Binary polyamide hybrid composites containing carbon allotropes and metal particles with radiofrequency shielding effect

Abstract

Novel hybrid composites with polyamide 6 (PA6) matrices and binary metal/carbon allotrope reinforcements are synthesized using a two‐stage method. First, activated anionic ring‐opening polymerization (AAROP) of ε‐caprolactam is performed in suspension, in the presence of the desired amounts of different metal particles (Al, Cu, Fe, or Mg) and carbon allotropes (multi‐walled carbon nanotubes or carbon black). The AAROP produces dual core PA6 microcapsules (PAMCs) with controlled shape and size and a total metal/carbon load of up to 17 wt% in respect to the PA6 matrix. Second, these PAMC are compression molded to composite plates. The morphology and the crystalline structure of the different PAMC and their respective composites are studied by electron microscopy and thermal methods. The well‐dispersed binary metal–carbon allotrope fillers in the PA6 matrix increase its electrical conductivity by seven to nine orders of magnitude. Simultaneously, up to ca. 60% increase of the Young's modulus of the hybrids is registered. An almost total disappearance of the PA6 resonance lines in some of the binary hybrids is registered by solid state NMR spectroscopy. The tunable combination of enhanced electrical conductivity and screening of radiofrequencies can be potentially useful in electromagnetic interference shielding or radar absorbing materials. POLYM. COMPOS., 40:E1338–E1352, 2019. © 2018 Society of Plastics Engineers

Tunable Electromagnetic Interference Shielding Properties of Binary Thermoplastic Composites Prepared by Reactive Microencapsulation

“…As seen in Table 1, the conversion of ECL to PA6 is 56% for empty MP and 42−63% for the samples with mono-or binary loads. In accordance with 28,30 this anionic polymerization process leads to the formation of PA6 MP with viscometric molecular weights around 33 kD. It should be noted that both filler types employed do not need any modification for better compatibilization with the matrix PA6.…”

“…The reason why the MP yields are around 50−60% and not closing 98−99% as in the bulk AAROP is related to limited chain propagation due to the crystallization and precipitation of MP when AAROP is carried in solution. 30 The real load RL of the combined metal/ CNT fillers determined by TGA was 2−7% higher than the 10 wt % calculated with respect to the ECL monomer that was fed into the AAROP. Apparently, the RL value will depend on the conversion of ECL to PA6 being higher at lower polymerization yields and vice-versa.…”

“…Such an approach reported previously by Dencheva et al 27 is based on a one-pot solution/ precipitation activated anionic ring-opening polymerization (AAROP) of ε-caprolactam (ECL) in the presence of different fillers, with subsequent transformation of the hybrid PA6 microparticles thus prepared into thermoplastic composite plates by compression molding. A number of composite materials were obtained by this fast and simple method comprising metal, 28 carbonaceous, 29 or mixed 30 loads, being finely dispersed within the thermoplastic PA6 matrix. None of these hybrid composites materials obtained via microencapsulation were ever tried as EMI shields.…”

Magnetically Responsive PA6 Microparticles with Immobilized Laccase Show High Catalytic Efficiency in the Enzymatic Treatment of Catechol

“…Expectedly, no such rods are present in the PA6Fe3O4 support wherein the iron oxide particles are nanosized (80-150 nm). As verified in earlier studies on PA6 magnetic responsive microparticles, most of the magnetic particulate fillers (especially the large Fe particles) are embedded in the core of the respective MP [44].…”

“…The PA6 porous microparticles obtained by AAROP have been extensively studied in previous publications [39,44]. In this work, we will focus only on those characteristics of the laccase-PA6 conjugates that could be related to their catalytic activity.…”