Thermal and dielectric properties of bio-composites containing multi wall carbon nanotubes

Recently, environmental concerns have ever more driven the interest of academic and industrials researchers toward the improvement of functional properties of commercially available biopolymers. In this frame, this work was dedicated to enhance dielectric behavior of a commercial biodegradable blend constituted by two semicrystalline co-polymers, poly(hydroxyl butyrate-co-valerate) (PHBV) and poly(butylenes adipate-co-terephthalate) (PBAT) with a weight ratio 30/70, respectively. At this purpose, bio-composites including different contents, up to 1.2 vol%, of multi wall carbon nanotubes (MWCNTs) with various aspect ratios equal to 30, 105 and 667, were prepared by melt compounding and characterized mainly in terms of thermal and dielectric properties. Results showed that the inclusion of carbon nanotubes influences the thermal properties of PHBV phase with filler aspect ratios and contents primarily affecting crystallization kinetics and mechanisms, respectively. Alterations of the matrix crystallization contribute to the enhancement of typical interfacial polarization phenomena with effects mainly manifested at low frequencies. The aspect ratio of carbon nanotubes strongly influences the electrical properties of composites. High values of enable electrical percolation of composites at very low filler content; low frequency permittivity increases remarkably with MWCNT concentration in proximity of the percolation threshold; a maximum in dielectric losses can be found at a specific frequency and at a specific combination of filler content and aspect ratio.