Preparation, Characterization And Flame Retardant And Thermochemical Properties Of Two Calcium Borate Nanomaterials

Calcium borate is an effective and inexpensive inorganic flame retardant,with high thermal stability,non-toxic,suppress smoke,combustion products environment friendly and permanent flame retardant ect.However,the larger calcium borate particles are hardly dispersed in the matrix,which restrains their uses in industry.It was found that the size and the morphology of a fire retardant also greatly affect its flame retardant property.So far,the preparation of calcium borate nanomaterials and investigation of their flame retardant properties are rarely reported.The thermodynamic properties of the same composition calcium borate with different morphologies were less investigated.And the research of calcium borate nanocomposite formed with traditional fire retardant is also rare.Therefore,the investigations of the synthesis,characterization and property of flame retardant about calcium borate nanomaterials and nanocomposites are of very important practical significance.In this paper,calcium borates for 2CaO·B2O₃·H₂O and 2CaO·5B2O₃·5H₂O nanomaterials,and 2CaO B2O₃-H₂O/Mg?OH?2 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 field emission transmission electron microscopy?FTEM?.And their flame retardant properties have also been studied by using thermal analysis method and limited oxygen index method.The thermodynamic parameters were also obtained by calorimetry method.Details are as follows:?1?The 2CaO B2O₃·H₂O nanoflake and nanobelt have been synthesized by hydrothermal method at 180 ? with activated CaO,CaCl₂ and H₃BO₃ as raw materials.The sector-like microstructure has been synthesized under hydrothermal conditions at 120 ? with Ca?NO₃?2·4H₂O and H₃BO₃ as raw materials.The influences of calcium source,boron source,molar ratio,surfactant and complexant,etc.on the morphology and size of calcium borate have also been investigated by many groups of comparison test.?2?Calcium borate 2CaO·5B2O₃·5H₂O nanoplate has been synthesized at 90 ?with CaCl₂ and H₃BO₃ as raw materials and with solution pH value of 7.0.The nanosheet and flower-like nanostructure have been synthesized at 150 ? with solution pH values of 5.5,6.5,respectively.The influences of calcium source,pH value of solution,surfactant and complexant,etc.on the morphology and size of calcium borate of 2CaO·5B2O₃·5H₂O have also been investigated by many groups of comparison test.?3?The 2CaO·B2O₃·H₂O/Mg?OH?2 nanocomposite has been synthesized by in-situ hydrothermal reaction at 180 0C with CaCl₂,H₃BO₃ and new-made Mg?OH?2 nanosheet as raw materials.The influences of experimental method and magnesium source,etc.on the morphology and size of 2CaO·B2O₃·H₂O/Mg?OH?2 nanocomposite have also been investigated by many groups of comparison test.?4?The flame retardant properties of the prepared 2CaO·B2O₃ H₂O,2Ca0·5B2O₃·5H₂0 nanomaterials and 2CaO·B2O₃·H₂O/Mg?OH?2 nanocomposite 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 calcium borate nanocomposite is superior to the single component or their physical mixture.?5?The enthalpies of solution of the synthesized 2CaO·B2O₃·H₂O nanoflake and nanobelt in 1 mol·L-1 HCl?aq?were determined by heat conduction microcalorimeter,respectively.The molar enthalpies of solution of samples with the same constitution but different morphology and size were different because of the surface effect of nanomaterials.With incorporation of the previously determined enthalpies of solution of CaO?s?and H₃BO₃?s?in 1 mol.dm-3 HCl?aq?,and the standard molar enthalpies of formation for CaO?s?,H₃BO₃?s?,and H₂0?1?,the standard molar enthalpies of formation of-?3033.8 ± 2.5?kJ·mol-1 for 2CaO·B2O₃·H₂O nanoflake and-?3036.8 ± 2.6?kJ·mol-1 for 2CaO·B2O₃·H₂O nanobelt were obtained through the designed thermochemical cycle.Comparing with the previous reported standard molar enthalpy of formation of-?3041.8 ± 2.5?kJ mol-1 for bulk 2CaO B2O₃ H₂O sample,it can be found that the standard molar enthalpies of formation increase with the decrease of sizes,which indicates that their thermal stabilities decrease with the decrease of sizes.