An optimisation approch to determine the electromagnetic properties of lanthanum iron garnet filled PVDF-polymer composite at microwave frequencies

In this study, an optimization approach is shown to improve the accuracy of the Nicholson and Ross Weir (NRW) method to determine both the complex permittivity and permeability of the lanthanum iron garnet-filled PVDF-polymer nanocomposite loaded in a rectangular waveguide. The complex permittivity and permeability values were in turn used in Finite Element Method to calculate the S-parameter and were found to be in good agreement with the measured values

Electron beam irradiation of low density polyethylene/ethylene vinyl acetate filled with metal hydroxides for wire and cable applications

The mechanical test showed that upon irradiation, the tensile strength (TS) values of the EVA/LDPE blends increased with the addition of EVA. A gradual increase in gel content (GC) and tensile strength (TS) with a concomitant decline in elongation at break (EB) and hot set (HS) were observed upon electron beam irradiation of the blends. The densities of all compounds were found to reduce with irradiation. The melt flow index test (MFI) results revealed that addition of ATH and MH reduced the flowability and addition of EVA improved the processability of the LDPE/EVA blend compounds. The TS of the LDPE/EVA blends deteriorated with the addition of flame retardants. The thermal stability and flame behavior of the halogen free flame retarded composites were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and cone calorimeter. The TGA results revealed that the decomposition temperatures of water evolved from the compounds incorporated with MH were significantly higher than that of ATH (i.e. 218–560 °C versus 310–610 °C). The minimum smoke density generation during the combustion obtained with 30% EVA content at both ATH and MH blends. The electrical test showed that the volume resistivity (VR) of the EVA/LDPE blends decreased with increase of EVA, ATH and MH contents, whereas, it declined with increasing irradiation dose. Consequently, this study demonstrated that addition of MH to the irradiated EVA/LDPE blends resulted higher thermal stability, better flammable retardancy, electrical and mechanical properties than addition ATH to the irradiated blends for wire and cable applications

Wpływ zredukowanego tlenku grafenu na właściwości poliamidu 6

Na bazie poliamidu 6 (PA6), przetwarzanego w stanie stopionym z dodatkiem różnej ilości zredukowanego tlenku grafenu (RGO), otrzymano nanokompozyty charakteryzujące się przewodnictwem elektrycznym i termicznym. Nanokompozyty o zawartości 0,5% mas. RGO wykazywały niski próg perkolacji, a próbki o zawartości ~3% mas. GRO – doskonale utworzoną fazę przewodzącą. Badania potwierdziły, że dodatek do PA6 2,0% mas. RGO umożliwił krystalizację struktury PA6, głównie w wyniku przyspieszenia tworzenia się jądra krystalicznego, i osiągnięcie zarówno największych, jak i najmniejszych wymiarów ziaren krystalicznych, co pozwoliło na utworzenie maksymalnie bezbłędnej matrycy krystalicznej. Wyniki dynamicznych testów reologicznych wskazały na niezależność modułu elastyczności (G’) od częstotliwości i na gwałtowne zmniejszenie kąta fazowego w obszarze małej częstotliwości w wypadku próbek nanokompozytów o zawartości RGO 2% mas., typowe dla zmian właściwości reologicznych przy przejściu ze stanu ciekłego do stanu stałego i potwierdzające rozwój struktury połączeń perkolacyjnych PA6 z RGO, pełniącym funkcję czynnika sieciującego. Włączenie do struktury PA6 zredukowanego tlenku grafenu przyczyniło się do polepszenia właściwości ogniochronnych otrzymanych nanokompozytów. Ocena morfologii próbek nanokompozytów wykazała, że cząstki RGO rozproszyły się równomiernie w strukturze PA6. Na podstawie wyników kalorymetrii stożkowej stwierdzono uniepalniający wpływ dodatku RGO do PA6. Wykazano, że opisaną metodą można otrzymywać na skalę masową przewodzące prąd nanokompozyty PA6/RGO.Polyamide 6 (PA6) nanocomposites with electric and thermal conductive properties were formulated via melt processing of PA6 and different inclusion of reduced graphene oxide (RGO). These nanocomposites showed that the small percolation threshold and the perfect formation of conductive link form with 0.5 wt % and ~3.0 wt % of RGO, respectively. Examination of crystallization confirmed that RGO enabled the crystallization of PA6 structure mostly through speeding up the formation of crystal nucleus, reaching the biggest and the smallest of crystal grain extent with RGO inclusion up to 2.0 wt % what enabled the generation of the most unflawed crystalline matrix. Dynamic rheological testing results indicated the frequency-independence of G’ and abruptly decrease phase angle at the small-frequency area via RGO content of 2.0 wt % specifies the alteration state from liquid-state to solid-state rheological performance, and validates the development of percolation link structure with RGO in the function of a crosslinking factor. The progress of fire-retardant characteristics of PA6 was attained due to the inclusion of RGO in the PA6 structure. Morphological research showed that RGO was spread consistently in the PA6 structure. The outcomes of cone calorimetry showed that the flame-retardant characteristics of PA6 were promoted with the addition of RGO in the PA6 structure. These tests show substantial capacity for the bulk manufacture of electric conductive polymer/RGO nanocomposites

Properties of ethylene-vinyl acetate filled with metal hydroxide

In this study, the properties of ethylene-vinyl acetate (EVA) and EVA filled with aluminum (aluminum trihydrate; ATH) and magnesium hydroxide (MH) as halogen-free flame-retardant materials were studied. Scanning electron microscopic analysis revealed that MH in EVA matrix is platy in structure, considerably broad size distribution and well homogeneously distributed, whereas ATH particles are smaller and much more homogeneous in size. Addition of ATH or MH to EVA had an impressive affection on the thermal aging and flame tests but impaired the blend mechanical properties. This research explored that in comparison with ATH, addition of MH to EVA blends was more efficient and suitable in all mechanical, thermal, and flammability tests

Mechanical, electrical, and thermal properties of irradiated low-density polyethylene by electron beam

The effect of electron-beam (EB) irradiation on the mechanical, electrical, and thermal properties of low-density polyethylene (LDPE) was studied The LDPE was irradiated by using 3 MeV EB machine at doses ranging from 25 to 250 kGy in air at room temperature and analyzed for mechanical, thermal, and electrical properties. It was revealed by differential scanning calorimetry analysis that the crystallinity of the EB-radiated LDPE decreased slightly as verified by a marginal reduction in the densities, enthalpy, and melting points. Thermogravimetric analysis test showed that the thermal degradation of LDPE improved by increasing irradiation. The results obtained from both gel content and hot set tests, indicating whether the applicable LDPE has been properly cross-linked or not, showed that under the EB irradiation conditions employed, the cross-linking of the LDPE samples occur mainly in the amorphous region, and the cross-linking density at each irradiation dose depends almost on the amorphous portions of the LDPE. A significant improvement in the tensile strength of the neat LDPE samples was obtained upon EB up to 250 kGy with a concomitant decline in elongation at break. The results on the electrical properties revealed that the surface resistance, volume resistivity, and dielectric strength of the LDPE increase with irradiation dose and reaches a maximum at a 250 kGy irradiation dose. No considerable change of breakdown voltage, dielectric constant, and dielectric loss factor were observed with increasing irradiation dose. The enhancement in the heat deformation, hardness, and thermal aging properties of LDPE upon EB irradiation, suggests that irradiated LDPE is more thermally and mechanically stable than virgin LDP

Mechanical and electrical properties of low density poly ethylene filled with carbon nanotubes

<p>The present research looked into both dependence of CNT content on mechanical and electrical properties in low density polyethylene (LDPE) contain CNT compounds.</p

Electron beam irradiation of LDPE Filled with calcium carbonate and metal hydroxides

This article deals with the effect of electron beam irradiation and flame-retardant loading on the performances of LDPE-based formulations for wire and cable applications. In this study the influence of electron beam irradiation on different blends of low density polyethylene (LDPE) filled with aluminum trihydrate (ATH), magnesium hydroxide (MH), and calcium carbonate (CaCO3) were studied. The mechanical, thermal, and burning properties of the resulting polymer networks have been analyzed and discussed. Addition of all non-halogenated fillers to LDPE deteriorated the mechanical properties. Addition of MH to LDPE presented a significant increase on adhesion forces inside polymer matrices and acted more efficiently than similar ATH/LDPE and CaCO3/LDPE compounds. LDPE flame retardancy improved significantly by a carbonaceous, non-flammable coating formation with high plasticity of CaCO3 addition at high temperature. The resulting MH blends were more efficient thermally and burned more stably than similar ATH blends. It was also concluded that electron beam irradiation had improved effects on thermal stability and mechanical properties for all the polymeric samples in this research