| Calcium borate is an effective and inexpensive inorganic flame retardant,with high thermal stability,non-toxic,suppress smoke,environment friendly and permanent flame retardant properties,ect.However,the larger calcium borate particles restrain their uses in industry which are hardly dispersed in the matrix.We found that the morphology and the size of a fire retardant also greatly affect its flame retardant property.If the nano-borate flame retardant combines with other flame retardants as the nanocomposite,it can not only reduce the amount of addition but also significantly increase flame retardant,demonstrating a synergistic flame retardant effect.So far,the preparation and flame retardant properties of calcium borate nanomaterials and nanocomposite are rarely reported.Therefore,the investigations of the synthesis,characterization and of flame retardant about calcium borate nanomaterials and nanocomposites are of very important practical significance.In this paper,calcium borates for 2CaO·3B2O3·H2O and CaO·4B2O3·2H2O nanomaterials,and CaO·4B2O3·2H2O-SiO2 nanocomposite have been prepared under hydrothermal conditions,respectively,which were characterized by X-ray diffraction(XRD),fourier transform infrared spectroscopy(FT-IR),X-ray spectroscopy(EDS),thermogravimetric analysis(TGA),field emission scanning electron microscopy(FESEM)and energy dispersive X-ray spectroscopy(EDX).And their flame retardant properties have also been studied by using thermal analysis method and limited oxygen index method.The mechanical property of polypropylene/nanoborate composite material has also been evaluated.Details are as follows:(1)The 2CaO·3B2O3·H2O nanoribbon have been synthesized by hydrothermal method at 240 ℃ with synthesized K2Ca[B4O5(OH)4]2 8H2O and H3BO3 as raw materials.The bundle nanostructure and fan-shaped micro structure have been synthesized under hydrothermal conditions at 240 ℃ for 12 h and 24 h respectively with Ca(OH)2 and H3BO3 as raw materials.The influences of ultrasound,solution concentration,raw material ratio,surfactant,solution pH,reaction temperature,etc.on the morphology and size of calcium borate have also been investigated under different experimental conditions.(2)Calcium borate CaO·4B2O3·2H2O nanosheet has been synthesized at 170 0C for 10 h with CaCl2 and H3BO3 as raw materials.When the solvent was dimethylformamide,CaO·4B2O3·2H2O nanoleaf was prepared.The non-nanobelt has been synthesized at 170 ℃ for 10 h.The influences of calcium source,solvent type,solvent volume and reaction temperature,etc.on the morphology and size of calcium borate of CaO·4B2O3·2H2O have also been investigated by many groups of comparison test.(3)CaO·4B2O3·2H2O-Si02 nanocomposite has been prepared by in-situ reaction at 170 ℃ with CaCl2,H3BO3 and amorphous silica colloid prepared by the Stober method,in which the SiO2 nanoparticles were attached to the CaO·4B2O3·2H2O nanosheets through the self-assembly process.The contents of the composite sample were measured by thermal analysis and energy dispersive energy dispersive spectroscopy,respectively.The results of the two test methods are consistent.The possible formation mechanism of CaO·4B2O3·2H2O-SiO2 nanocomposites has been proposed.(4)The flame retardant of 2CaO3B2O3·H2O,CaO·4B2O3·2H20 nanomaterials and CaO·4B2O3·2H2O-SiO2 nanocomposite to polypropylene were investigated by the thermal analysis method and limited oxygen index method,including a non-isothermal decomposition kinetic method.Flame retardant experimental results show that the smaller the size of the nano-materials,the more uniform morphology,the better its flame retardancy.The flame retardancy of CaO·4B2O3·2H2O-SiO2 nanocomposite is superior to the single component or their physical mixture CaO·4B2O3·2H2O and SiO2 of the same composition,which shows a good synergistic flame retardant effect.The mechanical properties of CaO·4B2O3·2H2O-SiO2/polypropylene composites were evaluated and the flame retardant mechanism of CaO·4B2O3·2H2O-SiO2 nanocomposites was proposed.In summary,CaO·4B2O3·2H2O-SiO2 can be used as a potential flame retardant for polymer. |
