Noncovalent functionalization of carbon nanotubes via co-deposition of tannic acid and polyethyleneimine for reinforcement and conductivity improvement in epoxy composite

In this paper, a novel strategy via one-pot co-deposition of tannic acid (TA) and polyethyleneimine (PEI) to modify the MWCNTs was reported, which allows to modify MWCNTs with polymer via robust linkage in a convenient, green and nondestructive way. The obtained TA-PEI modified MWCNTs (TA-PEI/MWCNTs) with abundant amine and imine groups have good dispersibility in various solvents as well as epoxy resin. Epoxy composites reinforced with TA-PEI/MWCNTs were prepared and their mechanical properties was studied in detail. The modification of MWCNTs by TA-PEI could not only enhance the compatibility of MWCNTs with epoxy resin, but also improve the interface interaction between MWCNTs and epoxy matrix caused by the curing reaction between epoxy and amine groups on MWCNTs surface. With the 0.4 wt% loading of TA-PEI/MWCNTs, the impact strength and tensile strength of the composite reach 40.51 kJ/m2 and 80.83 MPa, improved by 154% and 148% compared with pristine MWCNTs/epoxy composites, respectively, clearly demonstrating the important role of TA-PEI modification. In addition, the glass transition temperature (Tg) of the composite is 152.4 °C which is significantly higher than pure epoxy resin (136.9 °C) and MWCNTs/epoxy (142.0 °C). Furthermore, the electrical conductivity of the epoxy composite was also remarkably enhanced.