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