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Novel a-MWNTs/NH2PAEKK nanocomposite, with a high dielectric constant, low dielectric loss and high breakdown field, were prepared to use a solution blending technique. The uniform dispersion of a-MWNTs in the NH2PAEKK matrix was realized. The dielectric constant of percolating nanocomposites (the a-MWNTs volume fraction of 0.09) was as high as 60 at 103 Hz, it was about 20 times larger than the dielectric constant of NH2PAEKK, and the breakdown field was near 41.4 MV m−1. For fa-MWNTs < fc, the dielectric loss of a-MWNTs/NH2PAEKK nanocomposite was always less than 1. The nanocomposites had tensile strength of 69.2 MPa and tensile modulus of 3.0 GPa. [ABSTRACT FROM PUBLISHER]

Nanocomposites of Sulfonated Poly(Aryl ether ketone) (SPAEK) and functional multiwall carbon nanotubes (a-MWNTs) were fabricated by a solution method. The results showed that the composites exhibited a higher dielectric constant that was near 600 when the volume fraction of carbon-nanotubes was 0.07 (7 vol%) at 103 Hz. The percolation threshold of the a-MWNTs/SPAEK composites was only 3 vol% of a-MWNTs, and the dielectric constant could reach 210. The dielectric constant of composites changed little with frequency increase when the content of carbon nanotubes was more than 3 vol%, and the composites could keep high dielectric constant at high-frequency (>200, at 106 Hz). [ABSTRACT FROM AUTHOR]

Abstract: Pristine carbon nanotubes (CNTs) and noncovalently functionalized carbon nanotubes (f-CNTs) were used to prepare poly(ether ether ketone) (PEEK) composites (CNTs/PEEK and f-CNTs/PEEK) via melt blending. Noncovalently functionalized multiwalled nanotubes were synthesized using hydrogen-bonding interactions between sulfonic groups of sulfonated poly(ether ether ketone) (SPEEK) and carboxylic groups of nanotubes treated by acid (CNTs–COOH). The effects of these two kinds of nanotubes on the mechanical properties and crystallization behavior of PEEK were investigated. CNTs improved mechanical properties and promoted the crystallization rate of PEEK as a result of heterogeneous nucleation. Better enhancement of mechanical properties appeared in the f-CNTs/PEEK composites, which is ascribed to the good interaction between f-CNTs and PEEK. However, the strong interaction of f-CNTs and PEEK chains decreased the crystallization rate of PEEK for high content of f-CNTs. [Copyright &y& Elsevier]

Highlights: [•] Composites filled with mixed fillers showed better properties than those with individual fillers. [•] Improvement in properties was ascribed to synergistic effect of mixed fillers (f-G and f-CNTs). [•] The f-G-f-CNTs(Wf-G/Wf-CNTs =1:1)/PES composite exhibited a percolation threshold of 0.22vol%. [ABSTRACT FROM AUTHOR]