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The goal of this work was the synthesis of novel flame-retarded polyurethane rigid foam with a high percentage of castor oil phosphate flame-retarded polyol (COFPL) derived from renewable castor oil. Rigid flame-retarded polyurethane foams (PUFs) filled with expandable graphite (EG) and diethyl phosphate (TEP) were fabricated by cast molding. Castor oil phosphate flame-retarded polyol was derived by glycerolysis castor oil (GCO), H2O2, diethyl phosphate and catalyst via a three-step synthesis. Mechanical property, morphological characterization, limiting oxygen index (LOI) and thermostability analysis of PUFs were assessed by universal tester, scanning electron microscopy (SEM), oxygen index testing apparatus, cone calorimeter and thermogravimetric analysis (TGA). It has been shown that although the content of P element is only about 3%, the fire retardant incorporated in the castor oil molecule chain increased thermal stability and LOI value of polyurethane foam can reach to 24.3% without any other flame retardant. An increase in flame retardant was accompanied by an increase in EG, TEP and the cooperation of the two. Polyurethane foams synthesized from castor oil phosphate flame-retarded polyol showed higher flame retardancy than that synthesized from GCO. The EG, in addition to the castor oil phosphate, provided excellent flame retardancy. This castor oil phosphate flame-retarded polyol with diethyl phosphate as plasticizer avoided foam destroy by EG, thus improving the mechanical properties. The flame retardancy determined with two different flame-retarded systems COFPL/EG and EG/COFPL/TEP flame-retarded systems revealed increased flame retardancy in polyurethane foams, indicating EG/COFPL or EG/COFPL/TEP systems have a synergistic effect as a common flame retardant in castor oil-based PUFs. This EG/COFPL PUF exhibited a large reduction of peak of heat release rate (PHRR) compared to EG/GCO PUF. The SEM results showed that the incorporation of COFPL and EG allowed the formation of a cohesive and dense char layer, which inhibited the transfer of heat and combustible gas and thus increased the thermal stability of PUF. The enhancement in flame retardancy will expand the application range of COFPL-based polyurethane foam materials. 相似文献
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Study of the recast layer of a surface machined by sinking electrical discharge machining using water-in-oil emulsion as dielectric 总被引:1,自引:0,他引:1
Electrical discharge machining (EDM) caused a recast layer to form at the machined surface of the workpiece. The characteristics of the recast layer have a great relationship with the type of dielectric. The research work in this paper aims to acquire a profound knowledge of the recast layers of a surface machined by sinking EDM using water-in-oil (W/O) emulsion as dielectric. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and micro hardness analysis were performed. The characteristics of the recast layer formed in W/O emulsion were investigated by comparing them with those of the recast layer formed in kerosene and de-ionized water dielectric. It was found that the recast layer formed in W/O emulsion exhibited larger surface roughness, thickness and micro hardness compared with that formed in kerosene and de-ionized water. Both carbide and oxide were detected in the recast layer formed in W/O emulsion whereas only carbide was detected in the recast layer formed in kerosene. Due to the higher supersaturation of gases in the melted material, the recast layer formed in W/O emulsion was found to possess more micro-voids than that formed in kerosene and de-ionized water. 相似文献
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