Preparation of modified ammonium polyphosphate and its application in flame retardant air filter paper

In order to solve the hygroscopicity of ammonium polyphosphate (APP) and improve its flame retardancy, hydrophobic and flame retardant groups were introduced on the surface of APP by means of surface coating. It was blended with styrene acrylic emulsion (AAS) as the reinforcing resin and applied to the automobile engine air filter paper. The structure of the modified particles was confirmed by FT-IR TGA showed that the initial decomposition temperature of the modified particles decreased by 15 celcius, the decomposition rate decreased by about 5%, and the carbon residue rate at 800 celcius increased from 21.73 to 44.92%; The DSC displayed that the blend resin had fine compatibility. Particle size analysis, scanning electron microscopy and transmission electron microscopy demonstrated that the large size modified APP particles were diffused into styrene acrylate emulsion particles and reconstituted to form a more compact and smaller particle size. The particles had a core shell structure with a shell thickness of 17 nm. These phenomena revealed the evolution of latex particles after blending. The air filter paper reinforced by blend resin has better mechanical properties and good water resistance. After absorbing water, the burst retention rate of air filter paper is more than 50%, and the stiffness retention rate is more than 20%. The combustion test and analysis by cone calorimeter analysis that the blend resin give the air filter paper excellent flame retardant performance.