To address the ever-increasing electromagnetic interference (EMI) pollution, a hybrid filler approach for novel composites was chosen, with a focus on EMI absorbance. Carbon nanofiller loading was limited to 0.6 vol.% in order to create a sustainable and affordable solution. Multiwall carbon nanotubes (MWCNT) and iron oxide (Fe₃O₄) nanoparticles were mixed in nine ratios from 0.1 to 0.6 vol.% and 8.0 to 12.0 vol.%, respectively. With the addition of surfactant, excellent particle dispersion was achieved (examined with SEM micrographs) in a bio-based and biodegradable poly(butylene succinate) (PBS) matrix. Hybrid design synergy was assessed for EMI shielding using dielectric spectroscopy in the microwave region and transmittance in the terahertz range. The shielding effectiveness (20–52 dB) was dominated by very high absorption at 30 GHz, while in the 0.1 to 1.0 THz range, transmittance was reduced by up to 6 orders of magnitude. Frequency-independent AC electrical conductivity (from 10⁻² to 10⁷ Hz) was reached upon adding 0.6 vol.% MWCNT and 10 vol.% Fe₃O₄, with a value of around 3.1 × 10⁻² S/m. Electrical and thermal conductivity were mainly affected by the content of MWCNT filler. The thermal conductivity scaled with the filler content and reached the highest value of 0.309 W/(mK) at 25 °C with the loading of 0.6 vol.% MWCNT and 12 vol.% Fe₃O₄. The surface resistivity showed an incremental decrease with an increase in MWCNT loading and was almost unaffected by an increase in iron oxide loading. Thermal conductivity was almost independent of temperature in the measured range of 25 to 45 °C. The nanocomposites serve as biodegradable alternatives to commodity plastic-based materials and are promising in the field of electromagnetic applications, especially for EMI shielding.

Electrostatic dissipative (ESD), anti-static (AS), and electromagnetic interference (EMI) shielding materials are commonly based on commodity fossil-fuel-based plastics. This, in turn, contributes to ever-growing non-biodegradable plastic pollution. Graphene nanoplatelets (GN), multi-walled carbon nanotubes (MWCNT), nanostructured carbon black (NCB), and amorphous carbon black (CB) were utilized as nanofillers to prepare bio-based and biodegradable poly(butylene succinate-co-adipate) (PBSA) nanocomposites. Solvent-cast composites were prepared with 1.1 to 30.0 vol.% nanoparticle loading. The literature mainly focuses on relatively low loadings; therefore, for this research, filler loadings were increased up to 30 vol.% but the maximum loading for NCB and CB loadings only reached 17.4 vol.% due to a lack of dimensional stability at higher loadings. The composites were characterized using tensile testing, volumetric and surface conductivity measurements, thermal conductivity measurements, dielectric spectroscopy in the microwave region, and transmittance in the terahertz range. Tensile tests showed excellent carbon filler compatibility and enhanced tensile strength for loadings up to 5 vol.% (up to 20 vol.% for MWCNT). The highest thermal conductivity values were reached for the MWCNT filler, with the 30.0 vol.% filled composite reaching 0.756 W/mK (262% increase over PBSA). All fillers were able to produce composites that yielded volume conductivities above 10⁻¹⁰ S/m. Composites with MWCNT, GN, and NCB inclusions above the percolation threshold are suitable for EMI applications in the microwave and THz frequency range.

This study examines how various nanofillers impact thermal conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding potential of bio-based and biodegradable poly(butylene succinate-co-adipate) (PBSA). TiO₂, NiFe₂O₄, Fe₂O₃, and Fe₃O₄ were selected as fillers for nanocomposites at 4–50 vol.% (12–81 wt.%). The nanocomposites were analyzed in three domains: structural (scanning electron microscopy, energy dispersive X-ray spectroscopy mapping, density, tensile testing), thermal (light flash analysis, literature models), and dielectric (AC conductivity, permittivity, EM shielding effectiveness (SE)). The investigated fillers showed good dispersion and compatibility with the PBSA matrix. LFA was analyzed according to literature models, where Bruggeman and Agari models showed the best fit at high concentrations. The dielectric analysis revealed that most of the nanocomposites did not reach percolation; thus, producing thermally conductive plastics that are electrically insulating. EMI shielding was limited to frequencies below 10 Hz, with the notable exception of Fe₃O₄ (100 nm and loading of > 25 vol.%), which showed shielding at frequencies up to 10⁵ Hz. The investigated composites based on a biodegradable polyester and abundant metal oxide nanofillers are suitable for the production of cheap, ecological, and electrically insulating heat dissipation solutions required for modern and lightweight applications.

Cellulose surface chemistry controls the Seebeck coefficient of SWCNT buckypaper composites independently of filler loading, enabling partial replacement of the conductive phase without loss of thermoelectric performance. Microfibrillated cellulose was covalently functionalized with citric acid (Cell-CA), 3-trimethoxysilylpropyl methacrylate (Cell-TMSPMA), and 4,4’-diphenylmethane diisocyanate (Cell-MDI), and physically modified with polyethylene glycol (Cell-PEG), then combined with single-wall carbon nanotubes (SWCNTs) at 0.1 to 90 wt% loading. Cell-MDI composites achieved power factors of 101 to 111 µW m ^− 1 K ^− 2 at 70 to 90 wt% SWCNT, matching pure SWCNT buckypaper (106 µW m ^− 1 K ^− 2 ) despite 10 to 30 wt% of the conductive phase being replaced by cellulose. The Cell-MDI Seebeck coefficient remained at 46 to 52 µV K ^− 1 from 10 to 90 wt% SWCNT regardless of loading, while neat cellulose composites ranged from 23 to 45 µV K ^− 1 with no trend. Solvent-exchange controls confirmed that this stability originates from the covalent urethane functionalization; vacuum drying further increased the Seebeck coefficient to 70.4 µV K ^− 1 at 1 wt% SWCNT. Cell-CA reached the highest conductivity (62 kS m ^− 1 ) with lower Seebeck coefficients (19 to 30 µV K ^− 1 ) consistent with additional p-doping; Cell-TMSPMA showed no electronic effect, consistent with phase separation; Cell-PEG achieved N-type conversion (− 27 µV K ^− 1 at 60 wt%) with decreased conductivity. Composites above the percolation threshold provided electromagnetic shielding effectiveness up to 30 dB across 8 to 37 GHz. A proof-of-concept 8-couple Cell-MDI/Cell-PEG module delivered an open-circuit voltage of 10 mV across a ~ 30 K gradient, demonstrating thermoelectric harvesting in a thin-film format.

Fused granulate fabrication expands the printable composition window for electroactive PBAT/PLA/MWCNT nanocomposites, enabling conductive, shape-memory structures that undergo rapid electrically triggered recovery through Joule heating.