Self-Assembly of α-MnO₂ Nanorods into Spheres: Synthesis and Electrochemical Properties

Abstract

Organically-modified montmorillonite (MMT) clays have been prepared using ammonium salts containing quinoline, pyridine, benzene, and styrenic groups. The nanocomposites were prepared by melt blending and the formation of nanocomposites was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability were evaluated by thermogravimetric analysis (TGA) and cone calorimetry measurements, respectively. The presence of modified MMT at 5% loading resulted in significant improvement in thermal stability compared to the virgin polymer. Effective activation energies for mass loss were determined via a model-free isoconversional approach from TGA data obtained under N 2 and under air. The additives served to raise the activation energy, with a more significant impact observed under pyrolysis conditions. The onset temperature of degradation and temperature of maximum decomposition rate are increased, while the peak heat release rate and mass loss rates are significantly reduced in the presence of three of the modified clays. No reduction in the total heat released is observed.

Thermal and flammability study of polystyrene composites containing magnesium–aluminum layered double hydroxide (MgAl–C16 LDH), and an organophosphate

“…The lower initial degradation of composites containing high amounts of organophosphorus compounds has been attributed to the loss, at low temperatures, of low molecular T 0.1 , temperature at which 10 % mass loss occurs and is regarded as the onset of degradation; T 0.5 , temperature at which 50 % mass loss occurs; DT 0.5 difference between T 50 of the composite and pure PS S. Majoni weight compounds from the organophosphorus compound due to weak P-O bonds [19,26,38]. Mass difference curves (difference between mass% of composites and pure PS) for composites have been used to highlight the effects of the additives on the thermal stability of polymers [39]. A positive profile of the mass difference curve indicates that the composites are more stable than the pure polymer at a given temperature and the additive has thus enhanced the thermal stability of the polymer.…”

The effect of boron-containing layered hydroxy salt (LHS) on the thermal stability and degradation kinetics of poly (methyl methacrylate)

“…Isoconversional methods do not suffer from that drawback and enables the determination of the dependency of Ea on the extent of reaction and are therefore favored over model-fitting methods [37], [38] and [39]. Both isothermal and non-isothermal methods have been used in the determination of kinetic parameters in the degradation of polymers [17], [29], [40], [41] and [42].…”

“…The above equation can be rewritten as follows [41]; (3) accessed by following the link in the citation at the bottom of the page.…”

“…For an additive to be effective as a fire retardant, it should be able to break the above cycle. This can be achieved in a variety of ways which include; (i) improvement of thermal stability of the polymer, (ii) dilution and subsequent quenching of the flame, and (iii) providing a barrier for heat and mass transfer [41] ZHTMDBB might act by diluting and quenching the flame by generation of non combustible materials such as CO2 and water from decomposition of the additive. In addition, the char produced during the burning process may act as a barrier to heat and mass transfer reducing the diffusion of combustible products of decomposition, or a combination of the two mechanisms.…”

Flame retardancy materials based on a novel fully end-capped hyperbranched polysiloxane and bismaleimide/diallylbisphenol A resin with simultaneously improved integrated performance

“…Therefore, an effective flame retardant should be able to break the above cycle through following one or more routes: (1) improve the thermal stability of the polymer, (2) dilute and subsequently quench the flame, (3) act in the gas phase and/ or the condensed phase through physical and chemical mechanisms, 38,39 and (4) provide a barrier for heat and mass transfer. 40 As we know, thermo-gravimetric behavior not only determines the service temperature of the material, but also can be used to predict the flame retardancy because the flame retardancy of a polymer is directly related to whether the thermal degradation step proceeds easily or not. Generally, prior to ignition, thermooxidative decomposition results in pyrolysis of fuel and other species; while after ignition, during steady flaming, even in wellventilated conditions, pyrolysis of the condensed phase is essentially anaerobic, with all the oxidation taking place in the gas phase.…”