The influence of carbon nanotubes and exfoliated graphite nanoplatelets modified by phosphonium‐based ionic liquids on polyurethane composites

Abstract The effect of the non‐covalent modification of carbon nanotubes (CNTs) and exfoliated graphite nanoplatelets (xGnP) with phosphonium‐based ionic liquids (ILs) on the polyurethane (PU) matrix was investigated. The two ILs used in this work were trihexyl(tetradecyl)phosphonium chloride (IL 101) and trihexyl(tetradecyl) phosphonium dicyanamide (IL 105). The electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of PU/CNTs and PU/xGnP composites was strongly influenced upon the loading and dispersion of the conductive fillers in the polymer matrix, as well as the amount and the chemical nature of IL. PU/IL‐xGnP and PU/IL‐CNTs show higher electrical conductivity and EMI SE values when compared to those composites comprising PU matrix with non‐modified fillers. Furthermore, the composites containing modified fillers with IL105 exhibited higher electrical conductivity and EMI SE values than those with IL101. This behavior was due to the better interaction of the dicyanamide counter anion (IL 105), which interacts more efficiently with the PU matrix than the chloride anion (IL 101). The hybrid composites (PU/IL‐CNT/IL‐xGnP) displayed higher electrical conductivity and EMI SE than those found for hybrid composites without ILs. Hybrid composite with a proportion of 75/25 of CNT/xGnP modified with IL 105, displayed EMI SE values adequate for commercial applications. These results highlight that these hybrid composites containing CNT/xGnP modified with trihexyl(tetradecyl) phosphonium dicyanamide are promising materials for electromagnetic shielding.