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Semi‐biodegradable polypropylene/poly(lactic acid) (PLA) (70:30 wt.%) blend with co‐continuous structure was used for the development of conducting composites. Multi‐walled carbon nanotube (CNT) and the noncovalently functionalized CNT with alkylphosphonium‐based ionic liquid (IL‐CNT) were used as conducting fillers. Relative high AC electrical conductivity was achieved by using 1 wt.% of CNT (around 10−3 S/m). This property increased four orders of magnitude when IL‐CNT was employed. The effect of the functionalization with IL on the rheological, morphological and thermal properties was investigated. The DSC analysis also suggested that the filler (CNT or IL‐CNT) exerted strong influence on the cold crystallization of the PLA phase and also on the melt crystallization of the PP phase. The effect of the IL on the dispersion of CNT was also confirmed by rheological measurements and transmission electron microscopy. An increase of the attenuation of the electromagnetic radiation, that is, an improvement of the electromagnetic interference shielding effectiveness (EMI SE) in the X‐band microwave region (8‐12 GHz) was achieved by using IL‐CNT, with an important influence of the absorption mechanism to this property.

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Electrically conductive composites of thermoplastic polyurethane (TPU), poly(vinylidene fluoride) (PVDF), and carbon black-polypyrrole (CB-PPy) were prepared by melt compounding followed by compression molding or by filament production followed by fused filament fabrication (FFF). The storage modulus (G 0 ) and complex viscosity (η*) of the composites increased with the addition of CB-PPy leading to a more rigid material. The electrical and rheological percolation threshold of composites were 5 and 3 wt%, respectively. In fact, composites with 5 wt% or more CB-PPy content display G 0 higher than G 00 indicating a solid-like behavior. Furthermore, the addition of CB-PPy increased the electrical conductivity of all composites. However, the electrical conductivity values of composites containing 5 and 6 wt% of CB-PPy produced by compression molding are one and seven order of magnitude higher than those of FFF composites with same composition. Compression molded and 3D printed composites with 6 wt% of CB-PPy displayed high sensitivity/gauge factor, large measurement range and reproducible piezoresistive response during 100 loading-unloading cycles for both processing methods. The results presented in this study demonstrated the potential use of FFF for producing piezoresistive flexible sensors based on PVDF/TPU/CB-PPy composites.

Multi-walled carbon nanotube (MWCNT) was non-covalently functionalized with room-temperature ionic liquid (IL), 1butyl-3-methyl-imidazolium tetrafluoroborate and blended with epoxy pre-polymer (ER) with the assistance of ultrasonication in the presence of acetone as a diluting medium. The ability of IL in improving the dispersion of MWCNT in epoxy pre-polymer was evidenced by transmission optical microscopy. The corresponding epoxy/MWCNT networks cured with anhydride displayed an increase of the electrical conductivity of around three orders of magnitude with the addition of IL in a proportion of MWCNT/IL 5 1:5 mass ratio. The effect of IL on dynamic mechanical properties and thermal conductivity was also evaluated. The improved thermal and electrical properties was attributed to the better dispersion of MWCNT within the epoxy matrix by IL, evidenced by transmission electron microscopy of the ER/MWCNT networks cured with anhydride. Raman spectroscopy was also used to confirm the interaction between MWCNT and IL.