Synthesis And Application Of Halogen-Free Flame Retardant Dawsonite And Melamine Phosphate

The tendency to eliminate halogen-based substances to reduce smoke toxicity during combustion has promoted research on halogen-free flame retardant(HFFR).Different HFFR should be used because of the properties of polymer materials are diversity.The use of metal hydroxides,i.e.aluminium hydroxide(ATH) or magnesium hydroxide(MH) has drawn tremendous attention due to their smoke-suppression,low-toxicity and low cost.Halogen-free intumescent flame retardants especially the melamine salts as alternative materials have gained considerable attention because they provide fire protection with minimum of overall health hazard and prefect compatibility.In this thesis,a novel dawsonite flame retardant whiskers was prepared by hydrothermal method and melamine phosphate was successfully synthesized by simple craft.The main research works have been done as follows:(1)NaAl(OH)₂CO₃ whiskers were synthesized by hydrothermal method using aluminium isopropoxide which was prepared in lab freshly and NaHCO₃.The crystalline structure, morphology and thermal stability of synthesized samples were characterized by XRD,SEM, FTIR and TG-DTG.The results indicate that the NaAl(OH)₂CO₃ whiskers possess particle length of 10～20μm,aspect ratio(length to diameter) of 20～40 respectively,and good distribution.The influences of acidity of the reaction medium,starting materials,reaction temperature and reaction time on the phase composition and morphologies of NaAl(OH)₂CO₃ whiskers were discussed.The thermogravimetric analysis of the whiskers show the decomposition process in two stages,the chemical reactions for the thermal decomposition happened and release massive nonflammable gas which can absorb a large amount of heat.(2) NaAl(OH)₂CO₃/EVA compounds were prepared by melt-blending.The effect of the amount of NaAl(OH)₂CO₃ additive on the flame retardance and mechanical properties of the composites were discussed.The flame retardance mechanism of NaAl(OH)₂CO₃ was also studied by TG-DTG,SEM and FTIR.The results show that the improvement of flame retardance properties and tensile strength accompanied with increase of NaAl(OH)₂CO₃. When the content of NaAl(OH)₂CO₃ in EVA is 40%,the compounds have good performance.(3)Melamine phosphate was prepared directly with melamine and phosphoric acid in water.The effect of the reaction factors such as reaction temperature,reaction time and the amount of water were investigated.The production were characterized by chemical analysis, FTIR and TG.In the case of amount of raw materials used in this reaction the optimal conditions for preparation are gained as follows:temperature:100～120℃,water:250ml, time:3h,the mother solution could be recycled 4 times.The yield of production reaches 95.5%～96%,the phosphorus content is 13.5%,and the decomposition temperature is about 250℃.(4)The fire-retardant coatings with pure acrylic ester emulsion as binder,water as solvent, flame retardant additives and other assistants were prepared by ball milling process.The effect of different flame retardants systems and enhance fillers on charring foam layer were investigated.The flame retardance properties of the coating were tested by simulative big panel method and cone calorimeter(CONE).The results show that the coating with melamine phosphate,pentaerythritol,aluminum hydroxide and boric acid is the best one,the retardant duration is 25min.The CONE analysis results demonstrated that the heat release rate peak reduce from 338.78kW/m² to 275.49kW/m² compared with pure coating.Furthermore,the smoke production rate and total smoke production decreased obviously.