Surface functionalized carbon nanotubes and its effects on the mechanical properties of epoxy based composites at cryogenic temperature

Epoxies have a wide range of applications in fuel tank fabrication, aerospace, electrical, electronic, and automobile industries. However, these resins are quite brittle, showing poor mechanical performance, especially at cryogenic temperature. The properties of functionalized multi-walled carbon nanotube (MWCNTs)-reinforced epoxy composites were investigated to develop advanced composites for cryogenic use. Two methods were adopted to modify MWCNTs. MWCNTs were first treated by acid mixture, and then maleic anhydride (MA) and isophorone diisocyanate (IPDI) grafting was carried out. At last, the functionalized MWCNTs were integrated into epoxy to prepare MWCNT-reinforced epoxy composites. Raman and XPS analysis proved the effectiveness of acid mixture treatment and confirmed the grafting reaction of MA and IPDI with MWCNTs. TEM analysis indicated that MA and IPDI had been grafted onto the surface of MWCNTs and formed a thin layer. The tensile strength, Young’s modulus, and impact strength of composites at liquid nitrogen temperature (77 K) are all enhanced by the addition of MWCNTs. Results of dynamic mechanical analysis indicated that introducing a small amount of functionalized MWCNTs to epoxy can enhance their storage modulus at 77 K and glass-transition temperature of composites. The results indicated that surface modified MWCNTs can be effectively utilized to enhance the properties of epoxy-based composites at cryogenic temperature.