Synthesis of a Novel Phosphorus-Containing Flame Retardant Curing Agent and Its Application in Epoxy Resins.

A novel phosphorus-containing compound diphenyl-(2,5-dihydroxyphenyl)-phosphine oxide defined as DPDHPPO was synthesized and used as flame retardant and curing agent for epoxy resins (EP). The chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, 1H, 13C and 31P nuclear magnetic resonance. The flame retardant properties, combusting performances and thermal degradation behaviors of the cured epoxy resins were investigated by limiting oxygen index (LOI), vertical burning tests (UL-94), cone calorimeter and thermogravimetric analysis (TGA) tests. The morphologies and chemical compositions of char residues for cured epoxy resins were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The water resistant properties were evaluated by putting the samples into distilled water at 70 degrees C for 168 h. The results revealed that the EP/40 wt% DPDHPPO/60 wt% PDA thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 31.9%. The cone tests results revealed that the incorporation of DPDHPPO efficiently reduced the combustion parameters of epoxy resins thermosets, such as heat release rate (HRR), total heat release (THR) and so on. The TGA results indicated that the introduction of DPDHPPO promoted epoxy resins matrix decomposed ahead of time compared with that of pure EP and led to a higher char yield and thermal stability at high temperature. The morphological structures and analysis of XPS of char residues revealed that DPDHPPO benefited to the formation of a sufficient, compact and homogeneous char layer with rich flame retardant elements on the epoxy resins materials surface during combustion. After water resistance tests, EP/40 wt% DPDHPPO/60 wt% PDA thermosets still remained excellent flame retardancy, the moisture absorption of epoxy resins thermosets decreased with the increase of DPDHPPO contents in the thermosets due to the existing of P-C bonds and the rigid aromatic hydrophobic structure.

Construction and mechanism analysis of flame-retardant, energy-storage and transparent bio-based composites based on natural cellulose template.

With the proposal of sustainable development strategy, bio-based energy storage transparent wood (TW) has shown broad application value in green buildings, cold chain transportation, and optoelectronic device fields. However, its application in most fields is limited due to its own flammability. In this study, epoxy resin, triethyl phosphate (TEP) and polyethylene glycol (PEG) were introduced into delignified balsa wood template by vacuum pressure impregnation, and bio-based TW/PEG/TEP integrating flame retardant, high strength and phase-change energy-storage performance was prepared. TW/PEG composites have no leakage during phase change process and their transparency is up to 95 %. Compared with TW/PEG, the shielding effect of char layer and the inhibition effect in condensed and gas phase significantly decrease the total heat release of TW/PEG/TEP. TW/PEG/TEP biocomposites still maintained a high enthalpy of phase change and a low peak melting temperature, which was conducive to its application around the area of low temperature phase change energy storage. In addition, the tensile strength of TW/PEG/TEP was nearly 4 times higher than that of DW, and its toughness was obviously enhanced. TW/PEG/TEP biocomposites conformed to the current concept of energy-saving and green development. It has the potential to replace traditional petrochemical-based materials and shows excellent application prospects in emerging fields.