Preparation Of Nickel Hydroxystannate And Study On Its Flame Retardant Epoxy Resin

Epoxy resin（EP）is widely used in civil construction,aerospace,and automotive machinery because of its excellent processability,chemical resistance,and electrical insulation properties.However,due to the low fire safety,the application of EP in various fields is largely restricted;and once a combustion occurs,the EP material itself will release a large amount of polluting gases and smoke,which will harm people’s healthy.Therefore,in order to reduce the fire hazard of EP materials,flame retardant research of EP is urgent.In this paper,Nickel hydroxystannate（NiSn（OH）₆,NHS）flame retardant was prepared and applied to EP to reduce the fire risk of EP matrix.The effects of NHS on the flame retardancy and mechanical properties of EP matrix were studied by limit oxygen index（LOI）,Cone calorimeter（Cone）and tensile testing machine.The flame retardancy mechanism of flame retardant EP samples during combustion was analyzed by means of thermogravimetric analysis（TGA）,cone and X-ray photoelectron spectroscopy（XPS）,the details are as follows:In the first part,the amorphous,spherical and cubic NiSn（OH）₆ flame retardants with the best morphology were successfully prepared by co precipitation method through adjusting the reactant concentration,molar ratio,and ammonia water content,surfactant and reaction temperature during the experiment,which were A-NHS,S-NHS and C-NHS.The materials were characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,TGA and Fourier transform infrared spectrometer（FTIR）.The results showed that the products of the three morphologies are pure NiSn（OH）₆.The particle size of A-NHS is about 150 nm with serious agglomeration;The particle size of S-NHS is about 120 nm microsphere with good dispersion;The particle size of C-NHS is about 130 nm cube with good dispersion.In addition,the initial decomposition temperature(T_5%)of the three samples is higher than the processing temperature of EP samples,which meets the necessary conditions for processing.The second part is the study of NHS flame retardant EP.The flame retardant and mechanical properties of EP/NHS samples were studied by LOI,Cone,TGA and tensile testing machine.The results showed that the LOI level of flame retardant EP samples increased by 3.4-8.2 units with different proportion of A-NHS,S-NHS and C-NHS added to EP matrix,and the mechanical properties of EP/S-NHS samples were significantly better than those of EP/A-NHS and EP/C-NHS samples.The LOI level of EP/5S-NHS was 6.8 units higher than that of pure EP,but the tensile strength was only 4.8%lower.To sum up,EP sample has the best comprehensive performance when adding 5 parts of S-NHS flame retardant separately;the Cone calorimetric results showed that the addition of NHS could effectively reduce the heat release rate and smoke density of the materials;however,all NHS flame retardant EP samples are of no grade in UL-94 vertical combustion test.In the third part,the flame retardant EP of NHS synergistic ammonium polyphosphate（APP）was studied.In order to make the flame retardant EP sample pass the V-0 level of UL-94 vertical combustion test,the synergistic effect of APP and NHS in EP was studied.The results showed that EP/6APP could pass through V-1 level of UL-94.When 0.1 and 0.5 NHS were used to replace APP respectively,except EP/5.5APP/0.5A-NHS,all EP/5.9APP/0.1NHS and EP/5.9APP/0.5NHS samples can pass through V-0 level of UL-94.In addition,there was a synergistic effect between APP and NHS in EP matrix,which could catalyze the rapid formation of carbon in EP matrix,and effectively reduce the heat release rate,smoke release rate,CO release rate,etc.In the process of combustion,S-NHS could catalyze the degradation of APP to generate rich and stable C-N,C-N-P and O=P-O-C structures,which increased the stability of carbon residue;meanwhile,SnO,SnO₂,Ni₂O₃ and NiO could cover the surface of the substrate and play a role of physical barrier.