The flame‐retardant rigid polyurethane foams (RPUFs) with dimethyl methylphosphonate (DMMP) and modified ammonium polyphosphate (MAPP) were prepared. The results showed that the limiting oxygen index (LOI) value was improved by adding DMMP into RPUF/MAPP composite; 10 wt% of DMMP addition can increase the LOI value from 24.3% to 26.0%, where the commercial application standard of RPUF is achieved. Further benefits of using DMMP/MAPP system included restraining of total heat and smoke release, improvement of thermal stability, and char yield of RPUF. The thermogravimetric analysis (TGA)‐gas chromatography‐mass spectrometer (GC‐MS) results indicated that DMMP/MAPP could continuously release PO2 and PO·free radicals in the gas phase. In addition, DMMP/MAPP exhibited the charring effect and barrier effect in the condensed phase, such bi‐flame retardant effect exerted by DMMP/MAPP resulted in the enhanced flame retardant property of RPUF.
A series of flame‐retardant polycarbonate (PC) composites with different ratios of phosphazene‐triazine bi‐group flame retardant (A3) were prepared. The flame retardant performance and thermal stability of PC/A3 composites were characterized by LOI, UL 94 vertical burning test, cone calorimetry test and TG. Results show that when the addition of A3 is 13.5%, the PC/A3 composite can pass UL94 V‐0 level with a LOI value of 29.3% and reduce the peak heat release rate by 47.5% during the combustion. TG results show that adding 5% A3 can increase the initial decomposition temperature of the PC by 7°C in nitrogen and 9°C in air. Investigation of the morphology and chemical structure of char residue demonstrates that A3 promotes the formation of more complete and compact char residue which acts as physical barriers to inhibit the transfer of heat and oxygen, resulting the good flame retardant properties. The analysis of gaseous pyrolysis product reveals that A3 also exerts a flame‐retardant effect in gas phase by releasing PO· free radicals.
The flame-retardant rigid polyurethane foams (RPUF) were prepared by using modified ammonium polyphosphate (MAPP) combined with expandable graphite (EG) and dimethyl methylphosphonate (DMMP). The thermal stability, flame retardant property, and mechanical property of flame-retardant RPUF were evaluated based on thermogravimetric analysis (TGA), limiting oxygen index (LOI) test, cone calorimetry tests, scanning electron microscopy (SEM) and compressive strength tests. The results showed that an efficient ternary flame retardant system, DMMP/EG/MAPP, for rigid polyurethane foam was constructed. When the ratio of DMMP/EG/MAPP was 4/12/4, the cell size of RPUF composite was the most homogeneous, and the LOI value of RPUF composite reached 31.9%. The peak heat release and total smoke release value decreased to 97 kW/m 2 and 347 m 2 /m 2 , respectively. The RPUF composites with 4%DMMP/12%EG/4%MAPP exhibited the best flame retardant property because DMMP/EG/MAPP played great free radical quenching effect in the gas phase by releasing the POÁ and PO 2 Á free radicals during the whole combustion process. Meanwhile, the compact char layer with "connected worm-like" structure exerted barrier effect in the condensed phase.
A novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano ZnO (A4‐d‐ZnO) was synthesized and applied in poly (lactic acid) (PLA). Fourier transform infrared (FTIR), solid state nuclear magnetic resonance (SSNMR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS) were used to confirm the chemical structure of A4‐d‐ZnO. The thermal stability and the flame‐retardant properties of the PLA composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI), vertical burning test (UL‐94), and micro combustion calorimeter (MCC) test. The results of XPS showed that A4‐d‐ZnO has been synthesized, and the doping ratio of ZnO was 7.2% in flame‐retardant A4‐d‐ZnO. TGA results revealed that A4‐d‐ZnO had good char forming ability (40 wt% at 600°C). The results of LOI, vertical burning test, and MCC showed that PLA/5%A4‐d‐ZnO composite acquired a higher LOI value (24%), higher UL94 rating, and lower pk‐HRR (501 kW/m2) comparing with that of pure PLA. It indicated that a small amount of flame‐retardant A4‐d‐ZnO could achieve great flame‐retardant performance in PLA composites. The catalytic chain scission effect of A4‐d‐ZnO could make PLA composites drip with flame and go out during combustion, which was the reason for the good flame‐retardant property. Moreover, after the addition of A4‐d‐ZnO, the impaired mechanical properties of PLA composites are minimal enough.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.