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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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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.

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.

In this work, immiscible poly(lactic acid) (PLA)/poly(ethylene vinyl acetate) (EVA) composites with 1 phr of multi-walled carbon nanotube (CNT) and different concentration of protonic-based imidazolium ionic liquid (mimbSO 3 H•Cl) were prepared. The protonic ionic liquid (IL) was able to act as dispersing agent for CNT and as compatibilizing agent for the PLA/EVA blend. The multicomponent nanocomposites from the mixture of PLA and EVA containing CNT functionalized with ionic liquid, IL (CNT/ILSO 3 H) were characterized by mechanical and dynamic-mechanical (DMA) tests, electrical conductivity analyses, differential scanning calorimetry (DSC), X-ray diffraction analysis and rheological measurements, as well as chromatographic gel permeation (GPC), and scanning electron microscopy (SEM). The non-covalent functionalization CNT resulted in composites with outstanding electrical and dielectric properties. The high dispersion of CNT promoted by the IL resulted in the formation of a physical networked structure, which was responsible for the higher electrical conductivity and higher melt viscosity. The crystallization process of PLA phase was improved with the presence of CNT/ILSO 3 H. The degradation process during the transesterification reaction did not significantly affect the mechanical properties. The present work highlights the dual role of the IL as compatibilizing and dispersing agent and opens new perspectives for developing new conducting systems with low percolation threshold based on the good dispersion of CNT and the confinement of the filler within a phase of a multiphasic polymeric system.

Poly(vinylidene fluoride) (PVDF) based composites loaded with 3 wt% of carbon black (CB), graphite (GF), and the hybrid CB/GF (1.5/1.5 wt%) were prepared by melt mixing and tested as microwave absorbing material at X-band frequencies (8-12 GHz). The materials were processed and pressed at 220 C into plates of 20 × 20 × 0.1 cm 3. Dielectric and magnetic properties were evaluated using the wave-guide accessory to simulate the reflectivity of singlelayered PVDF composites through impedance matching behavior. The best absorbing properties were achieved with the composite loaded with the CB/GF hybrid material, whose maximum of radiation attenuation of −33 dB at 9.3 GHz was predicted with 4 mm thickness. Afterwards, the reflectivity of sandwiched structures (20 × 20 cm 2 in size) with one-layer honeycomb core sandwiched by two plates of PVDF composites was measured. The PVDF/HBhoneycomb-PVDF/HB structure reached reflection loss = −12 dB (E a = 94%) on a broadband frequency. CB/GF hybrid material in PVDF composites has a promising future as a lightweight and cost-effective microwave absorbing materials for both telecommunication and stealth technology.

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