Synthesis Of Melamine Polyphosphate And Its Application In Low Density Polyethylene

Melamine phosphate (MP) with high purity was synthesized from phosphoric acid and melamine in water. The effects of the mole ratio n (melamine:phosphoric acid), reaction time, reaction temperature and the amount of water on the yield of MP have been investigated. Melamine polyphosphate (MPP) with high thermal stability was synthesized from the MP with high purity and modified melamine polyphosphate (MMPP) was prepared through thermal polymerization from MP and melamine/metal oxides/rare earth oxides. MPP and MMPP were characterized by infrared spectroscopy (IR) and thermo gravimetric analysis (TGA).The effect of MPP and MMPP on the flame-retardant properties of low density polyethylene (LDPE) has been investigated through limited oxygen index (LOI) test, cone calorimetric (cone) analysis and thermo gravimetric (TG) analysis. The flame retardant mechanism has been proposed and discussed.The results show that the optimal synthetic conditions of melamine phosphate (MP) with high purity are:the ratio of n (melamine):n (phosphoric acid) is 1:1.05, the reaction time is 36h and temperature is 95℃under 10g melamine per 100ml water. The optimal synthetic conditions of MPP are:the calcination time is 3.5h and the calcination temperature is between 280℃and 320℃. The optimal calcination conditions of MMPP are:calcination time is 3.0h and temperature is between 280℃and 320℃. The TGA results show that MMPP has better thermal stability than MPP.The LOI value of PE/MPP and PE/MMPP has been promoted to 21.56 and 22.19 which are significantly higher than that of pure PE (17.6). The char residual at 600℃for both composites are more than 10%. Cone calorimetric (cone) analysis shows MPP mainly acts in condensed phase in the combustion process of LDPE.