Impact of halogen-free flame retardant with varied phosphorus´s chemical surrounding on the properties of diglycidyl ether of bisphenol-A type epoxy resin: synthesis, fire behaviour, flame-retardant mechanism and mechanical properties

This work aimed to investigate the effect of two types of phosphorus-containing flame retardants (P-FRs) with different chemical surroundings (phenylphosphonate-based (PO?Ph) and phenylphosphoric-based (PO?OPh)) on the flame-retardant efficiency for diglycidyl ester of bisphenol-A type epoxy (EP) resin. The two series of P-FRs which were named as FPx and FPOx (x = 1, 2 and 3), respectively, showed reactivity with epoxy group that was examined by differential scanning calorimetry (DSC) and variable temperature FTIR spectroscopy (VT-FTIR). A comparative study between the FPx and FPOx (x = 1, 2 and 3) containing flame-retardant epoxy was carried out via investigating their flammability, thermal stability and mechanical properties. The most significant difference in flame retardancy between them was that FPx (x = 1, 2 and 3) endowed EP with a V-0 rating in UL 94 test at 5 wt% loading, while FPOx (x = 1, 2 and 3) showed no rating at such loading. Importantly, it is found that there was almost 10 times difference in the flame-retardant efficiency for EP between FPx and FPOx, though they had similar chemically molecular structures. Moreover, TGA-FTIR and TGA-MS coupling techniques (TGA, thermogravimetric analysis; MS, mass spectroscopy) were employed to study the thermal decomposition of FP1 and FPO1; the impacts of FP1 and FPO1 on the thermal decomposition of EP were studied by TGA-FTIR as well. Furthermore, an online temperature detection experiment was designed to collect the temperatures by thermocouples and infrared thermometers in the UL 94 test. Based on the above results, the flame-retardant mechanisms of FP1 and FPO1 in EP are discussed. In addition, the impact of P-FRs on mechanical properties of EP was studied by means of tensile test and dynamic mechanical analysis

Ferrocene-Based Nonphosphorus Copolymer: Synthesis, High-Charring Mechanism, and Its Application in Fire Retardant Epoxy Resin

A novel nonphosphorus copolymer poly((3,3′-diphenyl diacetylethylenediamino)-1,1′-ferrocene) (PDPFDE) was synthesized, with the aim of reducing the fire hazards of epoxy resin (EP), via an aza-Michael addition reaction and was well characterized. A high char yield of about 62.9 wt % was obtained for PDPFDE from thermogravimetric analysis results, and a charring mechanism has been suggested that involves iron-cored carbon nanotubes as catalysts. An EP composite containing 5.0 wt % PDPFDE reached a low limiting oxygen index value of 29.1% and V-1 rating in the UL-94 test. On comparison with neat EP, the peak of the heat release rate and the total smoke production of the composite were reduced by 36.0% and 24.0%, respectively. Scanning electron microscopy and energy dispersive X-ray analysis results indicated the formation of coherent, dense, and nitrogen-rich char residues due to the incorporation of PDPFDE. Furthermore, the addition of an appropriate amount of PDPFDE improved the mechanical properties compared to pure EP

Effect of Cu-doped graphene on the flammability and thermal properties of epoxy composites

Cu-doped graphene (graphenit-Cu) was successfully prepared through chemical reduction method, and its surface morphology, crystalline structure and Cu content in graphenit-Cu were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductive couple plasma (ICP) and electrochemical cyclic voltammetry, respectively. Graphenit-ox/epoxy systems and graphenit-Cu/epoxy systems were prepared, and the contents of graphenit-ox and graphenit-Cu were kept as 1 and 3 wt%, respectively. The effect of graphenit-ox or graphenit-Cu on the flame retardancy, combustion properties, thermal degradation and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Compared to graphenit-ox, the addition of graphenit-Cu reduced the heat release rate (HRR), total smoke production (TSP) and smoke production rate (SPR), and improved LOI values of epoxy composites. Moreover, the addition of graphenit-ox also had little flame retardant effect on epoxy composite. The possible synergistic effect between graphene and Cu was confirmed in the flame retardant epoxy composites. TGA and DMA results also indicated the considerable effect on the thermal degradation and thermomechanical properties of epoxy composites with the addition of graphenit-Cu. The results supplied an effective solution for developing excellent flame retardant epoxy composites.The authors acknowledged the financial support of China Scholarship Council (CSC: 201308420380), National Natural Science Foundation of China (Grant No. U1201243) and the European Union's Seventh Framework Program for Research, Technological Development and Demonstration (607793). This research is also partly supported by Spanish Ministry of Economy and Competitiveness (MINECO) under Ramón y Cajal grant (RYC-2012-10737).Peer reviewe