Surface nanogrooving of carbon microtubes

Extrusion processing of carbon tubes can be problematic due to their poor interfacial interactions with polymeric matrices. Surface chemical modification of carbon tubes can be utilized to create bonding sites to form networks with polymer chains. However, chemical reactions resulting in intermolecular primary bonding limit processability of extrudate, since they cause unstable rheological behaviour, and thus decrease the stock holding time, which is determinative in extrusion. This study presents a method for the synthesis of carbon microtubes with physically modified surface area to improve the filler and matrix interfacial interactions. The key concept is the formation of a nanogrooved topography, through acoustic cavitation on the surface of processing fibres. The effect of nanogrooving on roughness parameters is described, along with the role of surface modified carbon tubes on rheological behaviour, homogeneity, and coherency of extrudate. The measurements showed that nanogrooving increases the surface area of carbon microtubes, as a result, die swelling of the extrudate is reduced. Furthermore, after solidification, the mechanical strength of composite is reinforced due to stronger interactions between nanogrooved carbon tubes and polymer matrix

Preparation and properties of metal-containing polyamide hybrid composites via reactive microencapsulation

Polyamide 6 microcapsules (PAMC) loaded with 2-8 wt% of Cu, Zn or Fe and up to 30 wt% of Al particles are synthesized via activated anionic polymerization (AAP) of ε-caprolactam in suspension performed in the presence of the respective micro- or nanosized loads. The high-molecular weight porous PAMC are with typical diameters of 10-90 μm depending on the size of the metal filler particles. The latter are entrapped in the core of PAMC as proven by microscopy methods. The melt processing of the loaded microcapsules produced PA6/metal hybrid thermoplastic composites with homogeneous distribution of the loads without any functionalization. The crystalline structure of all PAMC and molded composites are studied by thermal and microfocus X-ray diffraction methods suggesting polymorph changes during the transition from PAMC to molded plates. Mechanical tests in tension showed that transforming Al-loaded PAMC into composites produces polyamide hybrids with higher modulus and strength at break. Measuring the conductivity and dielectric properties of the composites in linear and cyclic modes showed that 30 wt% of Al can change significantly the permittivity of the hybrid composites without increasing the conductivity of the PA6 matrix.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) in the frames of the Strategic Project LA25/2013-2014, projects PTDC/EEI-SII/5582/2014 and PTDC/CTMENE/ 5387/2014 and post-doctoral grant SFRH/BPD/45252 co-financed by QREN-POPH program of the EU and of MiNaXS beamline of DESY – Hamburg, Germany. Financial support from the Basque Government Industry Department under the ELKARTEK Program is also acknowledged. SLM thanks the Diputación Foral de Bizkaia for financial support under the Bizkaia Talent program; European Union’s Seventh Framework Programme; Marie Curie Actions – People; Grant agreement nº 267230