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

A new approach for preparation of metal-containing polyamide/carbon textile laminate composites with tunable electrical conductivity

Multiscale thermoplastic laminate composites based on polyamide 6 (PA6) dually reinforced by carbon fiber woven textile structures (CFT) and different micron-sized metal particles are prepared for the first time by microencapsulation strategy. In a first step, activated anionic ring-opening polymerization (AAROP) of epsilon-caprolactam is carried out in suspension, in the presence of different metal particles, to produce shell-core PA6 microcapsules (PAMC) loaded with 13-19% metal. In a second step, the loaded PAMC are distributed between CFT plies with fiber volume fractions V (f) = 0.25 or V (f) = 0.50 and then the ply arrays are consolidated by compression molding. Separately, metal-loaded PA6 hybrid composites are prepared by direct compression molding of PAMC and used to compare their properties to the CFT-metal laminates. Light- and scanning electron microscopy are used to study the morphology and the interfaces between the fillers and the polymeric matrix. These structural results are related to the mechanical behavior in tension and the electrical properties. A notable increase of the d.c. electrical conductivity in 7 orders of magnitude is observed for the CFT-metal laminates with respect to the neat PA6. This increase is accompanied by a 2.5-3.0 times growth of the Young's modulus and of the strength at break. It is concluded that the microencapsulation strategy can be applied to produce multifunctional CFT-metal-PA6 thermoplastic composites with tailored electrical and improved mechanical properties for advanced applications.The authors gratefully acknowledge the financial support of the project TSSiPRO NORTE-01-0145-FEDER-000015, supported by the regional operation program NORTE2020, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund, as well as funding from FCT-Portuguese Foundation for Science and Technology within the strategic projects UID/CTM/50025/2013, LA25/2013-2014 and UID/FIS/04650/2013. FMO acknowledges also the PhD grant PD/BD/114372/2016 of FCT-Portugal (AdvaMTech-PhD Program in Advanced Materials and Processing) and PM the FCT SFRH/BPD/96227/2013 grant. Finally, ZZD is thankful to FCT for the SFRH/BSAB/130271/2017 personal research grant. Finally, SLM acknowledges funding from the Basque Government Industry Department under the ELKARTEK program.info:eu-repo/semantics/publishedVersio