Thermal gasification behavior of plastics with flame retardant

In order to develop effective final treatment system of waste plastics, thermal gasification characteristics of plastics compounds containing flame retardant were investigated. Polypropylene (PP) with flame retardant, which was composed by Al(OH)₃ or (NH₄PO₃)_n, was decomposed in an image furnace. Mass reduction during thermal decomposition was measured by an electric micro-balance. The gas components produced by the thermal decomposition were analyzed with a gas analyzer (MEXA 4000 FT, Horiba Ltd.). Soluble organic fraction (SOF) components in a condensable emission during the decomposition process were analyzed with a combustion type PM analyzer (MEXA 1370 PM, Horiba Ltd.). In addition, SOF and solid carbon in the remains after the thermal decomposition were also analyzed by the PM analyzer. The oxygen concentration was changed from 0% to 21% and the content of flame retardant was changed from 0% to 50%. It was found that thermal decomposition temperature increased with a decrease of oxygen concentration. Flame retardant had small effect on the thermal decomposition temperature. However, gas components produced by thermal decomposition were changed corresponding to the containing ratio of flame retardant. The mass of remains was also affected by the ratio of flame retardant. As for the PP with Al(OH)₃, it was considered that PP was completely decomposed and main component of the remains was Al₂O₃ produced by decomposition of Al(OH)₃ even if the surrounding temperature increased up to 900 K. As for the PP with (NH₄PO₃)_n, gradual mass reductions continued after rapid mass reductions. The ratio of SOF and carbon contents in the remains after decomposition of PP with (NH₄PO₃)_n were higher than the case of PP with Al(OH)₃.     

Influence of doping Mg2+ or Ti4+ captions on the microstructures,thermal radiation and thermal cycling behavior of plasma-sprayed Gd2Zr2O7 coatings

Gadolinium zirconate (Gd₂Zr₂O₇) coatings doped by the transition metal Ti and the alkaline earth metal Mg were expected to have improved thermal radiation performance, which could be combined with their excellent thermal barrier properties to comprehensively improve the thermal insulating performance. The results show that the parent Gd₂Zr₂O₇ powder as well as the Gd-site and Zr-site substituted powders crystallize as pyrochlore Gd₂Zr₂O₇ in Fd-3m space group, while all the as-sprayed coatings have the combination of fluorite and a little part of pyrochlore phase. Gd₂Zr₂O₇ ceramic has high mid-infrared emittance and the addition of Ti⁴⁺ into Gd₂Zr₂O₇ can enhance the infrared absorption/emittance in a specific wavenumber range, dominantly in the near-infrared (0.75–2.5 μm) band due to the enhancement of electron transition induced by the impurity energy levels linked to the widening of the conduction band. The normal spectral infrared emissivity of Gd₂Zr₂O₇-based coating was higher than 0.88 at 1073 K. The monolayered doped Gd₂Zr₂O₇ coatings present very low thermal cycling lifetime, similar with the parent coating, mainly related with their low fracture toughness, despite (Gd_1-xMg_x)₂Zr₂O₇ series display lower thermal conductivity than the parent one.     

Comparative study on thermal shock behavior of thick thermal barrier coatings fabricated with nano-based YSZ suspension and agglomerated particles

Two kinds of segmentation-crack structured YSZ thick thermal barrier coatings (TTBCs) were deposited by suspension plasma spraying (SPS) and atmospheric plasma spraying (APS) with nano-based suspension and agglomerated particles, respectively. The phase composition, microstructure evolution and failure behavior of both TBCs before and after thermal shock tests were systematically investigated. Microstructure of the APS coating exhibits typical segmentation-crack structure in the through-thickness direction, similar with the SPS coating. The densities of segmentation-crack in APS and SPS coatings were about 3 cracks mm⁻¹ and 4 cracks mm⁻¹_, respectively. The microstructure observation also showed that the columnar and equiaxed grains existed in the SPS coating. As for the thermal shock test, the spallation life of the APS TTBCs was 146 cycles, close to that of the SPS TTBCs (166 cycles). Failure of the APS coating is due to the spallation of fringe segments and splats.     

Change in internal energy of thermal diffusion stagnation point Maxwell nanofluid flow along with solar radiation and thermal conductivity

This paper concerns the characteristics of heat and mass transfer in upper convected Maxwell fluid flow over a linear stretching sheet with solar radiation, viscous desperation and temperature based viscosity. After boundary layer approximation, the governing equations are achieved (namely Maxwell, upper convected material derivative, thermal and concentration diffusions). By using the self-similarity transformations the governing PDEs are converted into nonlinear ODEs and solved by RK-4 method in combination with Newton Raphson (shooting technique). The effects of developed parameters on velocity, temperature, concentration, fraction factor, heat and mass diffusions are exemplified through graphs and tabular form and are deliberated in detail. Numerical values of fraction factor, heat and mass transfer rates with several parameters are computed and examined. It is noticed that the temperature is more impactable for higher values of radiative heat transport, thermal conductivity and viscous dissipation. The comparison data for some limiting case are acquired and are originated to be in good agreement with previously published articles.     

Synergistic effect on flame retardancy and thermal behavior of polycarbonate filled with α‐zirconium phosphate@gel‐silica

A new kind of flame retardant (ZS) with layered α‐zirconium phosphate disks (α‐ZrP) as the core and inorganic flame retardant (gel‐silica, GS) to shield solid acid sites on the surface of α‐ZrP as the shell, was synthesized via a facile method. The incorporation effects of ZS with silicone resin on the thermal properties and flame retardance of PC composites were investigated. The presence of ZS could improve the thermal stability of PC matrix. With the addition of ZS contents increased to 3 wt %, the limiting oxygen index (LOI) of the composite was 32.3% and the vertical burning (UL‐94) test reached a V‐0 rating. However, with more contents of ZS, the LOI value decreased, and without the GS layer, the LOI value was decreased significantly as well. The synergism between the α‐ZrP core and gel‐silica shell, also with the silicone resin were found. Based on these results, the flame‐retardant mechanism was proposed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44829.