-THF complexes (5). Furthermore, they concluded that the thus-reduced SWCNT dissolve spontaneously in polar aprotic solvents such as sulfolane, dimethyl sulfoxide (DMSO), N-methylformamide (NMF), dimethylformamide (DMF), and 1-methyl-2-pyrrolidone. Indeed, these solvents do appear to dissolve reduced SWCNT and therefore, they have been used to conduct chemistry (6-7). Our previous work demonstrated that care must be taken in choosing the proper solvent for reduced SWCNT, particularly in DMSO. Reduced SWCNT have increased nucleophilicity and are easily exfoliated in solution, thus allowing for versatile chemistries to be employed. However, reduced SWCNT can also act as initiators of radical reactions with radical scavengers such as DMSO. Our evidence has shown that DMSO cannot be used as a solvent with reduced SWCNT without first quenching their negative character (8). Therefore, care must also be taken to maintain this negative character and its nucleophilic ability. In this work, covalent chemistry is applied to integrate reduced SWCNT into a single component epoxy resin (MY0510), which was used as test bed, as well as in an epoxy resin system commercially used in industrial scale processes. Preliminary impact, compression after impact and fracture toughness test results for the modified resin and carbon fibre composites are reported and discussed.