Barrier, mechanical and conductive properties of polycaprolactam nanocomposites containing carbon-based particles: Effect of the kind of particle

Enhanced Mechanical Property of Polyamide-6/Graphite Sheet Composites with Segregated 3D Network Binary Structure for High Thermal Conductivity

Segregated conductive polymer composites exhibit excellent electrical properties with a low percolation threshold. However, the mechanical properties of the segregated conductive polymer composites were always poor because the conductive fillers at the interfaces hinder polymer chain diffusion and thus lead to weak interfacial interaction between the conductive fillers and the polymer matrix. In this paper, polyamide-6 and polyamide-612 microspheres were synthesized via the in situ anionic ring opening of caprolactam and laurolactam. Segregated graphite sheets/polyamide-6(GS/PA6) and polyamide-612(PA612) composites with good mechanical properties were realized via high-pressure solid-phase compression molding. The microstructures of the composite samples were observed by scanning electron microscopy, which showed that the formation of a GS-conductive network at the PA6 granule interfaces in the segregated conductive structures and the adopting of PA612 considerably improved the interfacial adhesion of the composites. A superior impact strength of 5.1 kJ/m2 was achieved with 50 wt% PA612 loading owing to improvements in the interface compatibility between PA6 and GS. The composites possessed an ultralow percolation threshold, which was ascribed to the segregated network structure being successfully constructed inside the material. As for GS/PA6 composites, the combination of segregated GS-conductive networks achieved an ultralow percolation of 2.8 vol%. The percolation of 80PA6/20PA612-GS composites was slightly higher, measuring up to 3.2 vol%. Moreover, the thermal conductivity of the 80PA6/20PA612-GS composites increased from 0.26 to around 0.5 W/(m·K), which was 1.9 times larger than the pure polyamide.

Study of the Influence of Magnetite Nanoparticles Supported on Thermally Reduced Graphene Oxide as Filler on the Mechanical and Magnetic Properties of Polypropylene and Polylactic Acid Nanocomposites

A study addressed to develop new recyclable and/or biodegradable magnetic polymeric materials is reported. The selected matrices were polypropylene (PP) and poly (lactic acid) (PLA). As known, PP corresponds to a non-polar homo-chain polymer and a commodity, while PLA is a biodegradable polar hetero-chain polymer. To obtain the magnetic nanocomposites, magnetite supported on thermally reduced graphene oxide (TrGO:Fe₃O₄ nanomaterial) to these polymer matrices was added. The TrGO:Fe₃O₄ nanomaterials were obtained by a co-precipitation method using two types of TrGO obtained by the reduction at 600 °C and 1000 °C of graphite oxide. Two ratios of 2.5:1 and 9.6:1 of the magnetite precursor (FeCl₃) and TrGO were used to produce these nanomaterials. Consequently, four types of nanomaterials were obtained and characterized. Nanocomposites were obtained using these nanomaterials as filler by melt mixer method in polypropylene (PP) or polylactic acid (PLA) matrix, the filler contents were 3, 5, and 7 wt.%. Results showed that TrGO₆₀₀-based nanomaterials presented higher coercivity (Hc = 8.5 Oe) at 9.6:1 ratio than TrGO₁₀₀₀-based nanomaterials (Hc = 4.2 Oe). PLA and PP nanocomposites containing 7 wt.% of filler presented coercivity of 3.7 and 5.3 Oe, respectively. Theoretical models were used to analyze some relevant experimental results of the nanocomposites such as mechanical and magnetic properties.

Enhanced gas barrier properties of polymer substrates for flexible OLEDs by adjusting the backbone rigidity and incorporating 2D nanosheets

Ultra-high T_g, low CTE and great ductility as well as a high barrier performance are embodied in PI nanocomposite films.

Barrier Properties of GnP-PA-Extruded Films

It is generally known that significant improvements in the properties of nanocomposites can be achieved with graphene types currently commercially available. However, so far this is only possible on a laboratory scale. Thus, the aim of this study was to transfer results from laboratory scale experiments to industrial processes. Therefore, nanocomposites based on polyamide (PA) and graphene nanoplatelets (GnP) were prepared in order to produce membranes with improved gas barrier properties, which are characterized by reduced permeation rates of helium. First, nanocomposites were prepared with different amounts of commercial availably graphene nanoplatelets using a semi-industrial-scale compounder. Subsequently, films were produced by compression molding at different temperatures, as well as by flat film extrusion. The extruded films were annealed at different temperatures and durations. In order to investigate the effect of thermal treatment on barrier properties in correlation to thermal, structural, and morphological properties, the films were characterized by differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), optical microscopy (OM), transmission electron microscopy (TEM), melt rheology measurements, and permeation measurements. In addition to structural characterization, mechanical properties were investigated. The results demonstrate that the permeation rate is strongly influenced by the processing conditions and the filler content. If the filler content is increased, the permeation rate is reduced. The annealing process can further enhance this effect.

Synthesis and characterization of novel donor–acceptor type neutral green electrochromic polymers containing an indolo[3,2-b]carbazole donor and diketopyrrolopyrrole acceptor

Indolocarbazole bearing donor–acceptor type polymers have rarely been reported in the electrochromic field despite them having considerable development in the applications of organic photoelectric devices. In this paper, two novel soluble electrochromic polymers, namely PDTCZ-1 and PDTCZ-2, were prepared by chemical polymerization including indolo[3,2-b]carbazole (IC) units as the donor, diketopyrrolopyrrole (DPP) units as the acceptor and bithiophene units as the bridging group. Through diverse characterization techniques such as cyclic voltammetry (CV), scanning electron microscopy (SEM), UV-vis spectroscopy and thermogravimetric analysis (TGA), it was found that PDTCZ-1 and PDTCZ-2 exhibited saturated green in the neutral state and pale green in the oxidized state with optical band gaps of 1.44 eV and 1.39 eV, respectively, as well as demonstrating fast switching speed, satisfactory coloration efficiency and favorable thermal stability. In addition, the proportion of donors to acceptors definitely exerted an influence on the electrochromic properties of the polymers. As the thiophene/IC/DPP ratio changed from 4/3/1 (PDTCZ-1) to 5/4/1 (PDTCZ-2), meaning an increase of the donor ratio, the polymer showed a reduced onset oxidation potential, decreased optical band gap and different dynamic parameters. The positive results suggest that PDTCZ-1 and PDTCZ-2 could be promising candidates as neutral green electrochromic materials and deserve more attention and penetrating research.

Two novel neutral green D–A type conjugated polymers were synthesized, illustrating satisfactory electrochromic properties, such as low band gaps, desirable color switches, excellent solubility and favorable thermal stability.