ABSTRACT
A hyperbranched phosphorus-containing copper phthalocyanine compound (DOPO-CuPc) was successfully synthesized and used as the flame-retardant additive to prepare flame-retarded epoxy thermosets. The addition of DOPO-CuPc led to a significant enhancement of the flame retardant properties of the epoxy resin. The 15DOPO-CuPc/EP composite obtained a LOI value of 35.8%, and the UL-94 rose from NR to V-0 rating. And the addition of DOPO-CuPc resulted in early decomposition of the epoxy thermoset, but the residual char at 700 °C reached 27.7%. The flame retardant mechanism was further investigated. It was found that DOPO-CuPc could release phosphorus-containing radicals and non-combustible gases in the gas phase to exert gas-phase flame retardant activity. In the condensed phase, the epoxy thermoset formed the expanded honeycomb-like char layer during combustion and the presence of copper phthalocyanine contributed to the stability of the char layer.
ABSTRACT
Proton exchange membrane fuel cells (PEMFCs) have received considerable interest due to their low operating temperature and high energy conversion rate. However, their practical implement suffers from significant performance challenge. In particular, proton exchange membrane (PEM) as the core component of PEMFCs, have shown a strong correlation between its properties (e.g., proton conductivity, dimensional stability) and the performance of fuel cells. Metal-organic frameworks (MOFs) as porous inorganic-organic hybrid materials have attracted extensive attention in gas storage, gas separation and reaction catalysis. Recently, the MOFs-modified PEMs have shown outstanding performance, which have great merit in commercial application. This manuscript presents an overview of the recent progress in the modification of PEMs with MOFs, with a special focus on the modification mechanism of MOFs on the properties of composite membranes. The characteristics of different types of MOFs in modified application were summarized.
ABSTRACT
With the increasing emphasis on environmental protection, the development of flame retardants for epoxy resin (EP) has tended to be non-toxic, efficient, multifunctional and systematic. Currently reported flame retardants have been capable of providing flame retardancy, heat resistance and thermal stability to EP. However, many aspects still need to be further improved. This paper reviews the development of EPs in halogen-free flame retardants, focusing on phosphorus flame retardants, carbon-based materials, silicon flame retardants, inorganic nanofillers, and metal-containing compounds. These flame retardants can be used on their own or in combination to achieve the desired results. The effects of these flame retardants on the thermal stability and flame retardancy of EPs were discussed. Despite the great progress on flame retardants for EP in recent years, further improvement of EP is needed to obtain numerous eco-friendly high-performance materials.
ABSTRACT
A one-dimensional photonic crystal elliptical-hole tapered low-index-mode nanobeam cavity sensor fully encapsulated in a water environment is proposed. In the proposed structure, to confine the light in the low-index region and enhance the light-matter interaction, a tapered major axis of the elliptical hole away from the nanobeam cavities center is optimized. Through a three-dimensional finite-difference time-domain simulation, the results show that the low-index-mode of the middle geometry cell is confined in the photonic bandgap of two-sided cells. The highest quality factor of 6.04×105 is achieved when 13 tapered segments and 5 mirror segments are placed at both sides of the host waveguide. The proposed nanobeam structure theoretically possesses a sensitivity of 244.7 nm/RIU (refractive index unit) in a water environment. Moreover, an ultra-compact footprint of 6.4 µm×0.85 µm is achieved, which is only half of the size compared to the best value reported for the nanobeam structure. The results indicate that it is a promising sensor for excellent on-chip sensing with respect to the very small footprint.
